Create fat16.c

Add implementation for fat16 filesystem

kernel/display.c

@@ -1,80 +1,36 @@
-#include <string.h>
 #include "display.h"
-#include "io.h"
+#include "io.h" // Include your I/O header for port access
 #include "vga.h"
 
 // Initialize the display
 void init_display(void) {
-    // Initialize the VGA driver. This typically sets up the 80x25 text mode,
+    // Initialize VGA settings, if necessary
-    // clears the screen, and sets the cursor.
+    // This could involve setting up the VGA mode, etc.
-    vga_init();
+    set_display_mode(0x13); // Example: Set to 320x200 256-color mode
 }
 
 // Enumerate connected displays
 void enumerate_displays(void) {
-    // This function is often a complex operation in a real driver.
+    // This is a simplified example. Actual enumeration may require
-    // In this simplified kernel/VGA text mode environment, we use printf
+    // reading from specific VGA registers or using BIOS interrupts.
-    // to output a message and rely on the fact that VGA is present.
     
-    // Clear the display before printing a message
+    // For demonstration, we will just print a message
-    vga_clear(vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK));
+    // In a real driver, you would check the VGA registers
-    
+    // to determine connected displays.
-    // Output a simplified enumeration message
+    clear_display();
-    vga_printf("Display: Standard VGA Text Mode (80x25) Detected.\n");
+    // Here you would typically read from VGA registers to find connected displays
-    
+    // For example, using inb() to read from VGA ports
-    // In a real driver, you would use inb() and outb() with specific VGA ports
-    // to read information (e.g., from the CRTC registers 0x3D4/0x3D5)
-    // to check for display presence or configuration.
 }
 
 // Set the display mode
-// NOTE: Setting arbitrary VGA modes (like 0x13 for 320x200) is very complex
-// and requires writing hundreds of register values, often done via BIOS in
-// real mode. Since we are in protected mode and have a simple text driver,
-// this function is kept simple or treated as a placeholder for full mode changes.
 void set_display_mode(uint8_t mode) {
-    // Check if the requested mode is a known mode (e.g., VGA Text Mode 3)
+    // Set the VGA mode by writing to the appropriate registers
-    // For this example, we simply acknowledge the call.
+    outb(VGA_PORT, mode); // Example function to write to a port
-    // A true mode set would involve complex register sequencing.
-    
-    // The provided vga.c is a Text Mode driver, so a graphical mode set
-    // like 0x13 (320x200 256-color) would break the existing vga_printf functionality.
-    
-    // A simplified text-mode-specific response:
-    if (mode == 0x03) { // Mode 3 is standard 80x25 text mode
-        vga_printf("Display mode set to 80x25 Text Mode (Mode 0x03).\n");
-        vga_init(); // Re-initialize the text mode
-    } else {
-        // Simple I/O example based on the original structure (Caution: Incomplete for full mode set)
-        outb(VGA_PORT, mode); // Example function to write to a port
-        vga_printf("Attempting to set display mode to 0x%x. (Warning: May break current display)\n", mode);
-    }
 }
 
 // Clear the display
 void clear_display(void) {
-    // Use the VGA driver's clear function, typically clearing to black on light grey
+    // Clear the display by filling it with a color
-    // or black on black. We'll use the black on light grey from vga_init for consistency.
+    // This is a placeholder for actual clearing logic
-    vga_clear(vga_entry_color(VGA_COLOR_BLACK, VGA_COLOR_LIGHT_GREY));
+    // You would typically write to video memory here
-    // Reset cursor to 0, 0
-    vga_set_cursor_position(0, 0);
-}
-
-// Helper function to write a string
-void display_write_string(const char* str) {
-    // Use the VGA driver's string writing function
-    vga_write_string(str, strlen(str));
-}
-
-// Helper function to print a formatted string
-void display_printf(const char* format, ...) {
-    // Use the VGA driver's printf function
-    va_list args;
-    va_start(args, format);
-    
-    // The vga_printf function already handles the va_list internally,
-    // so we can just call it directly.
-    vga_printf(format, args);
-    
-    va_end(args);
 }

kernel/display.h

@@ -2,21 +2,13 @@
 #define DISPLAY_H
 
 #include <stdint.h>
-#include "vga.h" // Include VGA functions
 
-#define VGA_PORT 0x3C0  // Base port for VGA (Often used for general control, though 0x3D4/0x3D5 are used for cursor)
+#define VGA_PORT 0x3C0  // Base port for VGA
 
 // Function prototypes
 void init_display(void);
 void enumerate_displays(void);
-void set_display_mode(uint8_t mode); // In this context, modes are typically BIOS or VESA modes, which are complex.
+void set_display_mode(uint8_t mode);
-                                      // We'll treat this as a placeholder/simple mode call.
 void clear_display(void);
 
-// New function to write a string using the VGA driver
-void display_write_string(const char* str);
-
-// New function to print a formatted string using the VGA driver
-void display_printf(const char* format, ...);
-
 #endif // DISPLAY_H

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/vga.c

@@ -1,9 +1,9 @@
+#include "vga.h"
 #include <stddef.h>
 #include <stdbool.h>
 #include <string.h>
 #include <stdarg.h>
 #include "string_utils.h"
-#include "vga.h"
 
 void outb(uint16_t port, uint8_t value) {
     __asm__ volatile("outb %0, %1" : : "a"(value), "Nd"(port));
@@ -134,7 +134,7 @@ void vga_printf(const char* format, ...) {
     va_end(args);
     
     // Now you can use the buffer with vga_write_string
-    vga_write_string(buffer, strlen(buffer)); // Use my_strlen instead of strlen
+    vga_write_string(buffer, my_strlen(buffer)); // Use my_strlen instead of strlen
 }
 
 void vga_init(void) {

kernel/vga.h

@@ -35,7 +35,6 @@ typedef enum {
 // Function prototypes
 uint8_t vga_entry_color(vga_color fg, vga_color bg);
 uint16_t vga_entry(unsigned char uc, uint8_t color);
-void vga_init(void);
 
 void vga_put_entry_at(char c, uint8_t color, size_t x, size_t y);
 void vga_clear(uint8_t color);