diff --git a/src/chipset/ali1435.c b/src/chipset/ali1435.c
index aebd10f32..6619e033c 100644
--- a/src/chipset/ali1435.c
+++ b/src/chipset/ali1435.c
@@ -98,7 +98,7 @@ ali1435_update_irqs(ali1435_t *dev, int set)
 }
 
 static void
-ali1435_pci_write(int func, int addr, uint8_t val, void *priv)
+ali1435_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1435_t *dev = (ali1435_t *) priv;
     int        irq;
@@ -163,7 +163,7 @@ ali1435_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali1435_pci_read(int func, int addr, void *priv)
+ali1435_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const ali1435_t *dev = (ali1435_t *) priv;
     uint8_t          ret;
diff --git a/src/chipset/ali1489.c b/src/chipset/ali1489.c
index 96ebd4a3d..fdf0697ec 100644
--- a/src/chipset/ali1489.c
+++ b/src/chipset/ali1489.c
@@ -411,7 +411,7 @@ ali1489_read(uint16_t addr, void *priv)
 }
 
 static void
-ali1489_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+ali1489_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1489_t *dev = (ali1489_t *) priv;
 
@@ -434,7 +434,7 @@ ali1489_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali1489_pci_read(UNUSED(int func), int addr, void *priv)
+ali1489_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const ali1489_t *dev = (ali1489_t *) priv;
     uint8_t          ret = 0xff;
diff --git a/src/chipset/ali1531.c b/src/chipset/ali1531.c
index 1603dbca4..b57fe1606 100644
--- a/src/chipset/ali1531.c
+++ b/src/chipset/ali1531.c
@@ -132,7 +132,7 @@ ali1531_shadow_recalc(UNUSED(int cur_reg), ali1531_t *dev)
 }
 
 static void
-ali1531_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+ali1531_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1531_t *dev = (ali1531_t *) priv;
 
@@ -298,7 +298,7 @@ ali1531_write(UNUSED(int func), int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali1531_read(UNUSED(int func), int addr, void *priv)
+ali1531_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const ali1531_t *dev = (ali1531_t *) priv;
     uint8_t          ret = 0xff;
@@ -341,18 +341,18 @@ ali1531_reset(void *priv)
     dev->pci_conf[0x5a] = 0x20;
     dev->pci_conf[0x70] = 0x22;
 
-    ali1531_write(0, 0x42, 0x00, dev);
-    ali1531_write(0, 0x43, 0x00, dev);
+    ali1531_write(0, 0x42, 1, 0x00, dev);
+    ali1531_write(0, 0x43, 1, 0x00, dev);
 
-    ali1531_write(0, 0x47, 0x00, dev);
-    ali1531_write(0, 0x48, 0x00, dev);
+    ali1531_write(0, 0x47, 1, 0x00, dev);
+    ali1531_write(0, 0x48, 1, 0x00, dev);
 
     for (uint8_t i = 0; i < 4; i++)
-        ali1531_write(0, 0x4c + i, 0x00, dev);
+        ali1531_write(0, 0x4c + i, 1, 0x00, dev);
 
     for (uint8_t i = 0; i < 16; i += 2) {
-        ali1531_write(0, 0x60 + i, 0x08, dev);
-        ali1531_write(0, 0x61 + i, 0x40, dev);
+        ali1531_write(0, 0x60 + i, 1, 0x08, dev);
+        ali1531_write(0, 0x61 + i, 1, 0x40, dev);
     }
 }
 
diff --git a/src/chipset/ali1541.c b/src/chipset/ali1541.c
index 1506d880a..02fd51c0b 100644
--- a/src/chipset/ali1541.c
+++ b/src/chipset/ali1541.c
@@ -177,7 +177,7 @@ ali1541_mask_bar(ali1541_t *dev)
 }
 
 static void
-ali1541_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+ali1541_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1541_t *dev = (ali1541_t *) priv;
 
@@ -562,7 +562,7 @@ ali1541_write(UNUSED(int func), int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali1541_read(UNUSED(int func), int addr, void *priv)
+ali1541_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const ali1541_t *dev = (ali1541_t *) priv;
     uint8_t          ret = 0xff;
@@ -613,20 +613,20 @@ ali1541_reset(void *priv)
     dev->pci_conf[0xe0] = 0x01;
 
     cpu_cache_int_enabled = 1;
-    ali1541_write(0, 0x42, 0x00, dev);
+    ali1541_write(0, 0x42, 1, 0x00, dev);
 
-    ali1541_write(0, 0x54, 0x00, dev);
-    ali1541_write(0, 0x55, 0x00, dev);
+    ali1541_write(0, 0x54, 1, 0x00, dev);
+    ali1541_write(0, 0x55, 1, 0x00, dev);
 
     for (uint8_t i = 0; i < 4; i++)
-        ali1541_write(0, 0x56 + i, 0x00, dev);
+        ali1541_write(0, 0x56 + i, 1, 0x00, dev);
 
-    ali1541_write(0, 0x60, 0x07, dev);
-    ali1541_write(0, 0x61, 0x40, dev);
+    ali1541_write(0, 0x60, 1, 0x07, dev);
+    ali1541_write(0, 0x61, 1, 0x40, dev);
 
     for (uint8_t i = 0; i < 14; i += 2) {
-        ali1541_write(0, 0x62 + i, 0x00, dev);
-        ali1541_write(0, 0x63 + i, 0x00, dev);
+        ali1541_write(0, 0x62 + i, 1, 0x00, dev);
+        ali1541_write(0, 0x63 + i, 1, 0x00, dev);
     }
 }
 
diff --git a/src/chipset/ali1543.c b/src/chipset/ali1543.c
index 8ef8e6a20..3d5ddf603 100644
--- a/src/chipset/ali1543.c
+++ b/src/chipset/ali1543.c
@@ -112,13 +112,13 @@ ali1533_ddma_handler(UNUSED(ali1543_t *dev))
 static void ali5229_ide_handler(ali1543_t *dev);
 static void ali5229_ide_irq_handler(ali1543_t *dev);
 
-static void ali5229_write(int func, int addr, uint8_t val, void *priv);
+static void ali5229_write(int func, int addr, int len, uint8_t val, void *priv);
 
-static void    ali7101_write(int func, int addr, uint8_t val, void *priv);
-static uint8_t ali7101_read(int func, int addr, void *priv);
+static void    ali7101_write(int func, int addr, int len, uint8_t val, void *priv);
+static uint8_t ali7101_read(int func, int addr, int len, void *priv);
 
 static void
-ali1533_write(int func, int addr, uint8_t val, void *priv)
+ali1533_write(int func, int addr, int len, uint8_t val, void *priv)
 {
     ali1543_t *dev = (ali1543_t *) priv;
     ali1543_log("M1533: dev->pci_conf[%02x] = %02x\n", addr, val);
@@ -453,7 +453,7 @@ ali1533_write(int func, int addr, uint8_t val, void *priv)
         case 0x7c ... 0xff:
             if ((dev->type == 1) && !dev->pmu_dev_enable) {
                 dev->pmu_dev_enable = 1;
-                ali7101_write(func, addr, val, priv);
+                ali7101_write(func, addr, len, val, priv);
                 dev->pmu_dev_enable = 0;
             }
             break;
@@ -464,7 +464,7 @@ ali1533_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali1533_read(int func, int addr, void *priv)
+ali1533_read(int func, int addr, int len, void *priv)
 {
     ali1543_t *dev = (ali1543_t *) priv;
     uint8_t    ret = 0xff;
@@ -478,7 +478,7 @@ ali1533_read(int func, int addr, void *priv)
                 ret = (ret & 0xbf) | (dev->ide_dev_enable ? 0x40 : 0x00);
             else if ((dev->type == 1) && ((addr >= 0x7c) && (addr <= 0xff)) && !dev->pmu_dev_enable) {
                 dev->pmu_dev_enable = 1;
-                ret                 = ali7101_read(func, addr, priv);
+                ret                 = ali7101_read(func, addr, len, priv);
                 dev->pmu_dev_enable = 0;
             }
         }
@@ -690,23 +690,23 @@ ali5229_chip_reset(ali1543_t *dev)
         dev->ide_conf[0x4f] = 0x1a;
     }
 
-    ali5229_write(0, 0x04, 0x05, dev);
-    ali5229_write(0, 0x10, 0xf1, dev);
-    ali5229_write(0, 0x11, 0x01, dev);
-    ali5229_write(0, 0x14, 0xf5, dev);
-    ali5229_write(0, 0x15, 0x03, dev);
-    ali5229_write(0, 0x18, 0x71, dev);
-    ali5229_write(0, 0x19, 0x01, dev);
-    ali5229_write(0, 0x1a, 0x75, dev);
-    ali5229_write(0, 0x1b, 0x03, dev);
-    ali5229_write(0, 0x20, 0x01, dev);
-    ali5229_write(0, 0x21, 0xf0, dev);
-    ali5229_write(0, 0x4d, 0x00, dev);
+    ali5229_write(0, 0x04, 1, 0x05, dev);
+    ali5229_write(0, 0x10, 1, 0xf1, dev);
+    ali5229_write(0, 0x11, 1, 0x01, dev);
+    ali5229_write(0, 0x14, 1, 0xf5, dev);
+    ali5229_write(0, 0x15, 1, 0x03, dev);
+    ali5229_write(0, 0x18, 1, 0x71, dev);
+    ali5229_write(0, 0x19, 1, 0x01, dev);
+    ali5229_write(0, 0x1a, 1, 0x75, dev);
+    ali5229_write(0, 0x1b, 1, 0x03, dev);
+    ali5229_write(0, 0x20, 1, 0x01, dev);
+    ali5229_write(0, 0x21, 1, 0xf0, dev);
+    ali5229_write(0, 0x4d, 1, 0x00, dev);
     dev->ide_conf[0x09] = 0xfa;
-    ali5229_write(0, 0x09, 0xfa, dev);
-    ali5229_write(0, 0x52, 0x00, dev);
+    ali5229_write(0, 0x09, 1, 0xfa, dev);
+    ali5229_write(0, 0x52, 1, 0x00, dev);
 
-    ali5229_write(0, 0x50, 0x02, dev);
+    ali5229_write(0, 0x50, 1, 0x02, dev);
 
     sff_set_slot(dev->ide_controller[0], dev->ide_slot);
     sff_set_slot(dev->ide_controller[1], dev->ide_slot);
@@ -716,7 +716,7 @@ ali5229_chip_reset(ali1543_t *dev)
 }
 
 static void
-ali5229_write(int func, int addr, uint8_t val, void *priv)
+ali5229_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1543_t *dev = (ali1543_t *) priv;
     ali1543_log("M5229: [W] dev->ide_conf[%02x] = %02x\n", addr, val);
@@ -885,7 +885,7 @@ ali5229_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali5229_read(int func, int addr, void *priv)
+ali5229_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const ali1543_t *dev = (ali1543_t *) priv;
     uint8_t    ret = 0xff;
@@ -908,7 +908,7 @@ ali5229_read(int func, int addr, void *priv)
 }
 
 static void
-ali5237_write(int func, int addr, uint8_t val, void *priv)
+ali5237_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1543_t *dev = (ali1543_t *) priv;
     ali1543_log("M5237: dev->usb_conf[%02x] = %02x\n", addr, val);
@@ -975,7 +975,7 @@ ali5237_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali5237_read(int func, int addr, void *priv)
+ali5237_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const ali1543_t *dev = (ali1543_t *) priv;
     uint8_t    ret = 0xff;
@@ -987,7 +987,7 @@ ali5237_read(int func, int addr, void *priv)
 }
 
 static void
-ali7101_write(int func, int addr, uint8_t val, void *priv)
+ali7101_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1543_t *dev = (ali1543_t *) priv;
     ali1543_log("M7101: [W] dev->pmu_conf[%02x] = %02x\n", addr, val);
@@ -1408,7 +1408,7 @@ ali7101_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali7101_read(int func, int addr, void *priv)
+ali7101_read(int func, int addr, UNUSED(int len), void *priv)
 {
     ali1543_t *dev = (ali1543_t *) priv;
     uint8_t    ret = 0xff;
@@ -1516,11 +1516,11 @@ ali1543_reset(void *priv)
     dev->usb_conf[0x0b] = 0x0c;
     dev->usb_conf[0x3d] = 0x01;
 
-    ali5237_write(0, 0x04, 0x00, dev);
-    ali5237_write(0, 0x10, 0x00, dev);
-    ali5237_write(0, 0x11, 0x00, dev);
-    ali5237_write(0, 0x12, 0x00, dev);
-    ali5237_write(0, 0x13, 0x00, dev);
+    ali5237_write(0, 0x04, 1, 0x00, dev);
+    ali5237_write(0, 0x10, 1, 0x00, dev);
+    ali5237_write(0, 0x11, 1, 0x00, dev);
+    ali5237_write(0, 0x12, 1, 0x00, dev);
+    ali5237_write(0, 0x13, 1, 0x00, dev);
 
     /* M7101 */
     memset(dev->pmu_conf, 0x00, sizeof(dev->pmu_conf));
@@ -1536,26 +1536,26 @@ ali1543_reset(void *priv)
     acpi_set_slot(dev->acpi, dev->pmu_slot);
     acpi_set_nvr(dev->acpi, dev->nvr);
 
-    ali7101_write(0, 0x04, 0x0f, dev);
-    ali7101_write(0, 0x10, 0x01, dev);
-    ali7101_write(0, 0x11, 0x00, dev);
-    ali7101_write(0, 0x12, 0x00, dev);
-    ali7101_write(0, 0x13, 0x00, dev);
-    ali7101_write(0, 0x14, 0x01, dev);
-    ali7101_write(0, 0x15, 0x00, dev);
-    ali7101_write(0, 0x16, 0x00, dev);
-    ali7101_write(0, 0x17, 0x00, dev);
-    ali7101_write(0, 0x40, 0x00, dev);
-    ali7101_write(0, 0x41, 0x00, dev);
-    ali7101_write(0, 0x42, 0x00, dev);
-    ali7101_write(0, 0x43, 0x00, dev);
-    ali7101_write(0, 0x77, 0x00, dev);
-    ali7101_write(0, 0xbd, 0x00, dev);
-    ali7101_write(0, 0xc0, 0x00, dev);
-    ali7101_write(0, 0xc1, 0x00, dev);
-    ali7101_write(0, 0xc2, 0x00, dev);
-    ali7101_write(0, 0xc3, 0x00, dev);
-    ali7101_write(0, 0xe0, 0x00, dev);
+    ali7101_write(0, 0x04, 1, 0x0f, dev);
+    ali7101_write(0, 0x10, 1, 0x01, dev);
+    ali7101_write(0, 0x11, 1, 0x00, dev);
+    ali7101_write(0, 0x12, 1, 0x00, dev);
+    ali7101_write(0, 0x13, 1, 0x00, dev);
+    ali7101_write(0, 0x14, 1, 0x01, dev);
+    ali7101_write(0, 0x15, 1, 0x00, dev);
+    ali7101_write(0, 0x16, 1, 0x00, dev);
+    ali7101_write(0, 0x17, 1, 0x00, dev);
+    ali7101_write(0, 0x40, 1, 0x00, dev);
+    ali7101_write(0, 0x41, 1, 0x00, dev);
+    ali7101_write(0, 0x42, 1, 0x00, dev);
+    ali7101_write(0, 0x43, 1, 0x00, dev);
+    ali7101_write(0, 0x77, 1, 0x00, dev);
+    ali7101_write(0, 0xbd, 1, 0x00, dev);
+    ali7101_write(0, 0xc0, 1, 0x00, dev);
+    ali7101_write(0, 0xc1, 1, 0x00, dev);
+    ali7101_write(0, 0xc2, 1, 0x00, dev);
+    ali7101_write(0, 0xc3, 1, 0x00, dev);
+    ali7101_write(0, 0xe0, 1, 0x00, dev);
 
