// pci.h -- PCI configuration space access for DOS/DJGPP
//
// Provides functions to read/write PCI configuration registers and
// enumerate devices on the PCI bus. Uses the standard mechanism 1
// (I/O ports 0xCF8/0xCFC) which is supported by all PCI-capable
// systems from 1993 onward.
//
// All functions operate synchronously via inportl/outportl. No BIOS
// calls (INT 1Ah) are used because mechanism 1 is faster, simpler,
// and doesn't require a DPMI real-mode callback.
#ifndef PCI_H
#define PCI_H

#include <stdint.h>
#include <stdbool.h>

// PCI configuration space register offsets (common header)
#define PCI_VENDOR_ID       0x00
#define PCI_DEVICE_ID       0x02
#define PCI_COMMAND         0x04
#define PCI_STATUS          0x06
#define PCI_REVISION_ID     0x08
#define PCI_CLASS_CODE      0x09
#define PCI_SUBCLASS        0x0A
#define PCI_BASE_CLASS      0x0B
#define PCI_HEADER_TYPE     0x0E
#define PCI_BAR0            0x10
#define PCI_BAR1            0x14
#define PCI_BAR2            0x18
#define PCI_BAR3            0x1C
#define PCI_BAR4            0x20
#define PCI_BAR5            0x24
#define PCI_SUBSYS_VENDOR   0x2C
#define PCI_SUBSYS_ID       0x2E

// PCI command register bits
#define PCI_CMD_IO_ENABLE   0x0001
#define PCI_CMD_MEM_ENABLE  0x0002
#define PCI_CMD_BUS_MASTER  0x0004

// PCI base class for display controllers
#define PCI_CLASS_DISPLAY   0x03

// Maximum PCI bus/device/function values
#define PCI_MAX_BUS         256
#define PCI_MAX_DEV         32
#define PCI_MAX_FUNC        8

// PCI device descriptor returned by enumeration
typedef struct {
    uint8_t  bus;
    uint8_t  dev;
    uint8_t  func;
    uint16_t vendorId;
    uint16_t deviceId;
    uint8_t  revision;
    uint8_t  baseClass;
    uint8_t  subClass;
    uint32_t bar[6];
} PciDeviceT;

// Callback for pciEnumerate(). Return true to stop enumeration.
typedef bool (*PciEnumCallbackT)(const PciDeviceT *device, void *userData);

// ============================================================
// Prototypes
// ============================================================

// Build a CONFIG_ADDRESS dword for the given bus/dev/func/register.
uint32_t pciBuildAddress(uint8_t bus, uint8_t dev, uint8_t func, uint8_t reg);

// Check whether PCI mechanism 1 is available.
bool pciDetect(void);

// Enumerate all PCI devices. Calls cb for each device found.
// Stops early if cb returns true. Returns the number of devices found.
int32_t pciEnumerate(PciEnumCallbackT cb, void *userData);

// Find the first PCI device matching vendorId/deviceId.
// Returns true if found (and fills out dev), false if not.
bool pciFindDevice(uint16_t vendorId, uint16_t deviceId, PciDeviceT *dev);

// Find the first PCI device matching any of the given vendor/device
// pairs. The list is terminated by a {0, 0} entry. Returns true if
// found (and fills out dev and matchIdx), false if not.
bool pciFindDeviceList(const uint16_t *idPairs, PciDeviceT *dev, int32_t *matchIdx);

// Read an 8/16/32-bit value from PCI configuration space.
uint8_t  pciRead8(uint8_t bus, uint8_t dev, uint8_t func, uint8_t reg);
uint16_t pciRead16(uint8_t bus, uint8_t dev, uint8_t func, uint8_t reg);
uint32_t pciRead32(uint8_t bus, uint8_t dev, uint8_t func, uint8_t reg);

// Write an 8/16/32-bit value to PCI configuration space.
void pciWrite8(uint8_t bus, uint8_t dev, uint8_t func, uint8_t reg, uint8_t val);
void pciWrite16(uint8_t bus, uint8_t dev, uint8_t func, uint8_t reg, uint16_t val);
void pciWrite32(uint8_t bus, uint8_t dev, uint8_t func, uint8_t reg, uint32_t val);

#endif // PCI_H