From 4079d18a45845bf593cac8316466248e2bb0b49d Mon Sep 17 00:00:00 2001 From: Gregory Bowne Date: Sun, 18 Jan 2026 17:46:26 -0800 Subject: [PATCH 1/4] Create ata.h Add base ATA PIO mode driver so that filesystems like fat16 fat32 work. --- kernel/ata.h | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 kernel/ata.h diff --git a/kernel/ata.h b/kernel/ata.h new file mode 100644 index 0000000..c503d5c --- /dev/null +++ b/kernel/ata.h @@ -0,0 +1,43 @@ +#ifndef ATA_H +#define ATA_H + +#include +#include + +/* 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 0x00 +#define ATA_SLAVE 0x10 + +/* 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); + +#endif From 09b2b8cd1135166d58bcc984ce33fb7bef835b7b Mon Sep 17 00:00:00 2001 From: Gregory Bowne Date: Sun, 18 Jan 2026 17:48:39 -0800 Subject: [PATCH 2/4] Create ata.c --- kernel/ata.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 kernel/ata.c diff --git a/kernel/ata.c b/kernel/ata.c new file mode 100644 index 0000000..181503e --- /dev/null +++ b/kernel/ata.c @@ -0,0 +1,91 @@ +#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); +} + +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 (!(status & ATA_SR_BSY) && (status & mask)) + return true; + } + return false; +} + +bool ata_init(void) { + outb(ATA_PRIMARY_IO + ATA_REG_HDDEVSEL, 0xA0); // master + ata_delay(); + + outb(ATA_PRIMARY_IO + ATA_REG_COMMAND, ATA_CMD_IDENTIFY); + ata_delay(); + + uint8_t status = inb(ATA_PRIMARY_IO + ATA_REG_STATUS); + if (status == 0) + return false; // no drive + + 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; + + 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)); + outb(ATA_PRIMARY_IO + ATA_REG_COMMAND, ATA_CMD_READ_PIO); + + if (!ata_wait(ATA_SR_DRQ)) + return false; + + 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; + } + + ata_delay(); + return true; +} + +bool ata_write_sector(uint32_t lba, const uint8_t* buffer) { + if (!buffer) return false; + + 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)); + outb(ATA_PRIMARY_IO + ATA_REG_COMMAND, ATA_CMD_WRITE_PIO); + + if (!ata_wait(ATA_SR_DRQ)) + return false; + + 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; +} From d6eb5115d58b9de1a30490b8474ab025533000fc Mon Sep 17 00:00:00 2001 From: Gregory Bowne Date: Mon, 26 Jan 2026 17:16:31 -0800 Subject: [PATCH 3/4] Update ata.c Updated ata.c to include fixed BSY status register --- kernel/ata.c | 46 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 37 insertions(+), 9 deletions(-) diff --git a/kernel/ata.c b/kernel/ata.c index 181503e..20ddd12 100644 --- a/kernel/ata.c +++ b/kernel/ata.c @@ -12,9 +12,22 @@ static inline void ata_delay(void) { 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; } @@ -22,16 +35,17 @@ static bool ata_wait(uint8_t mask) { } bool ata_init(void) { - outb(ATA_PRIMARY_IO + ATA_REG_HDDEVSEL, 0xA0); // master + /* 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(); - uint8_t status = inb(ATA_PRIMARY_IO + ATA_REG_STATUS); - if (status == 0) - return false; // no drive - if (!ata_wait(ATA_SR_DRQ)) return false; @@ -46,20 +60,28 @@ bool ata_init(void) { 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; + buffer[i * 2 + 1] = (data >> 8) & 0xFF; } ata_delay(); @@ -69,20 +91,26 @@ bool ata_read_sector(uint32_t lba, uint8_t* buffer) { 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); + uint16_t word = buffer[i * 2] | (buffer[i * 2 + 1] << 8); outw(ATA_PRIMARY_IO, word); } From aafd4efcb298f36f6977daec31907586937c6669 Mon Sep 17 00:00:00 2001 From: Gregory Bowne Date: Mon, 26 Jan 2026 17:18:39 -0800 Subject: [PATCH 4/4] Update ata.h Updated header to match ata.c --- kernel/ata.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/ata.h b/kernel/ata.h index c503d5c..3da5aff 100644 --- a/kernel/ata.h +++ b/kernel/ata.h @@ -32,12 +32,13 @@ #define ATA_SR_ERR 0x01 /* Drive select */ -#define ATA_MASTER 0x00 -#define ATA_SLAVE 0x10 +#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