i think it works

code/hal/hal_pci.c

@@ -0,0 +1,63 @@
+// hal_pci.c - PCI configuration space via Mechanism 1 port I/O
+#include "hal_api.h"
+#include <stdint.h>
+
+#define PCI_CONFIG_ADDR  0xCF8
+#define PCI_CONFIG_DATA  0xCFC
+
+static uint32_t MakeAddr(uint8_t bus, uint8_t dev, uint8_t fn, uint8_t reg) {
+    return 0x80000000UL
+         | ((uint32_t)bus << 16)
+         | ((uint32_t)(dev & 0x1F) << 11)
+         | ((uint32_t)(fn  & 0x07) <<  8)
+         | (reg & 0xFC);
+}
+
+static uint32_t PciRead32(uint8_t bus, uint8_t dev, uint8_t fn, uint8_t reg) {
+    __outdword(PCI_CONFIG_ADDR, MakeAddr(bus, dev, fn, reg));
+    return __indword(PCI_CONFIG_DATA);
+}
+
+static void PciWrite32(uint8_t bus, uint8_t dev, uint8_t fn,
+                       uint8_t reg, uint32_t val) {
+    __outdword(PCI_CONFIG_ADDR, MakeAddr(bus, dev, fn, reg));
+    __outdword(PCI_CONFIG_DATA, val);
+}
+
+static bool PciFindDevice(uint16_t vendor, uint16_t device,
+                          uint8_t* outBus, uint8_t* outDev, uint8_t* outFn) {
+    for (int bus = 0; bus < 256; bus++)
+        for (int dev = 0; dev < 32; dev++)
+            for (int fn = 0; fn < 8; fn++) {
+                uint32_t id = PciRead32((uint8_t)bus, (uint8_t)dev, (uint8_t)fn, 0);
+                if ((id & 0xFFFF) == vendor && (id >> 16) == device) {
+                    *outBus = (uint8_t)bus; *outDev = (uint8_t)dev; *outFn = (uint8_t)fn;
+                    return true;
+                }
+            }
+    return false;
+}
+
+static bool PciFindClass(uint8_t classCode, uint8_t subclass,
+                         uint8_t* outBus, uint8_t* outDev, uint8_t* outFn) {
+    for (int bus = 0; bus < 256; bus++)
+        for (int dev = 0; dev < 32; dev++)
+            for (int fn = 0; fn < 8; fn++) {
+                uint32_t id = PciRead32((uint8_t)bus,(uint8_t)dev,(uint8_t)fn,0);
+                if ((id & 0xFFFF) == 0xFFFF) continue;   // no device
+                uint32_t cc = PciRead32((uint8_t)bus,(uint8_t)dev,(uint8_t)fn,8);
+                if (((cc >> 24) & 0xFF) == classCode &&
+                    ((cc >> 16) & 0xFF) == subclass) {
+                    *outBus = (uint8_t)bus; *outDev = (uint8_t)dev; *outFn = (uint8_t)fn;
+                    return true;
+                }
+            }
+    return false;
+}
+
+void HalPciInitialize(HAL_PCI* out) {
+    out->ConfigRead32  = PciRead32;
+    out->ConfigWrite32 = PciWrite32;
+    out->FindDevice    = PciFindDevice;
+    out->FindClass     = PciFindClass;
+}