4 Commits

Author SHA1 Message Date
aafd4efcb2 Update ata.h
Updated header to match ata.c
2026-01-26 17:18:39 -08:00
d6eb5115d5 Update ata.c
Updated ata.c to include fixed BSY status register
2026-01-26 17:16:31 -08:00
09b2b8cd11 Create ata.c 2026-01-18 17:48:39 -08:00
4079d18a45 Create ata.h
Add base ATA PIO mode driver so that filesystems like fat16 fat32 work.
2026-01-18 17:46:26 -08:00
4 changed files with 163 additions and 187 deletions

119
kernel/ata.c Normal file
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#include "ata.h"
#include "io.h"
#include "print.h"
#define ATA_TIMEOUT 100000
static inline void ata_delay(void) {
/* 400ns delay by reading alternate status */
inb(ATA_PRIMARY_CTRL);
inb(ATA_PRIMARY_CTRL);
inb(ATA_PRIMARY_CTRL);
inb(ATA_PRIMARY_CTRL);
}
bool ata_wait_ready(void) {
for (int i = 0; i < ATA_TIMEOUT; i++) {
uint8_t status = inb(ATA_PRIMARY_IO + ATA_REG_STATUS);
/* Must NOT be busy AND must be ready */
if (!(status & ATA_SR_BSY) && (status & ATA_SR_DRDY))
return true;
}
return false;
}
static bool ata_wait(uint8_t mask) {
for (int i = 0; i < ATA_TIMEOUT; i++) {
uint8_t status = inb(ATA_PRIMARY_IO + ATA_REG_STATUS);
/* If ERR is set, stop waiting and return failure */
if (status & ATA_SR_ERR) return false;
if (!(status & ATA_SR_BSY) && (status & mask))
return true;
}
return false;
}
bool ata_init(void) {
/* Select drive */
outb(ATA_PRIMARY_IO + ATA_REG_HDDEVSEL, ATA_MASTER);
ata_delay();
/* Check if drive exists */
uint8_t status = inb(ATA_PRIMARY_IO + ATA_REG_STATUS);
if (status == 0xFF || status == 0) return false;
outb(ATA_PRIMARY_IO + ATA_REG_COMMAND, ATA_CMD_IDENTIFY);
ata_delay();
if (!ata_wait(ATA_SR_DRQ))
return false;
uint16_t identify[256];
for (int i = 0; i < 256; i++)
identify[i] = inw(ATA_PRIMARY_IO);
print_string("[ATA] Primary master detected\n");
return true;
}
bool ata_read_sector(uint32_t lba, uint8_t* buffer) {
if (!buffer) return false;
/* 1. Wait for drive to be ready for command */
if (!ata_wait_ready()) return false;
/* 2. Setup Task File (LBA28) */
outb(ATA_PRIMARY_IO + ATA_REG_HDDEVSEL, 0xE0 | ((lba >> 24) & 0x0F));
outb(ATA_PRIMARY_IO + ATA_REG_SECCOUNT0, 1);
outb(ATA_PRIMARY_IO + ATA_REG_LBA0, (uint8_t)(lba));
outb(ATA_PRIMARY_IO + ATA_REG_LBA1, (uint8_t)(lba >> 8));
outb(ATA_PRIMARY_IO + ATA_REG_LBA2, (uint8_t)(lba >> 16));
/* 3. Issue Read Command */
outb(ATA_PRIMARY_IO + ATA_REG_COMMAND, ATA_CMD_READ_PIO);
/* 4. Wait for Data Request (DRQ) */
if (!ata_wait(ATA_SR_DRQ))
return false;
/* 5. Transfer data */
for (int i = 0; i < 256; i++) {
uint16_t data = inw(ATA_PRIMARY_IO);
buffer[i * 2] = data & 0xFF;
buffer[i * 2 + 1] = (data >> 8) & 0xFF;
}
ata_delay();
return true;
}
bool ata_write_sector(uint32_t lba, const uint8_t* buffer) {
if (!buffer) return false;
/* 1. Wait for drive to be ready for command */
if (!ata_wait_ready()) return false;
/* 2. Setup Task File */
outb(ATA_PRIMARY_IO + ATA_REG_HDDEVSEL, 0xE0 | ((lba >> 24) & 0x0F));
outb(ATA_PRIMARY_IO + ATA_REG_SECCOUNT0, 1);
outb(ATA_PRIMARY_IO + ATA_REG_LBA0, (uint8_t)(lba));
outb(ATA_PRIMARY_IO + ATA_REG_LBA1, (uint8_t)(lba >> 8));
outb(ATA_PRIMARY_IO + ATA_REG_LBA2, (uint8_t)(lba >> 16));
/* 3. Issue Write Command */
outb(ATA_PRIMARY_IO + ATA_REG_COMMAND, ATA_CMD_WRITE_PIO);
/* 4. Wait for drive to request data */
if (!ata_wait(ATA_SR_DRQ))
return false;
/* 5. Transfer data */
for (int i = 0; i < 256; i++) {
uint16_t word = buffer[i * 2] | (buffer[i * 2 + 1] << 8);
outw(ATA_PRIMARY_IO, word);
}
ata_delay();
return true;
}

