DOS/ata.c at main · PythonCoders45/DOS · GitHub

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#include "types.h"

#define ATA_PRIMARY_DATA         0x1F0
#define ATA_PRIMARY_ERR          0x1F1
#define ATA_PRIMARY_SECCOUNT     0x1F2
#define ATA_PRIMARY_LBA_LO       0x1F3
#define ATA_PRIMARY_LBA_MID      0x1F4
#define ATA_PRIMARY_LBA_HI       0x1F5
#define ATA_PRIMARY_DRIVE_HEAD   0x1F6
#define ATA_PRIMARY_COMM_REGSTAT 0x1F7

static inline uint8_t inb(uint16_t port) {
    uint8_t ret;
    __asm__ __volatile__ ("inb %1, %0" : "=a"(ret) : "Nd"(port));
    return ret;
}

static inline void outb(uint16_t port, uint8_t val) {
    __asm__ __volatile__ ("outb %0, %1" : : "a"(val), "Nd"(port));
}

static inline uint16_t inw(uint16_t port) {
    uint16_t ret;
    __asm__ __volatile__ ("inw %1, %0" : "=a"(ret) : "Nd"(port));
    return ret;
}

static inline void outw(uint16_t port, uint16_t val) {
    __asm__ __volatile__ ("outw %0, %1" : : "a"(val), "Nd"(port));
}

/**
 * @brief Reads a 512-byte sector from disk into memory buffer
 * @param lba Logical Block Address (Sector number on disk)
 * @param buffer Output memory array (at least 512 bytes)
 */
void ata_read_sector(uint32_t lba, uint8_t* buffer) {
    outb(ATA_PRIMARY_DRIVE_HEAD, 0xE0 | ((lba >> 24) & 0x0F));
    outb(ATA_PRIMARY_SECCOUNT, 1);
    outb(ATA_PRIMARY_LBA_LO, (uint8_t)lba);
    outb(ATA_PRIMARY_LBA_MID, (uint8_t)(lba >> 8));
    outb(ATA_PRIMARY_LBA_HI, (uint8_t)(lba >> 16));
    outb(ATA_PRIMARY_COMM_REGSTAT, 0x20); // 0x20 = Read Sectors Command

    // Wait until disk controller is ready (DRQ bit set, BUSY bit clear)
    while ((inb(ATA_PRIMARY_COMM_REGSTAT) & 0x88) != 0x08);

    // Read 256 16-bit words (512 bytes total)
    uint16_t* ptr = (uint16_t*)buffer;
    for (int i = 0; i < 256; i++) {
        ptr[i] = inw(ATA_PRIMARY_DATA);
    }
}

/**
 * @brief Writes a 512-byte sector from memory buffer to disk
 */
void ata_write_sector(uint32_t lba, uint8_t* buffer) {
    outb(ATA_PRIMARY_DRIVE_HEAD, 0xE0 | ((lba >> 24) & 0x0F));
    outb(ATA_PRIMARY_SECCOUNT, 1);
    outb(ATA_PRIMARY_LBA_LO, (uint8_t)lba);
    outb(ATA_PRIMARY_LBA_MID, (uint8_t)(lba >> 8));
    outb(ATA_PRIMARY_LBA_HI, (uint8_t)(lba >> 16));
    outb(ATA_PRIMARY_COMM_REGSTAT, 0x30); // 0x30 = Write Sectors Command

    while ((inb(ATA_PRIMARY_COMM_REGSTAT) & 0x88) != 0x08);

    uint16_t* ptr = (uint16_t*)buffer;
    for (int i = 0; i < 256; i++) {
        outw(ATA_PRIMARY_DATA, ptr[i]);
    }
}