     /* Do the bridge last due to device deactivations. */
     /* M1533 */
@@ -1570,19 +1570,19 @@ ali1543_reset(void *priv)
     dev->pci_conf[0x0a] = 0x01;
     dev->pci_conf[0x0b] = 0x06;
 
-    ali1533_write(0, 0x41, 0x00, dev);    /* Disables the keyboard and mouse IRQ latch. */
-    ali1533_write(0, 0x48, 0x00, dev);    /* Disables all IRQ's. */
-    ali1533_write(0, 0x44, 0x00, dev);
-    ali1533_write(0, 0x4d, 0x00, dev);
-    ali1533_write(0, 0x53, 0x00, dev);
-    ali1533_write(0, 0x58, 0x00, dev);
-    ali1533_write(0, 0x5f, 0x00, dev);
-    ali1533_write(0, 0x72, 0x00, dev);
-    ali1533_write(0, 0x74, 0x00, dev);
-    ali1533_write(0, 0x75, 0x00, dev);
-    ali1533_write(0, 0x76, 0x00, dev);
+    ali1533_write(0, 0x41, 1, 0x00, dev);    /* Disables the keyboard and mouse IRQ latch. */
+    ali1533_write(0, 0x48, 1, 0x00, dev);    /* Disables all IRQ's. */
+    ali1533_write(0, 0x44, 1, 0x00, dev);
+    ali1533_write(0, 0x4d, 1, 0x00, dev);
+    ali1533_write(0, 0x53, 1, 0x00, dev);
+    ali1533_write(0, 0x58, 1, 0x00, dev);
+    ali1533_write(0, 0x5f, 1, 0x00, dev);
+    ali1533_write(0, 0x72, 1, 0x00, dev);
+    ali1533_write(0, 0x74, 1, 0x00, dev);
+    ali1533_write(0, 0x75, 1, 0x00, dev);
+    ali1533_write(0, 0x76, 1, 0x00, dev);
     if (dev->type == 1)
-        ali1533_write(0, 0x78, 0x00, dev);
+        ali1533_write(0, 0x78, 1, 0x00, dev);
 
     unmask_a20_in_smm = 1;
 }
diff --git a/src/chipset/ali1621.c b/src/chipset/ali1621.c
index 95602496c..217c1b865 100644
--- a/src/chipset/ali1621.c
+++ b/src/chipset/ali1621.c
@@ -255,7 +255,7 @@ ali1621_mask_bar(ali1621_t *dev)
 }
 
 static void
-ali1621_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+ali1621_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ali1621_t *dev = (ali1621_t *) priv;
 
@@ -581,7 +581,7 @@ ali1621_write(UNUSED(int func), int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ali1621_read(UNUSED(int func), int addr, void *priv)
+ali1621_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const ali1621_t *dev = (ali1621_t *) priv;
     uint8_t          ret = 0xff;
@@ -647,10 +647,10 @@ ali1621_reset(void *priv)
     dev->pci_conf[0xf2] = dev->pci_conf[0xf6] = dev->pci_conf[0xfa] = dev->pci_conf[0xfe] = 0x21;
     dev->pci_conf[0xf3] = dev->pci_conf[0xf7] = dev->pci_conf[0xfb] = dev->pci_conf[0xff] = 0x43;
 
-    ali1621_write(0, 0x83, 0x08, dev);
+    ali1621_write(0, 0x83, 1, 0x08, dev);
 
     for (uint8_t i = 0; i < 4; i++)
-        ali1621_write(0, 0x84 + i, 0x00, dev);
+        ali1621_write(0, 0x84 + i, 1, 0x00, dev);
 }
 
 static void
diff --git a/src/chipset/ims8848.c b/src/chipset/ims8848.c
index 13fed304b..16625f3a1 100644
--- a/src/chipset/ims8848.c
+++ b/src/chipset/ims8848.c
@@ -292,7 +292,7 @@ ims8848_read(uint16_t addr, void *priv)
 }
 
 static void
-ims8849_pci_write(int func, int addr, uint8_t val, void *priv)
+ims8849_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ims8848_t *dev = (ims8848_t *) priv;
 
@@ -326,7 +326,7 @@ ims8849_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-ims8849_pci_read(int func, int addr, void *priv)
+ims8849_pci_read(int func, UNUSED(int len), int addr, void *priv)
 {
     const ims8848_t *dev = (ims8848_t *) priv;
     uint8_t          ret = 0xff;
diff --git a/src/chipset/intel_420ex.c b/src/chipset/intel_420ex.c
index daa55c72c..67e2ae069 100644
--- a/src/chipset/intel_420ex.c
+++ b/src/chipset/intel_420ex.c
@@ -183,7 +183,7 @@ i420ex_drb_recalc(i420ex_t *dev)
 
 
 static void
-i420ex_write(int func, int addr, uint8_t val, void *priv)
+i420ex_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     i420ex_t *dev = (i420ex_t *) priv;
 
@@ -397,7 +397,7 @@ i420ex_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-i420ex_read(int func, int addr, void *priv)
+i420ex_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const i420ex_t *dev = (i420ex_t *) priv;
     uint8_t         ret;
@@ -472,31 +472,31 @@ i420ex_reset(void *priv)
 {
     i420ex_t *dev = (i420ex_t *) priv;
 
-    i420ex_write(0, 0x48, 0x00, priv);
+    i420ex_write(0, 0x48, 1, 0x00, priv);
 
     /* Disable the PIC mouse latch. */
-    i420ex_write(0, 0x4e, 0x03, priv);
+    i420ex_write(0, 0x4e, 1, 0x03, priv);
 
     for (uint8_t i = 0; i < 7; i++)
-        i420ex_write(0, 0x59 + i, 0x00, priv);
+        i420ex_write(0, 0x59 + i, 1, 0x00, priv);
 
     for (uint8_t i = 0; i <= 4; i++)
         dev->regs[0x60 + i] = 0x01;
 
     dev->regs[0x70] &= 0xef; /* Forcibly unlock the SMRAM register. */
     dev->smram_locked = 0;
-    i420ex_write(0, 0x70, 0x00, priv);
+    i420ex_write(0, 0x70, 1, 0x00, priv);
 
     mem_set_mem_state(0x000a0000, 0x00060000, MEM_READ_EXTANY | MEM_WRITE_EXTANY);
     mem_set_mem_state_smm(0x000a0000, 0x00060000, MEM_READ_EXTANY | MEM_WRITE_EXTANY);
 
-    i420ex_write(0, 0xa0, 0x08, priv);
-    i420ex_write(0, 0xa2, 0x00, priv);
-    i420ex_write(0, 0xa4, 0x00, priv);
-    i420ex_write(0, 0xa5, 0x00, priv);
-    i420ex_write(0, 0xa6, 0x00, priv);
-    i420ex_write(0, 0xa7, 0x00, priv);
-    i420ex_write(0, 0xa8, 0x0f, priv);
+    i420ex_write(0, 0xa0, 1, 0x08, priv);
+    i420ex_write(0, 0xa2, 1, 0x00, priv);
+    i420ex_write(0, 0xa4, 1, 0x00, priv);
+    i420ex_write(0, 0xa5, 1, 0x00, priv);
+    i420ex_write(0, 0xa6, 1, 0x00, priv);
+    i420ex_write(0, 0xa7, 1, 0x00, priv);
+    i420ex_write(0, 0xa8, 1, 0x0f, priv);
 }
 
 static void
diff --git a/src/chipset/intel_4x0.c b/src/chipset/intel_4x0.c
index 18f4ee66a..48627e39b 100644
--- a/src/chipset/intel_4x0.c
+++ b/src/chipset/intel_4x0.c
@@ -243,7 +243,7 @@ pm2_cntrl_write(UNUSED(uint16_t addr), uint8_t val, void *priv)
 }
 
 static void
-i4x0_write(int func, int addr, uint8_t val, void *priv)
+i4x0_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     i4x0_t  *dev    = (i4x0_t *) priv;
     uint8_t *regs   = (uint8_t *) dev->regs;
@@ -1535,7 +1535,7 @@ i4x0_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-i4x0_read(int func, int addr, void *priv)
+i4x0_read(int func, int addr, UNUSED(int len), void *priv)
 {
     i4x0_t        *dev  = (i4x0_t *) priv;
     uint8_t        ret  = 0xff;
@@ -1563,12 +1563,12 @@ i4x0_reset(void *priv)
         memset(dev->regs_locked, 0x00, 256 * sizeof(uint8_t));
 
     if (dev->type >= INTEL_430FX)
-        i4x0_write(0, 0x59, 0x00, priv);
+        i4x0_write(0, 0x59, 1, 0x00, priv);
     else
-        i4x0_write(0, 0x59, 0x0f, priv);
+        i4x0_write(0, 0x59, 1, 0x0f, priv);
 
     for (uint8_t i = 0; i < 6; i++)
-        i4x0_write(0, 0x5a + i, 0x00, priv);
+        i4x0_write(0, 0x5a + i, 1, 0x00, priv);
 
     for (uint8_t i = 0; i <= dev->max_drb; i++)
         dev->regs[0x60 + i] = dev->drb_default;
@@ -1582,18 +1582,18 @@ i4x0_reset(void *priv)
 
     if (dev->type >= INTEL_430FX) {
         dev->regs[0x72] &= 0xef; /* Forcibly unlock the SMRAM register. */
-        i4x0_write(0, 0x72, 0x02, priv);
+        i4x0_write(0, 0x72, 1, 0x02, priv);
     } else if (dev->type >= INTEL_430LX) {
         dev->regs[0x72] &= 0xf7; /* Forcibly unlock the SMRAM register. */
-        i4x0_write(0, 0x72, 0x00, priv);
+        i4x0_write(0, 0x72, 1, 0x00, priv);
     } else {
         dev->regs[0x57] &= 0xef; /* Forcibly unlock the SMRAM register. */
-        i4x0_write(0, 0x57, 0x02, priv);
+        i4x0_write(0, 0x57, 1, 0x02, priv);
     }
 
     if ((dev->type == INTEL_430TX) || (dev->type >= INTEL_440BX)) {
         i4x0_write(0, (dev->type >= INTEL_440BX) ? 0x73 : 0x71,
-                   (dev->type >= INTEL_440BX) ? 0x38 : 0x00, priv);
+                   1, (dev->type >= INTEL_440BX) ? 0x38 : 0x00, priv);
     }
 }
 
@@ -1932,24 +1932,24 @@ i4x0_init(const device_t *info)
     else if (dev->type >= INTEL_440LX)
         cpu_set_agp_speed(cpu_busspeed);
 
-    i4x0_write(regs[0x59], 0x59, 0x00, dev);
-    i4x0_write(regs[0x5a], 0x5a, 0x00, dev);
-    i4x0_write(regs[0x5b], 0x5b, 0x00, dev);
-    i4x0_write(regs[0x5c], 0x5c, 0x00, dev);
-    i4x0_write(regs[0x5d], 0x5d, 0x00, dev);
-    i4x0_write(regs[0x5e], 0x5e, 0x00, dev);
-    i4x0_write(regs[0x5f], 0x5f, 0x00, dev);
+    i4x0_write(regs[0x59], 0x59, 1, 0x00, dev);
+    i4x0_write(regs[0x5a], 0x5a, 1, 0x00, dev);
+    i4x0_write(regs[0x5b], 0x5b, 1, 0x00, dev);
+    i4x0_write(regs[0x5c], 0x5c, 1, 0x00, dev);
+    i4x0_write(regs[0x5d], 0x5d, 1, 0x00, dev);
+    i4x0_write(regs[0x5e], 0x5e, 1, 0x00, dev);
+    i4x0_write(regs[0x5f], 0x5f, 1, 0x00, dev);
 
     if (dev->type >= INTEL_430FX)
-        i4x0_write(0, 0x72, 0x02, dev);
+        i4x0_write(0, 0x72, 1, 0x02, dev);
     else if (dev->type >= INTEL_430LX)
-        i4x0_write(0, 0x72, 0x00, dev);
+        i4x0_write(0, 0x72, 1, 0x00, dev);
     else
-        i4x0_write(0, 0x57, 0x02, dev);
+        i4x0_write(0, 0x57, 1, 0x02, dev);
 
     if ((dev->type == INTEL_430TX) || (dev->type >= INTEL_440BX)) {
         i4x0_write(0, (dev->type >= INTEL_440BX) ? 0x73 : 0x71,
-                   (dev->type >= INTEL_440BX) ? 0x38 : 0x00, dev);
+                   1, (dev->type >= INTEL_440BX) ? 0x38 : 0x00, dev);
     }
 
     pci_add_card(PCI_ADD_NORTHBRIDGE, i4x0_read, i4x0_write, dev, &dev->pci_slot);
diff --git a/src/chipset/intel_i450kx.c b/src/chipset/intel_i450kx.c
index 34cc6a62f..cb793179a 100644
--- a/src/chipset/intel_i450kx.c
+++ b/src/chipset/intel_i450kx.c
@@ -126,7 +126,7 @@ i450kx_vid_buf_recalc(i450kx_t *dev, int bus)
 }
 
 static void
-pb_write(int func, int addr, uint8_t val, void *priv)
+pb_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     i450kx_t *dev = (i450kx_t *) priv;
 
@@ -371,7 +371,7 @@ pb_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-pb_read(int func, int addr, void *priv)
+pb_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const i450kx_t *dev = (i450kx_t *) priv;
     uint8_t   ret = 0xff;
@@ -400,7 +400,7 @@ mc_fill_drbs(i450kx_t *dev)
 }
 
 static void
-mc_write(int func, int addr, uint8_t val, void *priv)
+mc_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     i450kx_t *dev = (i450kx_t *) priv;
 
@@ -601,7 +601,7 @@ mc_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-mc_read(int func, int addr, void *priv)
+mc_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const i450kx_t *dev = (i450kx_t *) priv;
     uint8_t   ret = 0xff;
@@ -707,9 +707,9 @@ i450kx_reset(void *priv)
 #endif
     i450kx_smram_recalc(dev, 1);
     i450kx_vid_buf_recalc(dev, 1);
-    pb_write(0, 0x59, 0x30, dev);
+    pb_write(0, 0x59, 1, 0x30, dev);
     for (i = 0x5a; i <= 0x5f; i++)
-        pb_write(0, i, 0x33, dev);
+        pb_write(0, i, 1, 0x33, dev);
 
     /* Defaults MC */
     dev->mc_pci_conf[0x00] = 0x86;
@@ -779,9 +779,9 @@ i450kx_reset(void *priv)
 
     i450kx_smram_recalc(dev, 0);
     i450kx_vid_buf_recalc(dev, 0);
-    mc_write(0, 0x59, 0x03, dev);
+    mc_write(0, 0x59, 1, 0x03, dev);
     for (i = 0x5a; i <= 0x5f; i++)
-        mc_write(0, i, 0x00, dev);
+        mc_write(0, i, 1, 0x00, dev);
     for (i = 0x60; i <= 0x6f; i++)
         dev->mc_pci_conf[i] = 0x01;
 }
diff --git a/src/chipset/intel_piix.c b/src/chipset/intel_piix.c
index 9d4d88687..9f7814869 100644
--- a/src/chipset/intel_piix.c
+++ b/src/chipset/intel_piix.c
@@ -464,7 +464,7 @@ piix_trap_update(void *priv)
 }
 
 static void
-piix_write(int func, int addr, uint8_t val, void *priv)
+piix_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     piix_t  *dev = (piix_t *) priv;
     uint8_t *fregs;
@@ -1192,7 +1192,7 @@ piix_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-piix_read(int func, int addr, void *priv)
+piix_read(int func, int addr, UNUSED(int len), void *priv)
 {
     piix_t        *dev = (piix_t *) priv;
     uint8_t        ret = 0xff;
@@ -1447,68 +1447,68 @@ piix_reset(void *priv)
     const piix_t *dev = (piix_t *) priv;
 
     if (dev->type > 3) {
-        piix_write(3, 0x04, 0x00, priv);
-        piix_write(3, 0x5b, 0x00, priv);
+        piix_write(3, 0x04, 1, 0x00, priv);
+        piix_write(3, 0x5b, 1, 0x00, priv);
     } else {
-        piix_write(0, 0xa0, 0x08, priv);
-        piix_write(0, 0xa2, 0x00, priv);
-        piix_write(0, 0xa4, 0x00, priv);
-        piix_write(0, 0xa5, 0x00, priv);
-        piix_write(0, 0xa6, 0x00, priv);
-        piix_write(0, 0xa7, 0x00, priv);
-        piix_write(0, 0xa8, 0x0f, priv);
+        piix_write(0, 0xa0, 1, 0x08, priv);
+        piix_write(0, 0xa2, 1, 0x00, priv);
+        piix_write(0, 0xa4, 1, 0x00, priv);
+        piix_write(0, 0xa5, 1, 0x00, priv);
+        piix_write(0, 0xa6, 1, 0x00, priv);
+        piix_write(0, 0xa7, 1, 0x00, priv);
+        piix_write(0, 0xa8, 1, 0x0f, priv);
     }
 
