Add fixes for multiple sectors per cluster

sw/kernel/filesystems/fat32.h

@@ -12,6 +12,7 @@ extern uint32_t data_start_sector;
 extern uint32_t fat_size;
 extern uint8_t* sd_buf;
 extern uint8_t sectors_per_cluster;
+extern uint8_t log2_sectors_per_cluster;
 
 struct fat32_directory_entry {
     char file_name[8];
@@ -41,7 +42,7 @@ struct lfn_entry {
 };
 
 int8_t fat32_get_cluster_by_name(const char* name, struct fat32_directory_entry* dentry);
-int8_t fat32_read_cluster(uint32_t cluster, void* buf);
+int8_t fat32_read_sector(uint32_t cluster, uint32_t sector, void* buf);
 uint32_t fat32_next_cluster(uint32_t cluster);
 
 int8_t fat32_file_open(const char* filename);

sw/kernel/filesystems/fat32.s

@@ -10,7 +10,7 @@
 .export _fat32_init
 
 .export _root_cluster, _fat_start_sector, _data_start_sector
-.export _fat_size, _sd_buf, _sectors_per_cluster
+.export _fat_size, _sd_buf, _sectors_per_cluster, _log2_sectors_per_cluster
 
 
 .data
@@ -19,6 +19,7 @@ _fat_start_sector: .res 2
 _data_start_sector: .res 4
 _fat_size: .res 4
 _sectors_per_cluster: .res 1
+_log2_sectors_per_cluster: .res 1
 
 _sd_buf: .res 512
 
@@ -52,6 +53,16 @@ root_cluster_offs       = _sd_buf + $2C
     lda sectors_per_cluster
     sta _sectors_per_cluster
 
+    ldx #$0
+@1: bit #$01
+    bne L0
+    inx
+    lsr
+    bra @1
+
+L0: txa
+    sta _log2_sectors_per_cluster
+
     ldx #$00
 L1: lda root_cluster_offs,x
     sta _root_cluster,x

sw/kernel/filesystems/fat32_c.c

@@ -80,9 +80,12 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
     size_t leftover_length;
     size_t bytes_read = 0;
     size_t clusters;
+    uint32_t sector;
     struct pcb* pcb = get_pcb_ptr();
     struct file_desc* fdesc = &pcb->file_desc_array[fd];
-    uint32_t cluster_seq = fdesc->file_pos >> 9;
+
+    uint32_t cluster_seq = fdesc->file_pos >> (9 + log2_sectors_per_cluster);
+
     uint32_t cluster = ((uint32_t)fdesc->f32_dentry.cluster_high << 16) | fdesc->f32_dentry.cluster_low;
 
     /* validate starting position isn't past end of file */
@@ -95,28 +98,30 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
     }
 
 
+    // This can stay for now, as long as cluster_seq is correct.
     for (i = 0; i < cluster_seq; i++) {
         cluster = fat32_next_cluster(cluster);
     }
 
-    // This is an upper bound. It is possible that a 512 chunk can span
-    // 2 clusters, but the first one will already be handled.
-    clusters = nbytes >> 9;
+    clusters = nbytes >> (9 + log2_sectors_per_cluster);
 
 
     /* Handle first unaligned block */
-    offset = fdesc->file_pos % 512;
+    offset = fdesc->file_pos % 512; // This is the offset into the sector, not the cluster
     leftover_length = 512 - offset;
 
+    sector = (fdesc->file_pos >> 9) & (sectors_per_cluster-1);
+
     if (leftover_length != 0) {
         if (nbytes <= leftover_length) {
-            fat32_read_cluster(cluster, sd_buf);
+
+            fat32_read_sector(cluster, sector, sd_buf);
             memcpy(buf, sd_buf + offset, nbytes);
             bytes_read += nbytes;
             fdesc->file_pos += bytes_read;
             return bytes_read;
         } else {
-            fat32_read_cluster(cluster, sd_buf);
+            fat32_read_sector(cluster, sector, sd_buf);
             memcpy(buf, sd_buf + offset, leftover_length);
             bytes_read += leftover_length;
             fdesc->file_pos += bytes_read;
@@ -137,7 +142,7 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
             leftover_length = nbytes - bytes_read;
         }
 
-        fat32_read_cluster(cluster, sd_buf);
+        fat32_read_sector(cluster, cluster, sd_buf);
         memcpy((uint8_t*)buf+bytes_read, sd_buf, leftover_length);
         bytes_read += leftover_length;
         fdesc->file_pos += bytes_read;
@@ -149,9 +154,12 @@ size_t fat32_file_read(int8_t fd, void* buf, size_t nbytes) {
     return bytes_read;
 }
 
-int8_t fat32_read_cluster(uint32_t cluster, void* buf) {
+// Read the sector offset from a given cluster into buf
+// Why do we need this though, this is just doing a single multiplication?
+// No, it is also doing an addition
+int8_t fat32_read_sector(uint32_t cluster, uint32_t sector, void* buf) {
     uint8_t error;
-    uint32_t addr = (cluster - 2) + data_start_sector;
+    uint32_t addr = (cluster - 2) * sectors_per_cluster + sector + data_start_sector;
     SD_readSingleBlock(addr, buf, &error);
     return error;
 }
@@ -176,7 +184,7 @@ int8_t fat32_get_cluster_by_name(const char* name, struct fat32_directory_entry*
 
     cprintf("Sectors per cluster: %hhx\n", sectors_per_cluster);
 
-    fat32_read_cluster(root_cluster, sd_buf);
+    fat32_read_sector(root_cluster, 0, sd_buf);
     for (i = 0; i < 16; i++){
         local_entry = (struct fat32_directory_entry*)(sd_buf + i*32);
         if (local_entry->attr1 == 0xf || local_entry->attr1 & 0x8 || !local_entry->attr1) {

sw/kernel/process/process.c

@@ -1,6 +1,9 @@
 #include <process/process.h>
 
 
+struct pcb fake_pcb;
+
+//TODO
 struct pcb* get_pcb_ptr() {
-    return 0;
+    return &fake_pcb;
 }

sw/test_code/fs_test/main.c

@@ -12,6 +12,8 @@ int main(void) {
     size_t nbytes;
     fat32_init();
 
+    cprintf("log2 sectors per cluster: %x\n", log2_sectors_per_cluster);
+
     /* This is what is going to be part of open */
     fd = fat32_file_open("VERYLA~1TXT");
     cprintf("fd: %x\n", fd);