Create fat16.c

Add implementation for fat16 filesystem

kernel/fat16.c

@@ -0,0 +1,107 @@
+#include "fat16.h"
+#include "ata.h"   // Use ata_read_sector and ata_write_sector
+#include "print.h" // For debugging
+#include <string.h> // For string manipulation
+
+// Global variables
+static fat16_boot_sector_t boot_sector;
+static uint32_t root_dir_sector = FAT16_ROOT_DIR_SECTOR;
+
+// Read a sector from the disk using ATA
+bool read_sector(uint32_t lba, uint8_t* buffer) {
+    return ata_read_sector(lba, buffer);
+}
+
+// Write a sector to the disk using ATA
+bool write_sector(uint32_t lba, const uint8_t* buffer) {
+    return ata_write_sector(lba, buffer);
+}
+
+// Parse the boot sector to retrieve basic file system info
+bool parse_fat16_boot_sector(void) {
+    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
+
+    // Read the boot sector
+    if (!read_sector(FAT16_BOOT_SECTOR, sector_buffer)) {
+        print_string("[FAT16] Failed to read boot sector\n");
+        return false;
+    }
+
+    // Cast to boot sector structure
+    memcpy(&boot_sector, sector_buffer, sizeof(fat16_boot_sector_t));
+
+    // Check for FAT16 signature
+    if (boot_sector.oem_name[0] != 'F' || boot_sector.oem_name[1] != 'A' || boot_sector.oem_name[2] != 'T') {
+        print_string("[FAT16] Invalid FAT16 boot sector signature\n");
+        return false;
+    }
+
+    print_string("[FAT16] FAT16 boot sector parsed successfully\n");
+    return true;
+}
+
+// Parse the root directory
+bool parse_fat16_root_dir(void) {
+    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
+
+    for (int i = 0; i < (boot_sector.max_root_entries / (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t))); i++) {
+        // Read root directory sector
+        if (!read_sector(root_dir_sector + i, sector_buffer)) {
+            print_string("[FAT16] Failed to read root directory sector\n");
+            return false;
+        }
+
+        // Parse the root directory entries
+        for (int j = 0; j < (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t)); j++) {
+            fat16_dir_entry_t* entry = (fat16_dir_entry_t*)&sector_buffer[j * sizeof(fat16_dir_entry_t)];
+            if (entry->name[0] == 0x00) {
+                // End of directory entries
+                return true;
+            }
+            if (entry->name[0] != 0xE5) {
+                // Print file name (8.3 format)
+                char filename[12];
+                strncpy(filename, (char*)entry->name, 8);
+                filename[8] = '.';
+                strncpy(&filename[9], (char*)entry->ext, 3);
+                filename[11] = '\0';
+                print_string(filename);
+                print_string("\n");
+            }
+        }
+    }
+    return true;
+}
+
+// Read a specific directory entry from the FAT16 root directory
+bool read_fat16_entry(uint16_t entry_index, fat16_dir_entry_t* entry) {
+    uint8_t sector_buffer[FAT16_SECTOR_SIZE];
+    uint32_t sector_num = FAT16_ROOT_DIR_SECTOR + (entry_index / (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t)));
+    uint16_t entry_offset = entry_index % (FAT16_SECTOR_SIZE / sizeof(fat16_dir_entry_t));
+
+    // Read the sector
+    if (!read_sector(sector_num, sector_buffer)) {
+        print_string("[FAT16] Failed to read root directory sector\n");
+        return false;
+    }
+
+    // Get the entry
+    memcpy(entry, &sector_buffer[entry_offset * sizeof(fat16_dir_entry_t)], sizeof(fat16_dir_entry_t));
+    return true;
+}
+
+// Mount the FAT16 filesystem
+bool mount_fat16(void) {
+    // Parse the boot sector
+    if (!parse_fat16_boot_sector()) {
+        return false;
+    }
+
+    // Parse the root directory
+    if (!parse_fat16_root_dir()) {
+        return false;
+    }
+
+    print_string("[FAT16] Filesystem mounted successfully\n");
+    return true;
+}