     /* Disable the PIC mouse latch. */
-    piix_write(0, 0x4e, 0x03, priv);
+    piix_write(0, 0x4e, 1, 0x03, priv);
 
     if (dev->type == 5)
-        piix_write(0, 0xe1, 0x40, priv);
-    piix_write(1, 0x04, 0x00, priv);
+        piix_write(0, 0xe1, 1, 0x40, priv);
+    piix_write(1, 0x04, 1, 0x00, priv);
     if (dev->type == 5) {
-        piix_write(1, 0x09, 0x8a, priv);
-        piix_write(1, 0x10, 0xf1, priv);
-        piix_write(1, 0x11, 0x01, priv);
-        piix_write(1, 0x14, 0xf5, priv);
-        piix_write(1, 0x15, 0x03, priv);
-        piix_write(1, 0x18, 0x71, priv);
-        piix_write(1, 0x19, 0x01, priv);
-        piix_write(1, 0x1c, 0x75, priv);
-        piix_write(1, 0x1d, 0x03, priv);
+        piix_write(1, 0x09, 1, 0x8a, priv);
+        piix_write(1, 0x10, 1, 0xf1, priv);
+        piix_write(1, 0x11, 1, 0x01, priv);
+        piix_write(1, 0x14, 1, 0xf5, priv);
+        piix_write(1, 0x15, 1, 0x03, priv);
+        piix_write(1, 0x18, 1, 0x71, priv);
+        piix_write(1, 0x19, 1, 0x01, priv);
+        piix_write(1, 0x1c, 1, 0x75, priv);
+        piix_write(1, 0x1d, 1, 0x03, priv);
     } else
-        piix_write(1, 0x09, 0x80, priv);
-    piix_write(1, 0x20, 0x01, priv);
-    piix_write(1, 0x21, 0x00, priv);
-    piix_write(1, 0x41, 0x00, priv);
-    piix_write(1, 0x43, 0x00, priv);
+        piix_write(1, 0x09, 1, 0x80, priv);
+    piix_write(1, 0x20, 1, 0x01, priv);
+    piix_write(1, 0x21, 1, 0x00, priv);
+    piix_write(1, 0x41, 1, 0x00, priv);
+    piix_write(1, 0x43, 1, 0x00, priv);
 
     ide_pri_disable();
     ide_sec_disable();
 
     if (dev->type >= 3) {
-        piix_write(2, 0x04, 0x00, priv);
+        piix_write(2, 0x04, 1, 0x00, priv);
         if (dev->type == 5) {
-            piix_write(2, 0x10, 0x00, priv);
-            piix_write(2, 0x11, 0x00, priv);
-            piix_write(2, 0x12, 0x00, priv);
-            piix_write(2, 0x13, 0x00, priv);
+            piix_write(2, 0x10, 1, 0x00, priv);
+            piix_write(2, 0x11, 1, 0x00, priv);
+            piix_write(2, 0x12, 1, 0x00, priv);
+            piix_write(2, 0x13, 1, 0x00, priv);
         } else {
-            piix_write(2, 0x20, 0x01, priv);
-            piix_write(2, 0x21, 0x00, priv);
-            piix_write(2, 0x22, 0x00, priv);
-            piix_write(2, 0x23, 0x00, priv);
+            piix_write(2, 0x20, 1, 0x01, priv);
+            piix_write(2, 0x21, 1, 0x00, priv);
+            piix_write(2, 0x22, 1, 0x00, priv);
+            piix_write(2, 0x23, 1, 0x00, priv);
         }
     }
 
     if (dev->type >= 4) {
-        piix_write(0, 0xb0, is_pentium ? 0x00 : 0x04, priv);
-        piix_write(3, 0x40, 0x01, priv);
-        piix_write(3, 0x41, 0x00, priv);
-        piix_write(3, 0x5b, 0x00, priv);
-        piix_write(3, 0x80, 0x00, priv);
-        piix_write(3, 0x90, 0x01, priv);
-        piix_write(3, 0x91, 0x00, priv);
-        piix_write(3, 0xd2, 0x00, priv);
+        piix_write(0, 0xb0, 1, is_pentium ? 0x00 : 0x04, priv);
+        piix_write(3, 0x40, 1, 0x01, priv);
+        piix_write(3, 0x41, 1, 0x00, priv);
+        piix_write(3, 0x5b, 1, 0x00, priv);
+        piix_write(3, 0x80, 1, 0x00, priv);
+        piix_write(3, 0x90, 1, 0x01, priv);
+        piix_write(3, 0x91, 1, 0x00, priv);
+        piix_write(3, 0xd2, 1, 0x00, priv);
     }
 
     sff_set_irq_mode(dev->bm[0], IRQ_MODE_LEGACY);
diff --git a/src/chipset/intel_sio.c b/src/chipset/intel_sio.c
index 739785acb..c28fa5471 100644
--- a/src/chipset/intel_sio.c
+++ b/src/chipset/intel_sio.c
@@ -135,7 +135,7 @@ sio_timer_readw(uint16_t addr, void *priv)
 }
 
 static void
-sio_write(int func, int addr, uint8_t val, void *priv)
+sio_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     sio_t  *dev = (sio_t *) priv;
     uint8_t old;
@@ -324,7 +324,7 @@ sio_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sio_read(int func, int addr, void *priv)
+sio_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sio_t  *dev = (sio_t *) priv;
     uint8_t       ret;
@@ -473,20 +473,20 @@ sio_reset(void *priv)
     const sio_t *dev = (sio_t *) priv;
 
     /* Disable the PIC mouse latch. */
-    sio_write(0, 0x4d, 0x40, priv);
+    sio_write(0, 0x4d, 1, 0x40, priv);
 
-    sio_write(0, 0x57, 0x04, priv);
+    sio_write(0, 0x57, 1, 0x04, priv);
 
     dma_set_params(1, 0xffffffff);
 
     if (dev->id == 0x03) {
-        sio_write(0, 0xa0, 0x08, priv);
-        sio_write(0, 0xa2, 0x00, priv);
-        sio_write(0, 0xa4, 0x00, priv);
-        sio_write(0, 0xa5, 0x00, priv);
-        sio_write(0, 0xa6, 0x00, priv);
-        sio_write(0, 0xa7, 0x00, priv);
-        sio_write(0, 0xa8, 0x0f, priv);
+        sio_write(0, 0xa0, 1, 0x08, priv);
+        sio_write(0, 0xa2, 1, 0x00, priv);
+        sio_write(0, 0xa4, 1, 0x00, priv);
+        sio_write(0, 0xa5, 1, 0x00, priv);
+        sio_write(0, 0xa6, 1, 0x00, priv);
+        sio_write(0, 0xa7, 1, 0x00, priv);
+        sio_write(0, 0xa8, 1, 0x0f, priv);
     }
 }
 
diff --git a/src/chipset/opti822.c b/src/chipset/opti822.c
index 2f416a1c2..2029a6b40 100644
--- a/src/chipset/opti822.c
+++ b/src/chipset/opti822.c
@@ -48,7 +48,6 @@ typedef struct opti822_t {
     uint8_t pci_regs[256];
 } opti822_t;
 
-// #define ENABLE_OPTI822_LOG 1
 #ifdef ENABLE_OPTI822_LOG
 int opti822_do_log = ENABLE_OPTI822_LOG;
 
@@ -131,7 +130,7 @@ opti822_update_irqs(opti822_t *dev, int set)
 }
 
 static void
-opti822_pci_write(int func, int addr, uint8_t val, void *priv)
+opti822_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     opti822_t *dev = (opti822_t *) priv;
     int        irq;
@@ -336,7 +335,7 @@ opti822_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-opti822_pci_read(int func, int addr, void *priv)
+opti822_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const opti822_t *dev = (opti822_t *) priv;
     uint8_t          ret;
diff --git a/src/chipset/sis_5511.c b/src/chipset/sis_5511.c
index 38fcfe717..c22f798af 100644
--- a/src/chipset/sis_5511.c
+++ b/src/chipset/sis_5511.c
@@ -76,7 +76,7 @@ typedef struct sis_5511_t {
 } sis_5511_t;
 
 static void
-sis_5511_write(int func, int addr, uint8_t val, void *priv)
+sis_5511_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5511_t *dev = (sis_5511_t *) priv;
 
@@ -87,7 +87,7 @@ sis_5511_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5511_read(int func, int addr, void *priv)
+sis_5511_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5511_t *dev = (sis_5511_t *) priv;
     uint8_t ret = 0xff;
@@ -101,7 +101,7 @@ sis_5511_read(int func, int addr, void *priv)
 }
 
 static void
-sis_5513_write(int func, int addr, uint8_t val, void *priv)
+sis_5513_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5511_t *dev = (sis_5511_t *) priv;
 
@@ -114,7 +114,7 @@ sis_5513_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5513_read(int func, int addr, void *priv)
+sis_5513_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5511_t *dev = (sis_5511_t *) priv;
     uint8_t ret = 0xff;
diff --git a/src/chipset/sis_5571.c b/src/chipset/sis_5571.c
index 02e86a98a..824f1f338 100644
--- a/src/chipset/sis_5571.c
+++ b/src/chipset/sis_5571.c
@@ -75,7 +75,7 @@ typedef struct sis_5571_t {
 } sis_5571_t;
 
 static void
-sis_5571_write(int func, int addr, uint8_t val, void *priv)
+sis_5571_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5571_t *dev = (sis_5571_t *) priv;
 
@@ -86,7 +86,7 @@ sis_5571_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5571_read(int func, int addr, void *priv)
+sis_5571_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5571_t *dev = (sis_5571_t *) priv;
     uint8_t ret = 0xff;
@@ -100,7 +100,7 @@ sis_5571_read(int func, int addr, void *priv)
 }
 
 static void
-sis_5572_write(int func, int addr, uint8_t val, void *priv)
+sis_5572_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5571_t *dev = (sis_5571_t *) priv;
 
@@ -120,7 +120,7 @@ sis_5572_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5572_read(int func, int addr, void *priv)
+sis_5572_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5571_t *dev = (sis_5571_t *) priv;
     uint8_t ret = 0xff;
diff --git a/src/chipset/sis_5581.c b/src/chipset/sis_5581.c
index 525fe6598..ea54a407b 100644
--- a/src/chipset/sis_5581.c
+++ b/src/chipset/sis_5581.c
@@ -75,7 +75,7 @@ typedef struct sis_5581_t {
 } sis_5581_t;
 
 static void
-sis_5581_write(int func, int addr, uint8_t val, void *priv)
+sis_5581_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5581_t *dev = (sis_5581_t *) priv;
 
@@ -86,7 +86,7 @@ sis_5581_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5581_read(int func, int addr, void *priv)
+sis_5581_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5581_t *dev = (sis_5581_t *) priv;
     uint8_t ret = 0xff;
@@ -100,7 +100,7 @@ sis_5581_read(int func, int addr, void *priv)
 }
 
 static void
-sis_5582_write(int func, int addr, uint8_t val, void *priv)
+sis_5582_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5581_t *dev = (sis_5581_t *) priv;
 
@@ -120,7 +120,7 @@ sis_5582_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5582_read(int func, int addr, void *priv)
+sis_5582_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5581_t *dev = (sis_5581_t *) priv;
     uint8_t ret = 0xff;
diff --git a/src/chipset/sis_5591.c b/src/chipset/sis_5591.c
index d814e0f74..48cbe9765 100644
--- a/src/chipset/sis_5591.c
+++ b/src/chipset/sis_5591.c
@@ -76,7 +76,7 @@ typedef struct sis_5591_t {
 } sis_5591_t;
 
 static void
-sis_5591_write(int func, int addr, uint8_t val, void *priv)
+sis_5591_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5591_t *dev = (sis_5591_t *) priv;
 
@@ -89,7 +89,7 @@ sis_5591_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5591_read(int func, int addr, void *priv)
+sis_5591_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5591_t *dev = (sis_5591_t *) priv;
     uint8_t ret = 0xff;
@@ -105,7 +105,7 @@ sis_5591_read(int func, int addr, void *priv)
 }
 
 static void
-sis_5595_write(int func, int addr, uint8_t val, void *priv)
+sis_5595_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5591_t *dev = (sis_5591_t *) priv;
 
@@ -125,7 +125,7 @@ sis_5595_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5595_read(int func, int addr, void *priv)
+sis_5595_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5591_t *dev = (sis_5591_t *) priv;
     uint8_t ret = 0xff;
diff --git a/src/chipset/sis_5600.c b/src/chipset/sis_5600.c
index 564243c68..2610ea88f 100644
--- a/src/chipset/sis_5600.c
+++ b/src/chipset/sis_5600.c
@@ -76,7 +76,7 @@ typedef struct sis_5600_t {
 } sis_5600_t;
 
 static void
-sis_5600_write(int func, int addr, uint8_t val, void *priv)
+sis_5600_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5600_t *dev = (sis_5600_t *) priv;
 
@@ -89,7 +89,7 @@ sis_5600_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5600_read(int func, int addr, void *priv)
+sis_5600_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5600_t *dev = (sis_5600_t *) priv;
     uint8_t ret = 0xff;
@@ -105,7 +105,7 @@ sis_5600_read(int func, int addr, void *priv)
 }
 
 static void
-sis_5595_write(int func, int addr, uint8_t val, void *priv)
+sis_5595_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     const sis_5600_t *dev = (sis_5600_t *) priv;
 
@@ -125,7 +125,7 @@ sis_5595_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_5595_read(int func, int addr, void *priv)
+sis_5595_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_5600_t *dev = (sis_5600_t *) priv;
     uint8_t ret = 0xff;
diff --git a/src/chipset/sis_85c496.c b/src/chipset/sis_85c496.c
index f2c1941d4..a04f01633 100644
--- a/src/chipset/sis_85c496.c
+++ b/src/chipset/sis_85c496.c
@@ -216,7 +216,7 @@ sis_85c496_drb_recalc(sis_85c496_t *dev)
 
 /* 00 - 3F = PCI Configuration, 40 - 7F = 85C496, 80 - FF = 85C497 */
 static void
-sis_85c49x_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+sis_85c49x_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     sis_85c496_t *dev = (sis_85c496_t *) priv;
     uint8_t       old;
@@ -507,7 +507,7 @@ sis_85c49x_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_85c49x_pci_read(UNUSED(int func), int addr, void *priv)
+sis_85c49x_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const sis_85c496_t *dev = (sis_85c496_t *) priv;
     uint8_t             ret = dev->pci_conf[addr];
@@ -577,35 +577,35 @@ sis_85c496_reset(void *priv)
 {
     sis_85c496_t *dev = (sis_85c496_t *) priv;
 