44
kernel/ata.h Normal file
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#ifndef ATA_H
#define ATA_H
#include <stdint.h>
#include <stdbool.h>
/* ATA I/O ports */
#define ATA_PRIMARY_IO 0x1F0
#define ATA_PRIMARY_CTRL 0x3F6
/* ATA registers */
#define ATA_REG_DATA 0x00
#define ATA_REG_ERROR 0x01
#define ATA_REG_FEATURES 0x01
#define ATA_REG_SECCOUNT0 0x02
#define ATA_REG_LBA0 0x03
#define ATA_REG_LBA1 0x04
#define ATA_REG_LBA2 0x05
#define ATA_REG_HDDEVSEL 0x06
#define ATA_REG_COMMAND 0x07
#define ATA_REG_STATUS 0x07
/* ATA commands */
#define ATA_CMD_READ_PIO 0x20
#define ATA_CMD_WRITE_PIO 0x30
#define ATA_CMD_IDENTIFY 0xEC
/* Status flags */
#define ATA_SR_BSY 0x80
#define ATA_SR_DRDY 0x40
#define ATA_SR_DRQ 0x08
#define ATA_SR_ERR 0x01
/* Drive select */
#define ATA_MASTER 0xA0
#define ATA_SLAVE 0xB0
/* Public API */
bool ata_init(void);
bool ata_read_sector(uint32_t lba, uint8_t* buffer);
bool ata_write_sector(uint32_t lba, const uint8_t* buffer);
bool ata_wait_ready(void);
#endif

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#include <stddef.h>
#include "vesa.h"
#include "io.h"
#include "print.h"
// VESA mode and controller information
#define VESA_BIOS_INT 0x10
#define VESA_BIOS_FUNC 0x4F
// Function to call BIOS with specific VESA function
static bool vesa_bios_call(uint16_t function, uint16_t* eax, uint32_t* ebx, uint32_t* ecx, uint32_t* edx) {
// Set up registers for VESA function call
__asm__ __volatile__(
"movw %1, %%ax\n" // Move function number into AX
"int $0x10\n" // Call BIOS interrupt 0x10 (VESA)
"movw %%ax, %0\n" // Move return value in AX to the return variable
: "=m"(*eax) // Output operand (eax)
: "m"(function) // Input operand (function number)
: "%eax", "%ebx", "%ecx", "%edx", "memory"
);
// Check for success (return values vary depending on the function)
return *eax == 0x004F;
}
// Set the VESA video mode
bool vesa_set_mode(uint16_t mode) {
uint16_t eax = VBE_FUNCTION_SET_MODE;
uint32_t ebx = mode;
uint32_t ecx = 0;
uint32_t edx = 0;
if (vesa_bios_call(VBE_FUNCTION_SET_MODE, &eax, &ebx, &ecx, &edx)) {
return true;
}
return false;
}
// Get the VESA mode information
bool vesa_get_mode_info(uint16_t mode, vbe_mode_info_t* info) {
uint16_t ax_ret;
// Convert the 32-bit pointer to a Segment:Offset pair
// IMPORTANT: 'info' MUST be located in the first 1MB of RAM
uint32_t ptr = (uint32_t)info;
uint16_t segment = (uint16_t)((ptr >> 4) & 0xFFFF);
uint16_t offset = (uint16_t)(ptr & 0x000F);
__asm__ __volatile__(
"push %%es\n\t" // Save Protected Mode ES
"movw %1, %%es\n\t" // Load the segment into ES
"int $0x10\n\t" // BIOS Interrupt
"pop %%es\n\t" // Restore Protected Mode ES
: "=a"(ax_ret) // Result in AX
: "r"(segment), // %1
"D"(offset), // %2 (DI)
"a"((uint16_t)VBE_FUNCTION_GET_MODE_INFO), // AX (0x4F01)
"c"(mode) // CX (The Mode Number)
: "memory", "cc" // Removed %es from clobbers
);
return ax_ret == 0x004F;
}
bool vesa_get_controller_info(vbe_controller_info_t* info) {
uint16_t ax_ret;
// We must use Segment:Offset for BIOS
uint32_t ptr = (uint32_t)info;
uint16_t segment = (uint16_t)((ptr >> 4) & 0xF000); // Base segment
uint16_t offset = (uint16_t)(ptr & 0xFFFF); // Offset
// Copy "VBE2" into signature to tell BIOS we want VBE 2.0+ info
info->Signature[0] = 'V';
info->Signature[1] = 'B';
info->Signature[2] = 'E';
info->Signature[3] = '2';
// To fix the error: Do not use %es in clobber.
// Use a temporary register or a push/pop sequence if we MUST touch ES.
__asm__ __volatile__(
"push %%es\n\t"
"movw %1, %%es\n\t"
"int $0x10\n\t"
"pop %%es\n\t"
: "=a"(ax_ret)
: "r"(segment), "D"(offset), "a"(0x4F00)
: "memory", "cc"
);
return ax_ret == 0x004F;
}
// Return pointer to the VESA framebuffer
void* vesa_get_framebuffer(void) {
vbe_mode_info_t mode_info;
if (vesa_get_mode_info(0x101, &mode_info)) {
return (void*)mode_info.PhysBasePtr;
}
return NULL;
}
// Clear the screen with a color
void vesa_clear_screen(uint32_t color) {
uint32_t* framebuffer = (uint32_t*)vesa_get_framebuffer();
if (framebuffer) {
for (int y = 0; y < 480; y++) { // For 640x480 mode
for (int x = 0; x < 640; x++) {
framebuffer[y * 640 + x] = color;
}
}
}
}