kernel/fat16.h

@@ -0,0 +1,60 @@
+#ifndef FAT16_H
+#define FAT16_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+/* FAT16 Constants */
+#define FAT16_SECTOR_SIZE        512
+#define FAT16_CLUSTER_SIZE       1
+#define FAT16_MAX_FILENAME_LEN   11   // 8.3 format
+#define FAT16_ROOT_DIR_ENTRIES   224  // Fat16 root directory entries (typically 512 bytes per entry)
+
+#define FAT16_BOOT_SECTOR        0
+#define FAT16_FAT1_SECTOR        1
+#define FAT16_FAT2_SECTOR        2
+#define FAT16_ROOT_DIR_SECTOR    19  // First sector of root directory
+
+/* Boot Sector */
+typedef struct {
+    uint8_t jmp[3];               // Jump instruction to code
+    uint8_t oem_name[8];          // OEM Name
+    uint16_t bytes_per_sector;    // Bytes per sector (512)
+    uint8_t sectors_per_cluster;  // Sectors per cluster
+    uint16_t reserved_sectors;    // Reserved sectors
+    uint8_t num_fats;             // Number of FAT tables
+    uint16_t max_root_entries;    // Max number of root directory entries
+    uint16_t total_sectors_16;    // Total sectors in FAT16
+    uint8_t media_type;           // Media type (0xF8 = fixed drive)
+    uint16_t sectors_per_fat;    // Sectors per FAT table
+    uint16_t sectors_per_track;  // Sectors per track (for CHS addressing)
+    uint16_t num_heads;          // Number of heads (for CHS addressing)
+    uint32_t hidden_sectors;     // Hidden sectors (before the partition)
+    uint32_t total_sectors_32;   // Total sectors in FAT16 (extended)
+} __attribute__((packed)) fat16_boot_sector_t;
+
+/* FAT16 Directory Entry */
+typedef struct {
+    uint8_t name[8];   // File name (8 chars)
+    uint8_t ext[3];    // File extension (3 chars)
+    uint8_t attributes; // File attributes (e.g., directory, read-only)
+    uint8_t reserved;   // Reserved
+    uint8_t creation_time[2]; // Creation time
+    uint8_t creation_date[2]; // Creation date
+    uint8_t last_access_date[2]; // Last access date
+    uint8_t first_cluster_high[2]; // High part of first cluster number
+    uint8_t last_mod_time[2];  // Last modification time
+    uint8_t last_mod_date[2];  // Last modification date
+    uint8_t first_cluster_low[2];  // Low part of first cluster number
+    uint32_t file_size;         // File size in bytes
+} __attribute__((packed)) fat16_dir_entry_t;
+
+/* Function Prototypes */
+bool mount_fat16(void);
+bool read_sector(uint32_t lba, uint8_t* buffer);
+bool write_sector(uint32_t lba, const uint8_t* buffer);
+bool parse_fat16_boot_sector(void);
+bool parse_fat16_root_dir(void);
+bool read_fat16_entry(uint16_t entry_index, fat16_dir_entry_t* entry);
+
+#endif // FAT16_H

kernel/vesa.c

@@ -1,98 +0,0 @@
-#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 eax = VBE_FUNCTION_GET_MODE_INFO;
-    uint32_t ebx = mode;
-    uint32_t ecx = 0;
-    uint32_t edx = 0;
-
-    if (vesa_bios_call(VBE_FUNCTION_GET_MODE_INFO, &eax, &ebx, &ecx, &edx)) {
-        // Copy the information into the provided struct
-        uint32_t base = (uint32_t)info;
-        __asm__ __volatile__(
-            "movw %%bx, %%es:%%di\n"
-            : 
-            : "b" (base)
-            : "%es", "%di", "memory"
-        );
-        return true;
-    }
-    return false;
-}
-
-// Get the VESA controller information
-bool vesa_get_controller_info(vbe_controller_info_t* info) {
-    uint16_t eax = VBE_FUNCTION_GET_CONTROLLER_INFO;
-    uint32_t ebx = 0;
-    uint32_t ecx = 0;
-    uint32_t edx = 0;
-
-    if (vesa_bios_call(VBE_FUNCTION_GET_CONTROLLER_INFO, &eax, &ebx, &ecx, &edx)) {
-        // Copy controller information into the provided struct
-        uint32_t base = (uint32_t)info;
-        __asm__ __volatile__(
-            "movw %%bx, %%es:%%di\n"
-            : 
-            : "b" (base)
-            : "%es", "%di", "memory"
-        );
-        return true;
-    }
-    return false;
-}
-
-// 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;
-            }
-        }
-    }
-}

kernel/vesa.h

@@ -1,67 +0,0 @@
-#ifndef VESA_H
-#define VESA_H
-
-#include <stdint.h>
-#include <stdbool.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 {
-    uint8_t VESAVersion[2];       // VESA version
-    uint32_t OEMStringPtr;        // Pointer to OEM string
-    uint8_t Capabilities[4];      // Capabilities of the controller
-    uint32_t VideoModePtr;        // Pointer to supported video modes
-    uint16_t TotalMemory;         // Total video memory (in 64KB)
-    uint8_t Reserved[4];          // Reserved
-} __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