-    sis_85c49x_pci_write(0, 0x44, 0x00, dev);
-    sis_85c49x_pci_write(0, 0x45, 0x00, dev);
-    sis_85c49x_pci_write(0, 0x58, 0x00, dev);
-    sis_85c49x_pci_write(0, 0x59, 0x00, dev);
-    sis_85c49x_pci_write(0, 0x5a, 0x00, dev);
-    // sis_85c49x_pci_write(0, 0x5a, 0x06, dev);
+    sis_85c49x_pci_write(0, 0x44, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x45, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x58, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x59, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x5a, 1, 0x00, dev);
+    // sis_85c49x_pci_write(0, 0x5a, 1, 0x06, dev);
 
     for (uint8_t i = 0; i < 8; i++)
         dev->pci_conf[0x48 + i] = 0x02;
 
-    sis_85c49x_pci_write(0, 0x80, 0x00, dev);
-    sis_85c49x_pci_write(0, 0x81, 0x00, dev);
-    sis_85c49x_pci_write(0, 0x9e, 0x00, dev);
-    sis_85c49x_pci_write(0, 0x8d, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xa0, 0xff, dev);
-    sis_85c49x_pci_write(0, 0xa1, 0xff, dev);
-    sis_85c49x_pci_write(0, 0xc0, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xc1, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xc2, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xc3, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xc8, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xc9, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xca, 0x00, dev);
-    sis_85c49x_pci_write(0, 0xcb, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x80, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x81, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x9e, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0x8d, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xa0, 1, 0xff, dev);
+    sis_85c49x_pci_write(0, 0xa1, 1, 0xff, dev);
+    sis_85c49x_pci_write(0, 0xc0, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xc1, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xc2, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xc3, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xc8, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xc9, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xca, 1, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xcb, 1, 0x00, dev);
 
-    sis_85c49x_pci_write(0, 0xd0, 0x79, dev);
-    sis_85c49x_pci_write(0, 0xd1, 0xff, dev);
-    sis_85c49x_pci_write(0, 0xd0, 0x78, dev);
-    sis_85c49x_pci_write(0, 0xd4, 0x00, dev);
+    sis_85c49x_pci_write(0, 0xd0, 1, 0x79, dev);
+    sis_85c49x_pci_write(0, 0xd1, 1, 0xff, dev);
+    sis_85c49x_pci_write(0, 0xd0, 1, 0x78, dev);
+    sis_85c49x_pci_write(0, 0xd4, 1, 0x00, dev);
 
     dev->pci_conf[0x67] = 0x00;
     dev->pci_conf[0xc6] = 0x00;
diff --git a/src/chipset/sis_85c50x.c b/src/chipset/sis_85c50x.c
index e932ff6ca..5eb3b518d 100644
--- a/src/chipset/sis_85c50x.c
+++ b/src/chipset/sis_85c50x.c
@@ -199,7 +199,7 @@ sis_85c50x_smm_recalc(sis_85c50x_t *dev)
 }
 
 static void
-sis_85c50x_write(int func, int addr, uint8_t val, void *priv)
+sis_85c50x_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     sis_85c50x_t *dev = (sis_85c50x_t *) priv;
 
@@ -311,7 +311,7 @@ sis_85c50x_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_85c50x_read(int func, int addr, void *priv)
+sis_85c50x_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_85c50x_t *dev = (sis_85c50x_t *) priv;
     uint8_t             ret = 0xff;
@@ -344,7 +344,7 @@ sis_85c50x_ide_recalc(sis_85c50x_t *dev)
 }
 
 static void
-sis_85c50x_sb_write(int func, int addr, uint8_t val, void *priv)
+sis_85c50x_sb_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     sis_85c50x_t *dev = (sis_85c50x_t *) priv;
 
@@ -393,7 +393,7 @@ sis_85c50x_sb_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-sis_85c50x_sb_read(int func, int addr, void *priv)
+sis_85c50x_sb_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const sis_85c50x_t *dev = (sis_85c50x_t *) priv;
     uint8_t             ret = 0xff;
@@ -553,17 +553,17 @@ sis_85c50x_reset(void *priv)
     dev->pci_conf[0x0a] = 0x00;
     dev->pci_conf[0x0b] = 0x06;
 
-    sis_85c50x_write(0, 0x51, 0x00, dev);
-    sis_85c50x_write(0, 0x53, 0x00, dev);
-    sis_85c50x_write(0, 0x54, 0x00, dev);
-    sis_85c50x_write(0, 0x55, 0x00, dev);
-    sis_85c50x_write(0, 0x56, 0x00, dev);
-    sis_85c50x_write(0, 0x5b, 0x00, dev);
-    sis_85c50x_write(0, 0x60, 0x00, dev);
-    sis_85c50x_write(0, 0x64, 0x00, dev);
-    sis_85c50x_write(0, 0x65, 0x00, dev);
-    sis_85c50x_write(0, 0x68, 0x00, dev);
-    sis_85c50x_write(0, 0x69, 0xff, dev);
+    sis_85c50x_write(0, 0x51, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x53, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x54, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x55, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x56, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x5b, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x60, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x64, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x65, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x68, 1, 0x00, dev);
+    sis_85c50x_write(0, 0x69, 1, 0xff, dev);
 
     if (dev->type & 1) {
         for (uint8_t i = 0; i < 8; i++)
@@ -586,10 +586,10 @@ sis_85c50x_reset(void *priv)
     dev->pci_conf_sb[0x0b] = 0x06;
     if (dev->type & 2)
         dev->pci_conf_sb[0x0e] = 0x80;
-    sis_85c50x_sb_write(0, 0x41, 0x80, dev);
-    sis_85c50x_sb_write(0, 0x42, 0x80, dev);
-    sis_85c50x_sb_write(0, 0x43, 0x80, dev);
-    sis_85c50x_sb_write(0, 0x44, 0x80, dev);
+    sis_85c50x_sb_write(0, 0x41, 1, 0x80, dev);
+    sis_85c50x_sb_write(0, 0x42, 1, 0x80, dev);
+    sis_85c50x_sb_write(0, 0x43, 1, 0x80, dev);
+    sis_85c50x_sb_write(0, 0x44, 1, 0x80, dev);
 
     if (dev->type & 2) {
         /* IDE (SiS 5503) */
diff --git a/src/chipset/stpc.c b/src/chipset/stpc.c
index 56eca8268..e78a68c20 100644
--- a/src/chipset/stpc.c
+++ b/src/chipset/stpc.c
@@ -213,7 +213,7 @@ stpc_localbus_read(uint16_t addr, void *priv)
 }
 
 static void
-stpc_nb_write(int func, int addr, uint8_t val, void *priv)
+stpc_nb_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     stpc_t *dev = (stpc_t *) priv;
 
@@ -260,7 +260,7 @@ stpc_nb_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-stpc_nb_read(int func, int addr, void *priv)
+stpc_nb_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const stpc_t *dev = (stpc_t *) priv;
     uint8_t       ret;
@@ -337,7 +337,7 @@ stpc_ide_bm_handlers(stpc_t *dev)
 }
 
 static void
-stpc_ide_write(int func, int addr, uint8_t val, void *priv)
+stpc_ide_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     stpc_t *dev = (stpc_t *) priv;
 
@@ -445,7 +445,7 @@ stpc_ide_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-stpc_ide_read(int func, int addr, void *priv)
+stpc_ide_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const stpc_t *dev = (stpc_t *) priv;
     uint8_t       ret;
@@ -466,12 +466,12 @@ stpc_ide_read(int func, int addr, void *priv)
 }
 
 static void
-stpc_isab_write(int func, int addr, uint8_t val, void *priv)
+stpc_isab_write(int func, int addr, int len, uint8_t val, void *priv)
 {
     stpc_t *dev = (stpc_t *) priv;
 
     if ((func == 1) && (dev->local != STPC_ATLAS)) {
-        stpc_ide_write(0, addr, val, priv);
+        stpc_ide_write(0, addr, len, val, priv);
         return;
     }
 
@@ -507,13 +507,13 @@ stpc_isab_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-stpc_isab_read(int func, int addr, void *priv)
+stpc_isab_read(int func, int addr, int len, void *priv)
 {
     const stpc_t *dev = (stpc_t *) priv;
     uint8_t       ret;
 
     if ((func == 1) && (dev->local != STPC_ATLAS))
-        ret = stpc_ide_read(0, addr, priv);
+        ret = stpc_ide_read(0, addr, len, priv);
     else if (func > 0)
         ret = 0xff;
     else
@@ -524,7 +524,7 @@ stpc_isab_read(int func, int addr, void *priv)
 }
 
 static void
-stpc_usb_write(int func, int addr, uint8_t val, void *priv)
+stpc_usb_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     stpc_t *dev = (stpc_t *) priv;
 
@@ -571,7 +571,7 @@ stpc_usb_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-stpc_usb_read(int func, int addr, void *priv)
+stpc_usb_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const stpc_t *dev = (stpc_t *) priv;
     uint8_t       ret;
diff --git a/src/chipset/umc_8886.c b/src/chipset/umc_8886.c
index 3725394c3..7350f5058 100644
--- a/src/chipset/umc_8886.c
+++ b/src/chipset/umc_8886.c
@@ -84,6 +84,7 @@
 #include <86box/machine.h>
 #include <86box/pic.h>
 #include <86box/pci.h>
+#include <86box/plat_unused.h>
 #include <86box/port_92.h>
 #include <86box/chipset.h>
 
@@ -187,7 +188,7 @@ umc_8886_irq_recalc(umc_8886_t *dev)
 }
 
 static void
-umc_8886_write(int func, int addr, uint8_t val, void *priv)
+umc_8886_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     umc_8886_t *dev = (umc_8886_t *) priv;
 
@@ -293,7 +294,7 @@ umc_8886_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-umc_8886_read(int func, int addr, void *priv)
+umc_8886_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const umc_8886_t *dev = (umc_8886_t *) priv;
     uint8_t           ret = 0xff;
diff --git a/src/chipset/umc_8890.c b/src/chipset/umc_8890.c
index cb69ce6a8..1be55de88 100644
--- a/src/chipset/umc_8890.c
+++ b/src/chipset/umc_8890.c
@@ -119,7 +119,7 @@ um8890_smram(umc_8890_t *dev)
 }
 
 static void
-um8890_write(int func, int addr, uint8_t val, void *priv)
+um8890_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     umc_8890_t *dev = (umc_8890_t *)priv;
 
@@ -158,7 +158,7 @@ um8890_write(int func, int addr, uint8_t val, void *priv)
 
 
 static uint8_t
-um8890_read(int func, int addr, void *priv)
+um8890_read(int func, int addr, UNUSED(int len), void *priv)
 {
     umc_8890_t *dev = (umc_8890_t *)priv;
     uint8_t ret = 0xff;
diff --git a/src/chipset/umc_hb4.c b/src/chipset/umc_hb4.c
index 55901b32e..ae62da166 100644
--- a/src/chipset/umc_hb4.c
+++ b/src/chipset/umc_hb4.c
@@ -275,7 +275,7 @@ hb4_smram(hb4_t *dev)
 }
 
 static void
-hb4_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+hb4_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     hb4_t *dev = (hb4_t *) priv;
 
@@ -336,7 +336,7 @@ hb4_write(UNUSED(int func), int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-hb4_read(int func, int addr, void *priv)
+hb4_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const hb4_t  *dev = (hb4_t *) priv;
     uint8_t       ret = 0xff;
diff --git a/src/chipset/via_apollo.c b/src/chipset/via_apollo.c
index 3236bbbbe..b4646ba04 100644
--- a/src/chipset/via_apollo.c
+++ b/src/chipset/via_apollo.c
@@ -29,6 +29,7 @@
 #include <86box/device.h>
 #include <86box/pci.h>
 #include <86box/chipset.h>
+#include <86box/plat_unused.h>
 #include <86box/spd.h>
 #include <86box/agpgart.h>
 
@@ -225,7 +226,7 @@ via_apollo_setup(via_apollo_t *dev)
 }
 
 static void
-via_apollo_host_bridge_write(int func, int addr, uint8_t val, void *priv)
+via_apollo_host_bridge_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     via_apollo_t *dev = (via_apollo_t *) priv;
     if (func)
@@ -684,7 +685,7 @@ via_apollo_host_bridge_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-via_apollo_read(int func, int addr, void *priv)
+via_apollo_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const via_apollo_t *dev = (via_apollo_t *) priv;
     uint8_t             ret = 0xff;
@@ -701,11 +702,11 @@ via_apollo_read(int func, int addr, void *priv)
 }
 
 static void
-via_apollo_write(int func, int addr, uint8_t val, void *priv)
+via_apollo_write(int func, int addr, int len, uint8_t val, void *priv)
 {
     switch (func) {
         case 0:
-            via_apollo_host_bridge_write(func, addr, val, priv);
+            via_apollo_host_bridge_write(func, addr, len, val, priv);
             break;
         default:
             break;
@@ -715,9 +716,9 @@ via_apollo_write(int func, int addr, uint8_t val, void *priv)
 static void
 via_apollo_reset(void *priv)
 {
-    via_apollo_write(0, 0x61, 0x00, priv);
-    via_apollo_write(0, 0x62, 0x00, priv);
-    via_apollo_write(0, 0x63, 0x00, priv);
+    via_apollo_write(0, 0x61, 1, 0x00, priv);
+    via_apollo_write(0, 0x62, 1, 0x00, priv);
+    via_apollo_write(0, 0x63, 1, 0x00, priv);
 }
 
 static void *
diff --git a/src/chipset/via_pipc.c b/src/chipset/via_pipc.c
index a476b9b99..a5883791e 100644
--- a/src/chipset/via_pipc.c
+++ b/src/chipset/via_pipc.c
@@ -170,8 +170,8 @@ pipc_log(const char *fmt, ...)
 static void    pipc_sgd_handlers(pipc_t *dev, uint8_t modem);
 static void    pipc_codec_handlers(pipc_t *dev, uint8_t modem);
 static void    pipc_sb_handlers(pipc_t *dev, uint8_t modem);
-static uint8_t pipc_read(int func, int addr, void *priv);
-static void    pipc_write(int func, int addr, uint8_t val, void *priv);
+static uint8_t pipc_read(int func, int addr, int len, void *priv);
+static void    pipc_write(int func, int addr, int len, uint8_t val, void *priv);
 
 static void
 pipc_io_trap_pact(UNUSED(int size), UNUSED(uint16_t addr), UNUSED(uint8_t write), UNUSED(uint8_t val), void *priv)
@@ -930,7 +930,7 @@ pipc_sb_get_buffer(int32_t *buffer, int len, void *priv)
 }
 
 static uint8_t
-pipc_read(int func, int addr, void *priv)
+pipc_read(int func, int addr, UNUSED(int len), void *priv)
 {
     pipc_t *dev = (pipc_t *) priv;
     uint8_t ret = 0xff;
@@ -1026,7 +1026,7 @@ pipc_ddma_update(pipc_t *dev, int addr)
 }
 
 static void
-pipc_write(int func, int addr, uint8_t val, void *priv)
+pipc_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     pipc_t *dev = (pipc_t *) priv;
     int     c;
@@ -1661,34 +1661,34 @@ pipc_reset(void *priv)
     pipc_t *dev     = (pipc_t *) priv;
     uint8_t pm_func = dev->usb[1] ? 4 : 3;
 
-    pipc_write(pm_func, 0x41, 0x00, priv);
-    pipc_write(pm_func, 0x48, 0x01, priv);
-    pipc_write(pm_func, 0x49, 0x00, priv);
+    pipc_write(pm_func, 0x41, 1, 0x00, priv);
+    pipc_write(pm_func, 0x48, 1, 0x01, priv);
+    pipc_write(pm_func, 0x49, 1, 0x00, priv);
 
     dev->power_regs[0x42] = ((dev->local >> 16) == VIA_PIPC_586) ? 0x00 : 0x50;
     acpi_set_irq_line(dev->acpi, 0x00);
 