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#ifndef VESA_H
#define VESA_H
#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>
// VESA BIOS Extension 2.0 Function Calls
#define VBE_FUNCTION_SET_MODE 0x4F02
#define VBE_FUNCTION_GET_MODE_INFO 0x4F01
#define VBE_FUNCTION_GET_CONTROLLER_INFO 0x4F00
#define VBE_FUNCTION_SET_DISPLAY_START 0x4F05
// VESA Mode Information Structure (VBE 2.0)
typedef struct {
uint16_t ModeAttributes; // Mode attributes
uint8_t WinAAttributes; // Window A attributes
uint8_t WinBAttributes; // Window B attributes
uint16_t WinGranularity; // Window granularity
uint16_t WinSize; // Window size
uint16_t WinASegment; // Window A segment address
uint16_t WinBSegment; // Window B segment address
uint32_t WinFuncPtr; // Function pointer for window
uint16_t BytesPerScanLine; // Bytes per scanline
uint16_t XResolution; // Horizontal resolution in pixels
uint16_t YResolution; // Vertical resolution in pixels
uint8_t XCharSize; // Character cell width
uint8_t YCharSize; // Character cell height
uint8_t NumberOfPlanes; // Number of memory planes
uint8_t BitsPerPixel; // Bits per pixel
uint8_t NumberOfBanks; // Number of banks
uint8_t MemoryModel; // Memory model type
uint8_t BankSize; // Bank size in kB
uint8_t NumberOfImagePages; // Number of image pages
uint8_t Reserved0; // Reserved
uint8_t RedMaskSize; // Red mask size
uint8_t RedFieldPosition; // Red field position
uint8_t GreenMaskSize; // Green mask size
uint8_t GreenFieldPosition; // Green field position
uint8_t BlueMaskSize; // Blue mask size
uint8_t BlueFieldPosition; // Blue field position
uint8_t RsvdMaskSize; // Reserved mask size
uint8_t RsvdFieldPosition; // Reserved field position
uint8_t DirectColorModeInfo; // Direct color mode info
uint32_t PhysBasePtr; // Physical base address of the linear framebuffer
uint32_t OffScreenMemOff; // Offset to off-screen memory
uint16_t OffScreenMemSize; // Size of off-screen memory
uint8_t Reserved1[206]; // Reserved
} __attribute__((packed)) vbe_mode_info_t;
// VESA Controller Information
typedef struct {
char Signature[4]; // Should be "VESA" (or "VBE2" for request)
uint16_t Version; // VBE version; high byte is major, low is minor
uint32_t OEMStringPtr; // Segment:Offset pointer to OEM string
uint32_t Capabilities; // Capabilities of graphics controller
uint32_t VideoModePtr; // Segment:Offset pointer to supported modes list
uint16_t TotalMemory; // Number of 64KB memory blocks
uint16_t OEMSoftwareRev; // VBE implementation Software revision
uint32_t OEMVendorNamePtr; // Segment:Offset pointer to Vendor Name string
uint32_t OEMProductNamePtr; // Segment:Offset pointer to Product Name string
uint32_t OEMProductRevPtr; // Segment:Offset pointer to Product Revision string
uint8_t Reserved[222]; // Reserved for VBE implementation scratch area
uint8_t OEMData[256]; // Data area for OEM strings
} __attribute__((packed)) vbe_controller_info_t;
// Function Prototypes
bool vesa_set_mode(uint16_t mode);
bool vesa_get_mode_info(uint16_t mode, vbe_mode_info_t* info);
bool vesa_get_controller_info(vbe_controller_info_t* info);
void* vesa_get_framebuffer(void);
void vesa_clear_screen(uint32_t color);
#endif // VESA_H