-    pipc_write(1, 0x04, 0x80, priv);
-    pipc_write(1, 0x09, 0x85, priv);
-    pipc_write(1, 0x10, 0xf1, priv);
-    pipc_write(1, 0x11, 0x01, priv);
-    pipc_write(1, 0x14, 0xf5, priv);
-    pipc_write(1, 0x15, 0x03, priv);
-    pipc_write(1, 0x18, 0x71, priv);
-    pipc_write(1, 0x19, 0x01, priv);
-    pipc_write(1, 0x1c, 0x75, priv);
-    pipc_write(1, 0x1d, 0x03, priv);
-    pipc_write(1, 0x20, 0x01, priv);
-    pipc_write(1, 0x21, 0xcc, priv);
+    pipc_write(1, 0x04, 1, 0x80, priv);
+    pipc_write(1, 0x09, 1, 0x85, priv);
+    pipc_write(1, 0x10, 1, 0xf1, priv);
+    pipc_write(1, 0x11, 1, 0x01, priv);
+    pipc_write(1, 0x14, 1, 0xf5, priv);
+    pipc_write(1, 0x15, 1, 0x03, priv);
+    pipc_write(1, 0x18, 1, 0x71, priv);
+    pipc_write(1, 0x19, 1, 0x01, priv);
+    pipc_write(1, 0x1c, 1, 0x75, priv);
+    pipc_write(1, 0x1d, 1, 0x03, priv);
+    pipc_write(1, 0x20, 1, 0x01, priv);
+    pipc_write(1, 0x21, 1, 0xcc, priv);
     if (dev->local <= VIA_PIPC_586B)
-        pipc_write(1, 0x40, 0x04, priv);
+        pipc_write(1, 0x40, 1, 0x04, priv);
     else
-        pipc_write(1, 0x40, 0x00, priv);
+        pipc_write(1, 0x40, 1, 0x00, priv);
 
     if (dev->local < VIA_PIPC_586B)
-        pipc_write(0, 0x44, 0x00, priv);
+        pipc_write(0, 0x44, 1, 0x00, priv);
 
-    pipc_write(0, 0x77, 0x00, priv);
+    pipc_write(0, 0x77, 1, 0x00, priv);
 
     sff_set_slot(dev->bm[0], dev->pci_slot);
     sff_set_slot(dev->bm[1], dev->pci_slot);
diff --git a/src/chipset/via_vt82c505.c b/src/chipset/via_vt82c505.c
index 3daeec85b..467509fb6 100644
--- a/src/chipset/via_vt82c505.c
+++ b/src/chipset/via_vt82c505.c
@@ -38,7 +38,7 @@ typedef struct vt82c505_t {
 } vt82c505_t;
 
 static void
-vt82c505_write(int func, int addr, uint8_t val, void *priv)
+vt82c505_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     vt82c505_t   *dev = (vt82c505_t *) priv;
     uint8_t       irq;
@@ -126,7 +126,7 @@ vt82c505_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-vt82c505_read(int func, int addr, void *priv)
+vt82c505_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const vt82c505_t *dev = (vt82c505_t *) priv;
     uint8_t           ret = 0xff;
@@ -147,7 +147,7 @@ vt82c505_out(uint16_t addr, uint8_t val, void *priv)
     if (addr == 0xa8)
         dev->index = val;
     else if ((addr == 0xa9) && (dev->index >= 0x80) && (dev->index <= 0x9f))
-        vt82c505_write(0, dev->index, val, priv);
+        vt82c505_write(0, dev->index, 1, val, priv);
 }
 
 static uint8_t
@@ -157,7 +157,7 @@ vt82c505_in(uint16_t addr, void *priv)
     uint8_t           ret = 0xff;
 
     if ((addr == 0xa9) && (dev->index >= 0x80) && (dev->index <= 0x9f))
-        ret = vt82c505_read(0, dev->index, priv);
+        ret = vt82c505_read(0, dev->index, 1, priv);
 
     return ret;
 }
@@ -173,16 +173,16 @@ vt82c505_reset(void *priv)
     for (uint8_t i = 0x80; i <= 0x9f; i++) {
         switch (i) {
             case 0x81:
-                vt82c505_write(0, i, 0x01, priv);
+                vt82c505_write(0, i, 1, 0x01, priv);
                 break;
             case 0x84:
-                vt82c505_write(0, i, 0x03, priv);
+                vt82c505_write(0, i, 1, 0x03, priv);
                 break;
             case 0x93:
-                vt82c505_write(0, i, 0x40, priv);
+                vt82c505_write(0, i, 1, 0x40, priv);
                 break;
             default:
-                vt82c505_write(0, i, 0x00, priv);
+                vt82c505_write(0, i, 1, 0x00, priv);
                 break;
         }
     }
diff --git a/src/chipset/vl82c59x.c b/src/chipset/vl82c59x.c
index 69b6ebf1d..30cc63065 100644
--- a/src/chipset/vl82c59x.c
+++ b/src/chipset/vl82c59x.c
@@ -208,7 +208,7 @@ vl82c59x_set_pm_io(void *priv)
 }
 
 static void
-vl82c59x_write(int func, int addr, uint8_t val, void *priv)
+vl82c59x_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     vl82c59x_t *dev = (vl82c59x_t *) priv;
 
@@ -275,7 +275,7 @@ vl82c59x_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-vl82c59x_read(int func, int addr, void *priv)
+vl82c59x_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const vl82c59x_t *dev = (vl82c59x_t *) priv;
     uint8_t             ret = 0xff;
@@ -292,7 +292,7 @@ vl82c59x_read(int func, int addr, void *priv)
 }
 
 static void
-vl82c59x_sb_write(int func, int addr, uint8_t val, void *priv)
+vl82c59x_sb_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     vl82c59x_t *dev = (vl82c59x_t *) priv;
     uint8_t       irq;
@@ -380,7 +380,7 @@ vl82c59x_sb_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-vl82c59x_sb_read(int func, int addr, void *priv)
+vl82c59x_sb_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const vl82c59x_t *dev = (vl82c59x_t *) priv;
     uint8_t             ret = 0xff;
diff --git a/src/device/pci_bridge.c b/src/device/pci_bridge.c
index d9aeeffb6..0a323484a 100644
--- a/src/device/pci_bridge.c
+++ b/src/device/pci_bridge.c
@@ -28,6 +28,7 @@
 #include <86box/device.h>
 #include <86box/pci.h>
 #include <86box/plat_fallthrough.h>
+#include <86box/plat_unused.h>
 
 #define PCI_BRIDGE_DEC_21150   0x10110022
 #define PCI_BRIDGE_DEC_21152   0x10110024
@@ -93,7 +94,7 @@ pci_bridge_get_bus_index(void *priv)
 }
 
 static void
-pci_bridge_write(int func, int addr, uint8_t val, void *priv)
+pci_bridge_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     pci_bridge_t *dev = (pci_bridge_t *) priv;
 
@@ -391,7 +392,7 @@ pci_bridge_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-pci_bridge_read(int func, int addr, void *priv)
+pci_bridge_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const pci_bridge_t *dev = (pci_bridge_t *) priv;
     uint8_t             ret;
diff --git a/src/device/vfio.c b/src/device/vfio.c
index 2217eb509..776ded002 100644
--- a/src/device/vfio.c
+++ b/src/device/vfio.c
@@ -246,12 +246,12 @@ vfio_log(const char *fmt, ...)
 #endif
 
 static uint8_t  vfio_bar_gettype(vfio_device_t *dev, vfio_region_t *bar);
-static uint8_t  vfio_config_readb(int func, int addr, void *priv);
-static uint16_t vfio_config_readw(int func, int addr, void *priv);
-static uint32_t vfio_config_readl(int func, int addr, void *priv);
-static void     vfio_config_writeb(int func, int addr, uint8_t val, void *priv);
-static void     vfio_config_writew(int func, int addr, uint16_t val, void *priv);
-static void     vfio_config_writel(int func, int addr, uint32_t val, void *priv);
+static uint8_t  vfio_config_readb(int func, int addr, int len, void *priv);
+static uint16_t vfio_config_readw(int func, int addr, int len, void *priv);
+static uint32_t vfio_config_readl(int func, int addr, int len, void *priv);
+static void     vfio_config_writeb(int func, int addr, int len, uint8_t val, void *priv);
+static void     vfio_config_writew(int func, int addr, int len, uint16_t val, void *priv);
+static void     vfio_config_writel(int func, int addr, int len, uint32_t val, void *priv);
 static void     vfio_irq_intx_setpin(vfio_device_t *dev);
 static void     vfio_irq_msi_disable(vfio_device_t *dev);
 static void     vfio_irq_msix_disable(vfio_device_t *dev);
@@ -371,7 +371,7 @@ vfio_quirk_configmirror_readb(uint32_t addr, void *priv)
     vfio_mem_readb_fd(addr, bar);
 
     /* Read configuration register. */
-    uint8_t ret = vfio_config_readb(0, addr - bar->quirks.configmirror.offset, dev);
+    uint8_t ret = vfio_config_readb(0, addr - bar->quirks.configmirror.offset, 1, dev);
     vfio_log_op("VFIO %s: Config mirror: Read %02X from index %02X\n",
                 dev->name, ret, addr - bar->quirks.configmirror.offset);
 
@@ -388,7 +388,7 @@ vfio_quirk_configmirror_readw(uint32_t addr, void *priv)
     vfio_mem_readw_fd(addr, bar);
 
     /* Read configuration register. */
-    uint16_t ret = vfio_config_readw(0, addr - bar->quirks.configmirror.offset, dev);
+    uint16_t ret = vfio_config_readw(0, addr - bar->quirks.configmirror.offset, 2, dev);
     vfio_log_op("VFIO %s: Config mirror: Read %04X from index %02X\n",
                 dev->name, ret, addr - bar->quirks.configmirror.offset);
 
@@ -405,7 +405,7 @@ vfio_quirk_configmirror_readl(uint32_t addr, void *priv)
     vfio_mem_readl_fd(addr, bar);
 
     /* Read configuration register. */
-    uint32_t ret = vfio_config_readl(0, addr - bar->quirks.configmirror.offset, dev);
+    uint32_t ret = vfio_config_readl(0, addr - bar->quirks.configmirror.offset, 4, dev);
     vfio_log_op("VFIO %s: Config mirror: Read %08X from index %02X\n",
                 dev->name, ret, addr - bar->quirks.configmirror.offset);
 
@@ -421,7 +421,7 @@ vfio_quirk_configmirror_writeb(uint32_t addr, uint8_t val, void *priv)
     /* Write configuration register. */
     vfio_log_op("VFIO %s: Config mirror: Write %02X to index %02X\n",
                 dev->name, val, addr - bar->quirks.configmirror.offset);
-    vfio_config_writeb(0, addr - bar->quirks.configmirror.offset, val, dev);
+    vfio_config_writeb(0, addr - bar->quirks.configmirror.offset, 1, val, dev);
 }
 
 static void
@@ -433,7 +433,7 @@ vfio_quirk_configmirror_writew(uint32_t addr, uint16_t val, void *priv)
     /* Write configuration register. */
     vfio_log_op("VFIO %s: Config mirror: Write %04X to index %02X\n",
                 dev->name, val, addr - bar->quirks.configmirror.offset);
-    vfio_config_writew(0, addr - bar->quirks.configmirror.offset, val, dev);
+    vfio_config_writew(0, addr - bar->quirks.configmirror.offset, 2, val, dev);
 }
 
 static void
@@ -445,7 +445,7 @@ vfio_quirk_configmirror_writel(uint32_t addr, uint32_t val, void *priv)
     /* Write configuration register. */
     vfio_log_op("VFIO %s: Config mirror: Write %08X to index %02X\n",
                 dev->name, val, addr - bar->quirks.configmirror.offset);
-    vfio_config_writel(0, addr - bar->quirks.configmirror.offset, val, dev);
+    vfio_config_writel(0, addr - bar->quirks.configmirror.offset, 4, val, dev);
 }
 
 static void
@@ -541,11 +541,11 @@ vfio_quirk_configwindow_data_readb(uint16_t addr, void *priv)
     /* Read configuration register if part of the main PCI configuration space. */
     uint32_t index = bar->quirks.configwindow.index;
     if ((index >= bar->quirks.configwindow.offset[0].start) && (index <= bar->quirks.configwindow.offset[0].end)) {
-        ret = vfio_config_readb(0, index - bar->quirks.configwindow.offset[0].start, dev);
+        ret = vfio_config_readb(0, index - bar->quirks.configwindow.offset[0].start, 1, dev);
         vfio_log_op("VFIO %s: Config window: Read %02X from primary index %08X\n",
                     dev->name, ret, index);
     } else if ((index >= bar->quirks.configwindow.offset[1].start) && (index <= bar->quirks.configwindow.offset[1].end)) {
-        ret = vfio_config_readb(0, index - bar->quirks.configwindow.offset[1].start, dev);
+        ret = vfio_config_readb(0, index - bar->quirks.configwindow.offset[1].start, 1, dev);
         vfio_log_op("VFIO %s: Config window: Read %02X from secondary index %08X\n",
                     dev->name, ret, index);
     }
@@ -565,11 +565,11 @@ vfio_quirk_configwindow_data_readw(uint16_t addr, void *priv)
     /* Read configuration register if part of the main PCI configuration space. */
     uint32_t index = bar->quirks.configwindow.index;
     if ((index >= bar->quirks.configwindow.offset[0].start) && (index <= bar->quirks.configwindow.offset[0].end)) {
-        ret = vfio_config_readw(0, index - bar->quirks.configwindow.offset[0].start, dev);
+        ret = vfio_config_readw(0, index - bar->quirks.configwindow.offset[0].start, 2, dev);
         vfio_log_op("VFIO %s: Config window: Read %04X from primary index %08X\n",
                     dev->name, ret, index);
     } else if ((index >= bar->quirks.configwindow.offset[1].start) && (index <= bar->quirks.configwindow.offset[1].end)) {
-        ret = vfio_config_readw(0, index - bar->quirks.configwindow.offset[1].start, dev);
+        ret = vfio_config_readw(0, index - bar->quirks.configwindow.offset[1].start, 2, dev);
         vfio_log_op("VFIO %s: Config window: Read %04X from secondary index %08X\n",
                     dev->name, ret, index);
     }
@@ -589,11 +589,11 @@ vfio_quirk_configwindow_data_readl(uint16_t addr, void *priv)
     /* Read configuration register if part of the main PCI configuration space. */
     uint32_t index = bar->quirks.configwindow.index;
     if ((index >= bar->quirks.configwindow.offset[0].start) && (index <= bar->quirks.configwindow.offset[0].end)) {
-        ret = vfio_config_readl(0, index - bar->quirks.configwindow.offset[0].start, dev);
+        ret = vfio_config_readl(0, index - bar->quirks.configwindow.offset[0].start, 4, dev);
         vfio_log_op("VFIO %s: Config window: Read %08X from primary index %08X\n",
                     dev->name, ret, index);
     } else if ((index >= bar->quirks.configwindow.offset[1].start) && (index <= bar->quirks.configwindow.offset[1].end)) {
-        ret = vfio_config_readl(0, index - bar->quirks.configwindow.offset[1].start, dev);
+        ret = vfio_config_readl(0, index - bar->quirks.configwindow.offset[1].start, 4, dev);
         vfio_log_op("VFIO %s: Config window: Read %08X from secondary index %08X\n",
                     dev->name, ret, index);
     }
@@ -612,12 +612,12 @@ vfio_quirk_configwindow_data_writeb(uint16_t addr, uint8_t val, void *priv)
     if ((index >= bar->quirks.configwindow.offset[0].start) && (index <= bar->quirks.configwindow.offset[0].end)) {
         vfio_log_op("VFIO %s: Config window: Write %02X to primary index %08X\n",
                     dev->name, val, index);
-        vfio_config_writeb(0, index - bar->quirks.configwindow.offset[0].start, val, dev);
+        vfio_config_writeb(0, index - bar->quirks.configwindow.offset[0].start, 1, val, dev);
         return;
     } else if ((index >= bar->quirks.configwindow.offset[1].start) && (index <= bar->quirks.configwindow.offset[1].end)) {
         vfio_log_op("VFIO %s: Config window: Write %02X to secondary index %08X\n",
                     dev->name, val, index);
-        vfio_config_writeb(0, index - bar->quirks.configwindow.offset[1].start, val, dev);
+        vfio_config_writeb(0, index - bar->quirks.configwindow.offset[1].start, 1, val, dev);
         return;
     }
 
@@ -636,12 +636,12 @@ vfio_quirk_configwindow_data_writew(uint16_t addr, uint16_t val, void *priv)
     if ((index >= bar->quirks.configwindow.offset[0].start) && (index <= bar->quirks.configwindow.offset[0].end)) {
         vfio_log_op("VFIO %s: Config window: Write %04X to primary index %08X\n",
                     dev->name, val, index);
-        vfio_config_writew(0, index - bar->quirks.configwindow.offset[0].start, val, dev);
+        vfio_config_writew(0, index - bar->quirks.configwindow.offset[0].start, 2, val, dev);
         return;
     } else if ((index >= bar->quirks.configwindow.offset[1].start) && (index <= bar->quirks.configwindow.offset[1].end)) {
         vfio_log_op("VFIO %s: Config window: Write %04X to secondary index %08X\n",
                     dev->name, val, index);
-        vfio_config_writew(0, index - bar->quirks.configwindow.offset[1].start, val, dev);
+        vfio_config_writew(0, index - bar->quirks.configwindow.offset[1].start, 2, val, dev);
         return;
     }
 
@@ -660,12 +660,12 @@ vfio_quirk_configwindow_data_writel(uint16_t addr, uint32_t val, void *priv)
     if ((index >= bar->quirks.configwindow.offset[0].start) && (index <= bar->quirks.configwindow.offset[0].end)) {
         vfio_log_op("VFIO %s: Config window: Write %08X to primary index %08X\n",
                     dev->name, val, index);
-        vfio_config_writel(0, index - bar->quirks.configwindow.offset[0].start, val, dev);
+        vfio_config_writel(0, index - bar->quirks.configwindow.offset[0].start, 4, val, dev);
         return;
     } else if ((index >= bar->quirks.configwindow.offset[1].start) && (index <= bar->quirks.configwindow.offset[1].end)) {
         vfio_log_op("VFIO %s: Config window: Write %08X to secondary index %08X\n",
                     dev->name, val, index);
-        vfio_config_writel(0, index - bar->quirks.configwindow.offset[1].start, val, dev);
+        vfio_config_writel(0, index - bar->quirks.configwindow.offset[1].start, 4, val, dev);
         return;
     }
 
@@ -1037,7 +1037,7 @@ vfio_quirk_nvidia3d0_data_readb(uint16_t addr, void *priv)
 
     /* Read configuration register if part of the main PCI configuration space. */
     if ((prev_state == NVIDIA_3D0_READ) && (((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00001800) || ((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00088000))) {
-        ret = vfio_config_readb(0, dev->quirks.nvidia3d0.index, dev);
+        ret = vfio_config_readb(0, dev->quirks.nvidia3d0.index, 1, dev);
         vfio_log_op("VFIO %s: NVIDIA 3D0: Read %02X from index %08X\n", dev->name,
                     ret, dev->quirks.nvidia3d0.index);
     }
@@ -1057,7 +1057,7 @@ vfio_quirk_nvidia3d0_data_readw(uint16_t addr, void *priv)
 
     /* Read configuration register if part of the main PCI configuration space. */
     if ((prev_state == NVIDIA_3D0_READ) && (((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00001800) || ((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00088000))) {
-        ret = vfio_config_readw(0, dev->quirks.nvidia3d0.index, dev);
+        ret = vfio_config_readw(0, dev->quirks.nvidia3d0.index, 2, dev);
         vfio_log_op("VFIO %s: NVIDIA 3D0: Read %04X from index %08X\n", dev->name,
                     ret, dev->quirks.nvidia3d0.index);
     }
@@ -1077,7 +1077,7 @@ vfio_quirk_nvidia3d0_data_readl(uint16_t addr, void *priv)
 
     /* Read configuration register if part of the main PCI configuration space. */
     if ((prev_state == NVIDIA_3D0_READ) && (((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00001800) || ((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00088000))) {
-        ret = vfio_config_readl(0, dev->quirks.nvidia3d0.index, dev);
+        ret = vfio_config_readl(0, dev->quirks.nvidia3d0.index, 4, dev);
         vfio_log_op("VFIO %s: NVIDIA 3D0: Read %08X from index %08X\n", dev->name,
                     ret, dev->quirks.nvidia3d0.index);
     }
@@ -1104,7 +1104,7 @@ vfio_quirk_nvidia3d0_data_writeb(uint16_t addr, uint8_t val, void *priv)
             /* Write configuration register. */
             vfio_log_op("VFIO %s: NVIDIA 3D0: Write %02X to index %08X\n", dev->name,
                         val, dev->quirks.nvidia3d0.index);
-            vfio_config_writeb(0, dev->quirks.nvidia3d0.index, val, dev);
+            vfio_config_writeb(0, dev->quirks.nvidia3d0.index, val, 1, dev);
             return;
         }
     }
@@ -1131,7 +1131,7 @@ vfio_quirk_nvidia3d0_data_writew(uint16_t addr, uint16_t val, void *priv)
         if (((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00001800) || ((dev->quirks.nvidia3d0.index & 0xffffff00) == 0x00088000)) {
             vfio_log_op("VFIO %s: NVIDIA 3D0: Write %04X to index %08X\n", dev->name,
                         val, dev->quirks.nvidia3d0.index);
-            vfio_config_writew(0, dev->quirks.nvidia3d0.index, val, dev);
+            vfio_config_writew(0, dev->quirks.nvidia3d0.index, val, 2, dev);
             return;
         }
     }
@@ -1159,7 +1159,7 @@ vfio_quirk_nvidia3d0_data_writel(uint16_t addr, uint32_t val, void *priv)
             /* Write configuration register. */
             vfio_log_op("VFIO %s: NVIDIA 3D0: Write %08X to index %08X\n", dev->name,
                         val, dev->quirks.nvidia3d0.index);
-            vfio_config_writel(0, dev->quirks.nvidia3d0.index, val, dev);
+            vfio_config_writel(0, dev->quirks.nvidia3d0.index, val, 4, dev);
             return;
         }
     }
@@ -1198,7 +1198,7 @@ vfio_quirk_remap(vfio_device_t *dev, vfio_region_t *bar, uint8_t enable)
             /* BAR 2 configuration space mirror, and BAR 1/4 configuration space window. */
             if (j && !i) {
                 /* QEMU only enables the mirror here if BAR 2 is 64-bit capable. */
-                if ((bar->bar_id == 2) && ((vfio_config_readb(0, 0x18, dev) & 0x07) == 0x04))
+                if ((bar->bar_id == 2) && ((vfio_config_readb(0, 0x18, 1, dev) & 0x07) == 0x04))
                     vfio_quirk_configmirror(dev, bar, 0x4000, 0, enable);
                 else if (bar->bar_id == 4)
                     vfio_quirk_configwindow(dev, bar, 0x00, 4, 0x04, 4, 0x4000, 0x4000, enable);
@@ -1479,7 +1479,7 @@ ceilpow2(uint32_t size)
 }
 
 static uint8_t
-vfio_config_readb(int func, int addr, void *priv)
+vfio_config_readb(int func, int addr, UNUSED(int len), void *priv)
 {
     vfio_device_t *dev = (vfio_device_t *) priv;
     if (func)
@@ -1602,19 +1602,19 @@ end:
 }
 
 static uint16_t
-vfio_config_readw(int func, int addr, void *priv)
+vfio_config_readw(int func, int addr, UNUSED(int len), void *priv)
 {
-    return vfio_config_readb(func, addr, priv) | (vfio_config_readb(func, addr + 1, priv) << 8);
+    return vfio_config_readb(func, addr, 2, priv) | (vfio_config_readb(func, addr + 1, 2, priv) << 8);
 }
 
 static uint32_t
-vfio_config_readl(int func, int addr, void *priv)
+vfio_config_readl(int func, int addr, UNUSED(int len), void *priv)
 {
-    return vfio_config_readb(func, addr, priv) | (vfio_config_readb(func, addr + 1, priv) << 8) | (vfio_config_readb(func, addr + 2, priv) << 16) | (vfio_config_readb(func, addr + 3, priv) << 24);
+    return vfio_config_readb(func, addr, 4, priv) | (vfio_config_readb(func, addr + 1, 4, priv) << 8) | (vfio_config_readb(func, addr + 2, 4, priv) << 16) | (vfio_config_readb(func, addr + 3, 4, priv) << 24);
 }
 
 static void
-vfio_config_writeb(int func, int addr, uint8_t val, void *priv)
+vfio_config_writeb(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     vfio_device_t *dev = (vfio_device_t *) priv;
     if (func)
@@ -1850,19 +1850,19 @@ end:
 }
 
 static void
-vfio_config_writew(int func, int addr, uint16_t val, void *priv)
+vfio_config_writew(int func, int addr, UNUSED(int len), uint16_t val, void *priv)
 {
-    vfio_config_writeb(func, addr, val, priv);
-    vfio_config_writeb(func, addr | 1, val >> 8, priv);
+    vfio_config_writeb(func, addr, 2, val, priv);
+    vfio_config_writeb(func, addr | 1, 2, val >> 8, priv);
 }
 
 static void
-vfio_config_writel(int func, int addr, uint32_t val, void *priv)
+vfio_config_writel(int func, int addr, UNUSED(int len), uint32_t val, void *priv)
 {
-    vfio_config_writeb(func, addr, val, priv);
-    vfio_config_writeb(func, addr | 1, val >> 8, priv);
-    vfio_config_writeb(func, addr | 2, val >> 16, priv);
-    vfio_config_writeb(func, addr | 3, val >> 24, priv);
+    vfio_config_writeb(func, addr, 4, val, priv);
+    vfio_config_writeb(func, addr | 1, 4, val >> 8, priv);
+    vfio_config_writeb(func, addr | 2, 4, val >> 16, priv);
+    vfio_config_writeb(func, addr | 3, 4, val >> 24, priv);
 }
 
 static void
@@ -2549,13 +2549,13 @@ vfio_dev_prereset(vfio_device_t *dev)
     /* Extra steps for devices with power management capability. */
     if (dev->pm_cap) {
         /* Make sure the device is in D0 state. */
-        uint8_t pm_ctrl = vfio_config_readb(0, dev->pm_cap + 4, dev),
+        uint8_t pm_ctrl = vfio_config_readb(0, dev->pm_cap + 4, 1, dev),
                 state   = pm_ctrl & 0x03;
         if (state) {
             pm_ctrl &= ~0x03;
-            vfio_config_writeb(0, dev->pm_cap + 4, pm_ctrl, dev);
+            vfio_config_writeb(0, dev->pm_cap + 4, pm_ctrl, 1, dev);
 
-            pm_ctrl = vfio_config_readb(0, dev->pm_cap + 4, dev);
+            pm_ctrl = vfio_config_readb(0, dev->pm_cap + 4, 1, dev);
             state   = pm_ctrl & 0x03;
             if (state)
                 vfio_log("VFIO %s: Device stuck in D%d state\n", dev->name, state);
@@ -2566,10 +2566,10 @@ vfio_dev_prereset(vfio_device_t *dev)
     }
 
     /* Enable function-level reset if supported. */
-    dev->can_flr_reset = (dev->pcie_cap && (vfio_config_readb(0, dev->pcie_cap + 7, dev) & 0x10)) || (dev->af_cap && (vfio_config_readb(0, dev->af_cap + 3, dev) & 0x02));
+    dev->can_flr_reset = (dev->pcie_cap && (vfio_config_readb(0, dev->pcie_cap + 7, 1, dev) & 0x10)) || (dev->af_cap && (vfio_config_readb(0, dev->af_cap + 3, 1, dev) & 0x02));
 
     /* Disable bus master, BARs, expansion ROM and VGA regions; also enable INTx. */
-    vfio_config_writew(0, 0x04, vfio_config_readw(0, 0x04, dev) & ~0x0407, dev);
+    vfio_config_writew(0, 0x04, vfio_config_readw(0, 0x04, 2, dev) & ~0x0407, dev);
 }
 
 static void
diff --git a/src/disk/hdc_ide_cmd640.c b/src/disk/hdc_ide_cmd640.c
index ea2a195d9..44e488df4 100644
--- a/src/disk/hdc_ide_cmd640.c
+++ b/src/disk/hdc_ide_cmd640.c
@@ -30,6 +30,7 @@
 #include <86box/mem.h>
 #include <86box/pci.h>
 #include <86box/pic.h>
+#include <86box/plat_unused.h>
 #include <86box/timer.h>
 #include <86box/hdc.h>
 #include <86box/hdc_ide.h>
@@ -289,7 +290,7 @@ cmd640_vlb_readl(uint16_t addr, void *priv)
 }
 
 static void
-cmd640_pci_write(int func, int addr, uint8_t val, void *priv)
+cmd640_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     cmd640_t *dev = (cmd640_t *) priv;
 
@@ -367,7 +368,7 @@ cmd640_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-cmd640_pci_read(int func, int addr, void *priv)
+cmd640_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     cmd640_t *dev = (cmd640_t *) priv;
     uint8_t   ret = 0xff;
diff --git a/src/disk/hdc_ide_cmd646.c b/src/disk/hdc_ide_cmd646.c
index 333cd5e30..9cd50e871 100644
--- a/src/disk/hdc_ide_cmd646.c
+++ b/src/disk/hdc_ide_cmd646.c
@@ -30,6 +30,7 @@
 #include <86box/mem.h>
 #include <86box/pci.h>
 #include <86box/pic.h>
+#include <86box/plat_unused.h>
 #include <86box/timer.h>
 #include <86box/hdc.h>
 #include <86box/hdc_ide.h>
@@ -296,7 +297,7 @@ cmd646_bios_handler(cmd646_t *dev)
 }
 
 static void
-cmd646_pci_write(int func, int addr, uint8_t val, void *priv)
+cmd646_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     cmd646_t *dev         = (cmd646_t *) priv;
     int       reg50       = dev->regs[0x50];
@@ -481,7 +482,7 @@ cmd646_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-cmd646_pci_read(int func, int addr, void *priv)
+cmd646_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     cmd646_t *dev         = (cmd646_t *) priv;
     uint8_t   ret         = 0xff;
diff --git a/src/disk/hdc_ide_rz1000.c b/src/disk/hdc_ide_rz1000.c
index 56568cc2c..7559041b8 100644
--- a/src/disk/hdc_ide_rz1000.c
+++ b/src/disk/hdc_ide_rz1000.c
@@ -30,6 +30,7 @@
 #include <86box/mem.h>
 #include <86box/pci.h>
 #include <86box/pic.h>
+#include <86box/plat_unused.h>
 #include <86box/timer.h>
 #include <86box/hdc.h>
 #include <86box/hdc_ide.h>
@@ -108,7 +109,7 @@ rz1000_ide_handlers(rz1000_t *dev)
 }
 
 static void
-rz1000_pci_write(int func, int addr, uint8_t val, void *priv)
+rz1000_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     rz1000_t *dev = (rz1000_t *) priv;
 
@@ -138,7 +139,7 @@ rz1000_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-rz1000_pci_read(int func, int addr, void *priv)
+rz1000_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     rz1000_t *dev = (rz1000_t *) priv;
     uint8_t   ret = 0xff;
diff --git a/src/disk/hdc_ide_w83769f.c b/src/disk/hdc_ide_w83769f.c
index 25ee16d10..cb4d91778 100644
--- a/src/disk/hdc_ide_w83769f.c
+++ b/src/disk/hdc_ide_w83769f.c
@@ -30,6 +30,7 @@
 #include <86box/mem.h>
 #include <86box/pci.h>
 #include <86box/pic.h>
+#include <86box/plat_unused.h>
 #include <86box/timer.h>
 #include <86box/hdc.h>
 #include <86box/hdc_ide.h>
@@ -233,7 +234,7 @@ w83769f_vlb_readl(uint16_t addr, void *priv)
 }
 
 static void
-w83769f_pci_write(int func, int addr, uint8_t val, void *priv)
+w83769f_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     w83769f_t *dev = (w83769f_t *) priv;
 
@@ -252,7 +253,7 @@ w83769f_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-w83769f_pci_read(int func, int addr, void *priv)
+w83769f_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     w83769f_t *dev = (w83769f_t *) priv;
     uint8_t    ret = 0xff;
diff --git a/src/include/86box/pci.h b/src/include/86box/pci.h
index a721db005..f5f5aee04 100644
--- a/src/include/86box/pci.h
+++ b/src/include/86box/pci.h
@@ -266,12 +266,12 @@ extern void        pci_remap_bus(uint8_t bus_index, uint8_t bus_number);
 extern void        pci_register_bus_slot(int bus, int card, int type, int inta, int intb, int intc, int intd);
 
 /* Add a PCI card. */
-extern void        pci_add_card(uint8_t add_type, uint8_t (*read)(int func, int addr, void *priv),
-                                void (*write)(int func, int addr, uint8_t val, void *priv), void *priv, uint8_t *slot);
+extern void        pci_add_card(uint8_t add_type, uint8_t (*read)(int func, int addr, int len, void *priv),
+                                void (*write)(int func, int addr, int len, uint8_t val, void *priv), void *priv, uint8_t *slot);
 
 /* Add an instance of the PCI bridge. */
-extern void        pci_add_bridge(uint8_t agp, uint8_t (*read)(int func, int addr, void *priv),
-                                  void (*write)(int func, int addr, uint8_t val, void *priv), void *priv,
+extern void        pci_add_bridge(uint8_t agp, uint8_t (*read)(int func, int addr, int len, void *priv),
+                                  void (*write)(int func, int addr, int len, uint8_t val, void *priv), void *priv,
                                   uint8_t *slot);
 
 /* Register the cards that have been added into slots. */
diff --git a/src/network/net_ne2000.c b/src/network/net_ne2000.c
index 3e2e7dd38..decb23d02 100644
--- a/src/network/net_ne2000.c
+++ b/src/network/net_ne2000.c
@@ -799,7 +799,7 @@ nic_update_bios(nic_t *dev)
 }
 
 static uint8_t
-nic_pci_read(UNUSED(int func), int addr, void *priv)
+nic_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const nic_t  *dev = (nic_t *) priv;
     uint8_t       ret = 0x00;
@@ -894,7 +894,7 @@ nic_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-nic_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+nic_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     nic_t  *dev = (nic_t *) priv;
     uint8_t valxor;
diff --git a/src/network/net_pcnet.c b/src/network/net_pcnet.c
index 2d9aa88bb..e4cad2552 100644
--- a/src/network/net_pcnet.c
+++ b/src/network/net_pcnet.c
@@ -2588,7 +2588,7 @@ pcnet_ioset(nic_t *dev, uint16_t addr, int len)
 }
 
 static void
-pcnet_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+pcnet_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     nic_t  *dev = (nic_t *) priv;
     uint8_t valxor;
@@ -2671,7 +2671,7 @@ pcnet_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
 }
 
 static uint8_t
-pcnet_pci_read(UNUSED(int func), int addr, void *priv)
+pcnet_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const nic_t *dev = (nic_t *) priv;
 
diff --git a/src/network/net_rtl8139.c b/src/network/net_rtl8139.c
index 9cc52417f..5c50f088c 100644
--- a/src/network/net_rtl8139.c
+++ b/src/network/net_rtl8139.c
@@ -3100,7 +3100,7 @@ rtl8139_timer(void *priv)
 }
 
 static uint8_t
-rtl8139_pci_read(UNUSED(int func), int addr, void *priv)
+rtl8139_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const RTL8139State *s = (RTL8139State *) priv;
 
@@ -3157,7 +3157,7 @@ rtl8139_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-rtl8139_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+rtl8139_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     RTL8139State *s = (RTL8139State *) priv;
 
diff --git a/src/network/net_tulip.c b/src/network/net_tulip.c
index 3f1825a1e..e95810cfa 100644
--- a/src/network/net_tulip.c
+++ b/src/network/net_tulip.c
@@ -1182,7 +1182,7 @@ tulip_srom_crc(uint8_t *eeprom)
 }
 
 static uint8_t
-tulip_pci_read(UNUSED(int func), int addr, void *priv)
+tulip_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const TULIPState *s = (TULIPState *) priv;
     uint8_t ret = 0;
@@ -1301,7 +1301,7 @@ tulip_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-tulip_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+tulip_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     TULIPState *s = (TULIPState *) priv;
 
diff --git a/src/pci.c b/src/pci.c
index 16e8cdb4f..9d08a9e08 100644
--- a/src/pci.c
+++ b/src/pci.c
@@ -40,15 +40,15 @@ typedef struct pci_card_t {
     uint8_t     irq_routing[PCI_INT_PINS_NUM];
 
     void *      priv;
-    void        (*write)(int func, int addr, uint8_t val, void *priv);
-    uint8_t     (*read)(int func, int addr, void *priv);
+    void        (*write)(int func, int addr, int len, uint8_t val, void *priv);
+    uint8_t     (*read)(int func, int addr, int len, void *priv);
 } pci_card_t;
 
 typedef struct pci_card_desc_t {
     uint8_t     type;
     void *      priv;
-    void        (*write)(int func, int addr, uint8_t val, void *priv);
-    uint8_t     (*read)(int func, int addr, void *priv);
+    void        (*write)(int func, int addr, int len, uint8_t val, void *priv);
+    uint8_t     (*read)(int func, int addr, int len, void *priv);
     uint8_t     *slot;
 } pci_card_desc_t;
 
@@ -91,6 +91,7 @@ static int         pci_card;
 static int         pci_bus;
 static int         pci_key;
 static int         pci_trc_reg = 0;
+static int         pci_access_len = 0;
 static uint32_t    pci_enable = 0x00000000;
 
 static void        pci_reset_regs(void);
@@ -174,7 +175,7 @@ pci_irq(uint8_t slot, uint8_t pci_int, int level, int set, uint8_t *irq_state)
                 return;
 
             if (pci_flags & FLAG_NO_IRQ_STEERING)
-                irq_line = pci_cards[slot].read(0, 0x3c, pci_cards[slot].priv);
+                irq_line = pci_cards[slot].read(0, 0x3c, 1, pci_cards[slot].priv);
             else {
                 irq_routing = pci_cards[slot].irq_routing[pci_int_index];
 
@@ -349,12 +350,12 @@ pci_reg_write(uint16_t port, uint8_t val)
     slot = pci_card_to_slot_mapping[pci_bus_number_to_index_mapping[pci_bus]][pci_card];
     if (slot != PCI_CARD_INVALID) {
         if (pci_cards[slot].write)
-            pci_cards[slot].write(pci_func, pci_index | (port & 0x03), val, pci_cards[slot].priv);
+            pci_cards[slot].write(pci_func, pci_index | (port & 0x03), pci_access_len, val, pci_cards[slot].priv);
     }
-    pci_log("PCI: [WB] Mechanism #%i, slot %02X, %s card %02X:%02X, function %02X, index %02X = %02X\n",
+    pci_log("PCI: [WB] Mechanism #%i, slot %02X, %s card %02X:%02X, function %02X, index %02X, length %I = %02X\n",
             (port >= 0xc000) ? 2 : 1, slot,
             (slot == PCI_CARD_INVALID) ? "non-existent" : (pci_cards[slot].write ? "used" : "unused"),
-            pci_card, pci_bus, pci_func, pci_index | (port & 0x03), val);
+            pci_card, pci_bus, pci_func, pci_index | (port & 0x03), pci_access_len, val);
 }
 
 static void
@@ -364,6 +365,8 @@ pci_reset_regs(void)
     pci_enable = 0x00000000;
 
     pci_flags &= ~(FLAG_CONFIG_IO_ON | FLAG_CONFIG_M1_IO_ON);
+
+    pci_access_len = 1;
 }
 
 void
@@ -496,16 +499,24 @@ pci_writew(uint16_t port, uint16_t val, UNUSED(void *priv))
 {
     if (port & 0x0001) {
         /* Non-aligned access, split into two byte accesses. */
+        if (pci_access_len == 1)
+            pci_access_len = 2;
         pci_write(port, val & 0xff, priv);
         pci_write(port + 1, val >> 8, priv);
+        if (pci_access_len == 2)
+            pci_access_len = 1;
     } else {
         /* Aligned access, still split because we cheat. */
         switch (port) {
             case 0xcfc:
             case 0xcfe:
             case 0xc000 ... 0xcffe:
+                if (pci_access_len == 1)
+                    pci_access_len = 2;
                 pci_write(port, val & 0xff, priv);
                 pci_write(port + 1, val >> 8, priv);
+                if (pci_access_len == 2)
+                    pci_access_len = 1;
                 break;
 
             default:
@@ -519,8 +530,10 @@ pci_writel(uint16_t port, uint32_t val, UNUSED(void *priv))
 {
     if (port & 0x0003) {
         /* Non-aligned access, split into two word accesses. */
+        pci_access_len = 4;
         pci_writew(port, val & 0xffff, priv);
         pci_writew(port + 2, val >> 16, priv);
+        pci_access_len = 1;
     } else {
         /* Aligned access. */
         switch (port) {
@@ -545,8 +558,10 @@ pci_writel(uint16_t port, uint32_t val, UNUSED(void *priv))
             case 0xcfc:
             case 0xc000 ... 0xcffc:
                 /* Still split because we cheat. */
+                pci_access_len = 4;
                 pci_writew(port, val & 0xffff, priv);
                 pci_writew(port + 2, val >> 16, priv);
+                pci_access_len = 1;
                 break;
 
             default:
@@ -569,12 +584,12 @@ pci_reg_read(uint16_t port)
     slot = pci_card_to_slot_mapping[pci_bus_number_to_index_mapping[pci_bus]][pci_card];
     if (slot != PCI_CARD_INVALID) {
         if (pci_cards[slot].read)
-            ret = pci_cards[slot].read(pci_func, pci_index | (port & 0x03), pci_cards[slot].priv);
+            ret = pci_cards[slot].read(pci_func, pci_index | (port & 0x03), pci_access_len, pci_cards[slot].priv);
     }
-    pci_log("PCI: [RB] Mechanism #%i, slot %02X, %s card %02X:%02X, function %02X, index %02X = %02X\n",
+    pci_log("PCI: [RB] Mechanism #%i, slot %02X, %s card %02X:%02X, function %02X, index %02X, length %i = %02X\n",
             (port >= 0xc000) ? 2 : 1, slot,
             (slot == PCI_CARD_INVALID) ? "non-existent" : (pci_cards[slot].read ? "used" : "unused"),
-            pci_card, pci_bus, pci_func, pci_index | (port & 0x03), ret);
+            pci_card, pci_bus, pci_access_len, pci_index | (port & 0x03), pci_func, ret);
 
     return ret;
 }
@@ -643,8 +658,12 @@ pci_readw(uint16_t port, UNUSED(void *priv))
             case 0xcfc:
             case 0xcfe:
             case 0xc000 ... 0xcffe:
+                if (pci_access_len == 1)
+                    pci_access_len = 2;
                 ret = pci_read(port, priv);
                 ret |= ((uint16_t) pci_read(port + 1, priv)) << 8;
+                if (pci_access_len == 2)
+                    pci_access_len = 1;
                 break;
 
             default:
@@ -662,8 +681,10 @@ pci_readl(uint16_t port, UNUSED(void *priv))
 
     if (port & 0x0003) {
         /* Non-aligned access, split into two word accesses. */
+        pci_access_len = 4;
         ret = pci_readw(port, priv);
         ret |= ((uint32_t) pci_readw(port + 2, priv)) << 16;
+        pci_access_len = 1;
     } else {
         /* Aligned access. */
         switch (port) {
@@ -682,8 +703,10 @@ pci_readl(uint16_t port, UNUSED(void *priv))
             case 0xcfc:
             case 0xc000 ... 0xcffc:
                 /* Still split because we cheat. */
+                pci_access_len = 4;
                 ret = pci_readw(port, priv);
                 ret |= ((uint32_t) pci_readw(port + 2, priv)) << 16;
+                pci_access_len = 1;
                 break;
         }
     }
@@ -781,8 +804,8 @@ pci_find_slot(uint8_t add_type, uint8_t ignore_slot)
 
 /* Add a PCI card. */
 void
-pci_add_card(uint8_t add_type, uint8_t (*read)(int func, int addr, void *priv),
-             void (*write)(int func, int addr, uint8_t val, void *priv), void *priv, uint8_t *slot)
+pci_add_card(uint8_t add_type, uint8_t (*read)(int func, int addr, int len, void *priv),
+             void (*write)(int func, int addr, int len, uint8_t val, void *priv), void *priv, uint8_t *slot)
 {
     pci_card_desc_t *dev;
 
@@ -853,7 +876,8 @@ pci_register_card(int pci_card)
 
 /* Add an instance of the PCI bridge. */
 void
-pci_add_bridge(uint8_t add_type, uint8_t (*read)(int func, int addr, void *priv), void (*write)(int func, int addr, uint8_t val, void *priv), void *priv, uint8_t *slot)
+pci_add_bridge(uint8_t add_type, uint8_t (*read)(int func, int addr, int len, void *priv),
+               void (*write)(int func, int addr, int len, uint8_t val, void *priv), void *priv, uint8_t *slot)
 {
     pci_card_t *card;
     uint8_t bridge_slot = (add_type == PCI_ADD_NORMAL) ? last_normal_pci_card_id : pci_find_slot(add_type, 0xff);
diff --git a/src/pci_dummy.c b/src/pci_dummy.c
index bceb58c22..e5395bed8 100644
--- a/src/pci_dummy.c
+++ b/src/pci_dummy.c
@@ -38,7 +38,7 @@ pci_dummy_interrupt(int set, pci_dummy_t *dev)
 }
 
 static uint8_t
-pci_dummy_read(uint16_t port, void *priv)
+pci_dummy_read(uint16_t port, UNUSED(int len), void *priv)
 {
     pci_dummy_t *dev = (pci_dummy_t *) priv;
     uint8_t      ret = 0xff;
@@ -90,7 +90,7 @@ pci_dummy_readl(uint16_t port, void *priv)
 }
 
 static void
-pci_dummy_write(uint16_t port, UNUSED(uint8_t val), void *priv)
+pci_dummy_write(uint16_t port, UNUSED(uint8_t val), UNUSED(int len), void *priv)
 {
     pci_dummy_t *dev = (pci_dummy_t *) priv;
 
diff --git a/src/scsi/scsi_buslogic.c b/src/scsi/scsi_buslogic.c
index daeb0a3e4..754750b22 100644
--- a/src/scsi/scsi_buslogic.c
+++ b/src/scsi/scsi_buslogic.c
@@ -1117,7 +1117,7 @@ BuslogicBIOSUpdate(buslogic_data_t *bl)
 }
 
 static uint8_t
-BuslogicPCIRead(UNUSED(int func), int addr, void *priv)
+BuslogicPCIRead(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const x54x_t *dev = (x54x_t *) priv;
 #ifdef ENABLE_BUSLOGIC_LOG
@@ -1203,7 +1203,7 @@ BuslogicPCIRead(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-BuslogicPCIWrite(UNUSED(int func), int addr, uint8_t val, void *priv)
+BuslogicPCIWrite(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     x54x_t          *dev = (x54x_t *) priv;
     buslogic_data_t *bl  = (buslogic_data_t *) dev->ven_data;
diff --git a/src/scsi/scsi_ncr53c8xx.c b/src/scsi/scsi_ncr53c8xx.c
index bc3ecec0b..eef94c916 100644
--- a/src/scsi/scsi_ncr53c8xx.c
+++ b/src/scsi/scsi_ncr53c8xx.c
@@ -2283,7 +2283,7 @@ uint8_t ncr53c8xx_pci_regs[256];
 bar_t   ncr53c8xx_pci_bar[4];
 
 static uint8_t
-ncr53c8xx_pci_read(UNUSED(int func), int addr, void *priv)
+ncr53c8xx_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     ncr53c8xx_t *dev = (ncr53c8xx_t *) priv;
 
@@ -2387,7 +2387,7 @@ ncr53c8xx_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-ncr53c8xx_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+ncr53c8xx_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     ncr53c8xx_t *dev = (ncr53c8xx_t *) priv;
     uint8_t      valxor;
diff --git a/src/scsi/scsi_pcscsi.c b/src/scsi/scsi_pcscsi.c
index 11793f5a9..51aea3f46 100644
--- a/src/scsi/scsi_pcscsi.c
+++ b/src/scsi/scsi_pcscsi.c
@@ -1997,7 +1997,7 @@ esp_bios_disable(esp_t *dev)
 #define EE_ADAPT_OPTION_SCAM_SUPPORT    0x08
 
 static uint8_t
-esp_pci_read(UNUSED(int func), int addr, void *priv)
+esp_pci_read(UNUSED(int func), int addr, int len, void *priv)
 {
     esp_t *dev = (esp_t *) priv;
 
@@ -2009,12 +2009,15 @@ esp_pci_read(UNUSED(int func), int addr, void *priv)
             if (!dev->has_bios || dev->local)
                 return 0x22;
             else {
-                if (nmc93cxx_eeprom_read(dev->eeprom))
-                    return 0x22;
-                else {
-                    dev->eeprom->dev.out = 1;
-                    return 2;
+                uint8_t ret = 0x22;
+
+                if (len == 1) {
+                    /* First byte of address space is AND-ed with EEPROM DO line */
+                    if (!nmc93cxx_eeprom_read(dev->eeprom))
+                        ret &= 0x00;
                 }
+
+                return ret;
             }
             break;
         case 0x01:
@@ -2084,7 +2087,7 @@ esp_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-esp_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+esp_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     esp_t  *dev = (esp_t *) priv;
     uint8_t valxor;
diff --git a/src/sound/snd_audiopci.c b/src/sound/snd_audiopci.c
index 23c4863c7..9a4cb3c6f 100644
--- a/src/sound/snd_audiopci.c
+++ b/src/sound/snd_audiopci.c
@@ -1905,7 +1905,7 @@ update_legacy(es137x_t *dev, uint32_t old_legacy_ctrl)
 }
 
 static uint8_t
-es1370_pci_read(int func, int addr, void *priv)
+es1370_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const es137x_t *dev = (es137x_t *) priv;
 
@@ -2001,7 +2001,7 @@ es1370_pci_read(int func, int addr, void *priv)
 }
 
 static uint8_t
-es1371_pci_read(int func, int addr, void *priv)
+es1371_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const es137x_t *dev = (es137x_t *) priv;
 
@@ -2103,7 +2103,7 @@ es137x_io_set(es137x_t *dev, int set)
 }
 
 static void
-es1370_pci_write(int func, int addr, uint8_t val, void *priv)
+es1370_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     es137x_t *dev = (es137x_t *) priv;
 
@@ -2154,7 +2154,7 @@ es1370_pci_write(int func, int addr, uint8_t val, void *priv)
 }
 
 static void
-es1371_pci_write(int func, int addr, uint8_t val, void *priv)
+es1371_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     es137x_t *dev = (es137x_t *) priv;
 
diff --git a/src/sound/snd_cmi8x38.c b/src/sound/snd_cmi8x38.c
index 9ee003689..d4490ac23 100644
--- a/src/sound/snd_cmi8x38.c
+++ b/src/sound/snd_cmi8x38.c
@@ -966,7 +966,7 @@ cmi8x38_remap(cmi8x38_t *dev)
 }
 
 static uint8_t
-cmi8x38_pci_read(int func, int addr, void *priv)
+cmi8x38_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const cmi8x38_t *dev = (cmi8x38_t *) priv;
     uint8_t          ret = 0xff;
@@ -980,7 +980,7 @@ cmi8x38_pci_read(int func, int addr, void *priv)
 }
 
 static void
-cmi8x38_pci_write(int func, int addr, uint8_t val, void *priv)
+cmi8x38_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     cmi8x38_t *dev = (cmi8x38_t *) priv;
 
diff --git a/src/video/vid_ati_mach64.c b/src/video/vid_ati_mach64.c
index ceaf4224b..8ce13f14d 100644
--- a/src/video/vid_ati_mach64.c
+++ b/src/video/vid_ati_mach64.c
@@ -5129,7 +5129,7 @@ mach64_writel_be(uint32_t addr, uint32_t val, void *priv)
 }
 
 uint8_t
-mach64_pci_read(UNUSED(int func), int addr, void *priv)
+mach64_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const mach64_t *mach64 = (mach64_t *) priv;
 
@@ -5214,7 +5214,7 @@ mach64_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 void
-mach64_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+mach64_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     mach64_t *mach64 = (mach64_t *) priv;
 
diff --git a/src/video/vid_ati_mach8.c b/src/video/vid_ati_mach8.c
index ccb194146..fff9bce3e 100644
--- a/src/video/vid_ati_mach8.c
+++ b/src/video/vid_ati_mach8.c
@@ -7092,7 +7092,7 @@ ati8514_pos_write(uint16_t port, uint8_t val, void *priv)
 }
 
 static uint8_t
-mach32_pci_read(UNUSED(int func), int addr, void *priv)
+mach32_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const mach_t *mach = (mach_t *) priv;
     uint8_t       ret  = 0x00;
@@ -7171,7 +7171,7 @@ mach32_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-mach32_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+mach32_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     mach_t *mach = (mach_t *) priv;
     if ((addr >= 0x30) && (addr <= 0x33) && !mach->has_bios)
diff --git a/src/video/vid_bochs_vbe.c b/src/video/vid_bochs_vbe.c
index 0a41bec2d..d14e92ec1 100644
--- a/src/video/vid_bochs_vbe.c
+++ b/src/video/vid_bochs_vbe.c
@@ -39,6 +39,7 @@
 #include <86box/vid_svga.h>
 #include <86box/vid_svga_render.h>
 #include <86box/pci.h>
+#include <86box/plat_unused.h>
 #include <86box/i2c.h>
 #include <86box/vid_ddc.h>
 
@@ -628,7 +629,7 @@ bochs_vbe_in(uint16_t addr, void *priv)
 }
 
 static uint8_t
-bochs_vbe_pci_read(const int func, const int addr, void *priv)
+bochs_vbe_pci_read(const int func, const int addr, UNUSED(const int len), void *priv)
 {
     const bochs_vbe_t *dev = (bochs_vbe_t *) priv;
     uint8_t            ret = 0x00;
@@ -711,7 +712,7 @@ bochs_vbe_disable_handlers(bochs_vbe_t *dev)
 }
 
 static void
-bochs_vbe_pci_write(const int func, const int addr, const uint8_t val, void *priv)
+bochs_vbe_pci_write(const int func, const int addr, UNUSED(const int len), const uint8_t val, void *priv)
 {
     bochs_vbe_t *dev = (bochs_vbe_t *) priv;
 
diff --git a/src/video/vid_chips_69000.c b/src/video/vid_chips_69000.c
index ef48207e1..2cd6c4162 100644
--- a/src/video/vid_chips_69000.c
+++ b/src/video/vid_chips_69000.c
@@ -2141,7 +2141,7 @@ chips_69000_in(uint16_t addr, void *priv)
 }
 
 static uint8_t
-chips_69000_pci_read(UNUSED(int func), int addr, void *priv)
+chips_69000_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     chips_69000_t *chips = (chips_69000_t *) priv;
     uint8_t        ret   = 0x00;
@@ -2215,7 +2215,7 @@ chips_69000_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-chips_69000_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+chips_69000_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     chips_69000_t *chips = (chips_69000_t *) priv;
 
diff --git a/src/video/vid_cl54xx.c b/src/video/vid_cl54xx.c
index 4161e223e..cec60332e 100644
--- a/src/video/vid_cl54xx.c
+++ b/src/video/vid_cl54xx.c
@@ -3934,7 +3934,7 @@ gd54xx_start_blit(uint32_t cpu_dat, uint32_t count, gd54xx_t *gd54xx, svga_t *sv
 }
 
 static uint8_t
-cl_pci_read(UNUSED(int func), int addr, void *priv)
+cl_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const gd54xx_t *gd54xx = (gd54xx_t *) priv;
     const svga_t   *svga   = &gd54xx->svga;
@@ -4046,7 +4046,7 @@ cl_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-cl_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+cl_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     gd54xx_t     *gd54xx = (gd54xx_t *) priv;
     const svga_t *svga   = &gd54xx->svga;
diff --git a/src/video/vid_et4000w32.c b/src/video/vid_et4000w32.c
index 4abb9a767..18d6b4575 100644
--- a/src/video/vid_et4000w32.c
+++ b/src/video/vid_et4000w32.c
@@ -2652,7 +2652,7 @@ et4000w32p_io_set(et4000w32p_t *et4000)
 }
 
 uint8_t
-et4000w32p_pci_read(UNUSED(int func), int addr, void *priv)
+et4000w32p_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const et4000w32p_t *et4000 = (et4000w32p_t *) priv;
 
@@ -2709,7 +2709,7 @@ et4000w32p_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 void
-et4000w32p_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+et4000w32p_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     et4000w32p_t *et4000 = (et4000w32p_t *) priv;
     svga_t       *svga   = &et4000->svga;
diff --git a/src/video/vid_mga.c b/src/video/vid_mga.c
index 07b0869f7..449b21866 100644
--- a/src/video/vid_mga.c
+++ b/src/video/vid_mga.c
@@ -6337,7 +6337,7 @@ mystique_tvp3026_gpio_write(uint8_t cntl, uint8_t data, void *priv)
 }
 
 static uint8_t
-mystique_pci_read(UNUSED(int func), int addr, void *priv)
+mystique_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     mystique_t *mystique = (mystique_t *) priv;
     uint8_t     ret      = 0x00;
@@ -6574,7 +6574,7 @@ mystique_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-mystique_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+mystique_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     mystique_t *mystique = (mystique_t *) priv;
 
diff --git a/src/video/vid_s3.c b/src/video/vid_s3.c
index fc7499ff6..3965391cb 100644
--- a/src/video/vid_s3.c
+++ b/src/video/vid_s3.c
@@ -458,8 +458,8 @@ static void     s3_accel_out_l(uint16_t port, uint32_t val, void *priv);
 static uint8_t  s3_accel_in(uint16_t port, void *priv);
 static uint16_t s3_accel_in_w(uint16_t port, void *priv);
 static uint32_t s3_accel_in_l(uint16_t port, void *priv);
-static uint8_t  s3_pci_read(int func, int addr, void *priv);
-static void     s3_pci_write(int func, int addr, uint8_t val, void *priv);
+static uint8_t  s3_pci_read(int func, int addr, int len, void *priv);
+static void     s3_pci_write(int func, int addr, int len, uint8_t val, void *priv);
 
 #ifdef ENABLE_S3_LOG
 int s3_do_log = ENABLE_S3_LOG;
@@ -2013,7 +2013,7 @@ s3_accel_write_fifo(s3_t *s3, uint32_t addr, uint8_t val)
         int addr_lo = addr & 1;
         if (svga->crtc[0x53] & 0x08) {
             if ((addr >= 0x08000) && (addr <= 0x0803f))
-                s3_pci_write(0, addr & 0xff, val, s3);
+                s3_pci_write(0, addr & 0xff, 1, val, s3);
         }
 
         switch (addr & 0x1fffe) {
@@ -6736,7 +6736,7 @@ s3_accel_read(uint32_t addr, void *priv)
 
     if (svga->crtc[0x53] & 0x08) {
         if ((addr >= 0x08000) && (addr <= 0x0803f))
-            return s3_pci_read(0, addr & 0xff, s3);
+            return s3_pci_read(0, addr & 0xff, 1, s3);
         switch (addr & 0x1ffff) {
             case 0x83b0 ... 0x83df:
                 return s3_in(addr & 0x3ff, s3);
@@ -11001,7 +11001,7 @@ s3_accel_start(int count, int cpu_input, uint32_t mix_dat, uint32_t cpu_dat, voi
 }
 
 static uint8_t
-s3_pci_read(UNUSED(int func), int addr, void *priv)
+s3_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const s3_t   *s3   = (s3_t *) priv;
     const svga_t *svga = &s3->svga;
@@ -11090,7 +11090,7 @@ s3_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-s3_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+s3_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     s3_t   *s3   = (s3_t *) priv;
     svga_t *svga = &s3->svga;
diff --git a/src/video/vid_s3_virge.c b/src/video/vid_s3_virge.c
index abeba064e..b53dd5e8c 100644
--- a/src/video/vid_s3_virge.c
+++ b/src/video/vid_s3_virge.c
@@ -5024,7 +5024,7 @@ s3_virge_overlay_draw(svga_t *svga, int displine)
 }
 
 static uint8_t
-s3_virge_pci_read(UNUSED(int func), int addr, void *priv)
+s3_virge_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const virge_t *virge = (virge_t *) priv;
     const svga_t  *svga  = &virge->svga;
@@ -5189,7 +5189,7 @@ s3_virge_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 static void
-s3_virge_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+s3_virge_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     virge_t *virge = (virge_t *) priv;
     svga_t  *svga  = &virge->svga;
diff --git a/src/video/vid_tgui9440.c b/src/video/vid_tgui9440.c
index 28c02363c..2a76ee2a4 100644
--- a/src/video/vid_tgui9440.c
+++ b/src/video/vid_tgui9440.c
@@ -1096,7 +1096,7 @@ tgui_hwcursor_draw(svga_t *svga, int displine)
 }
 
 uint8_t
-tgui_pci_read(UNUSED(int func), int addr, void *priv)
+tgui_pci_read(UNUSED(int func), int addr, UNUSED(int len), void *priv)
 {
     const tgui_t *tgui = (tgui_t *) priv;
 
@@ -1166,7 +1166,7 @@ tgui_pci_read(UNUSED(int func), int addr, void *priv)
 }
 
 void
-tgui_pci_write(UNUSED(int func), int addr, uint8_t val, void *priv)
+tgui_pci_write(UNUSED(int func), int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     tgui_t *tgui = (tgui_t *) priv;
     svga_t *svga = &tgui->svga;
diff --git a/src/video/vid_voodoo.c b/src/video/vid_voodoo.c
index 72a57e66c..78aba3cad 100644
--- a/src/video/vid_voodoo.c
+++ b/src/video/vid_voodoo.c
@@ -1005,7 +1005,7 @@ voodoo_recalcmapping(voodoo_set_t *set)
 }
 
 uint8_t
-voodoo_pci_read(int func, int addr, void *priv)
+voodoo_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const voodoo_t *voodoo = (voodoo_t *) priv;
 
@@ -1069,7 +1069,7 @@ voodoo_pci_read(int func, int addr, void *priv)
 }
 
 void
-voodoo_pci_write(int func, int addr, uint8_t val, void *priv)
+voodoo_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     voodoo_t *voodoo = (voodoo_t *) priv;
 
diff --git a/src/video/vid_voodoo_banshee.c b/src/video/vid_voodoo_banshee.c
index f914c7e86..f6f0476ad 100644
--- a/src/video/vid_voodoo_banshee.c
+++ b/src/video/vid_voodoo_banshee.c
@@ -3066,7 +3066,7 @@ banshee_vsync_callback(svga_t *svga)
 }
 
 static uint8_t
-banshee_pci_read(int func, int addr, void *priv)
+banshee_pci_read(int func, int addr, UNUSED(int len), void *priv)
 {
     const banshee_t *banshee = (banshee_t *) priv;
 #if 0
@@ -3276,7 +3276,7 @@ banshee_pci_read(int func, int addr, void *priv)
 }
 
 static void
-banshee_pci_write(int func, int addr, uint8_t val, void *priv)
+banshee_pci_write(int func, int addr, UNUSED(int len), uint8_t val, void *priv)
 {
     banshee_t *banshee = (banshee_t *) priv;
 #if 0