Factor out fake partition

2 files changed, 86 insertions, 7 deletions

diff --git a/supervisor/shared/filesystem.c b/supervisor/shared/filesystem.c
index ebbc8c40d..de9af5707 100644
--- a/supervisor/shared/filesystem.c
+++ b/supervisor/shared/filesystem.c
@@ -59,7 +59,7 @@ void filesystem_init(bool create_allowed, bool force_create) {
         // Flush the new file system to make sure it's repaired immediately.
         supervisor_flash_flush();
         if (res != FR_OK) {
-            asm("bkpt");
+            //asm("bkpt");
             return;
         }
 
@@ -75,7 +75,7 @@ void filesystem_init(bool create_allowed, bool force_create) {
         // and ensure everything is flushed
         supervisor_flash_flush();
     } else if (res != FR_OK) {
-        asm("bkpt");
+        //asm("bkpt");
         return;
     }
     mp_vfs_mount_t *vfs = &_mp_vfs;
diff --git a/supervisor/shared/flash.c b/supervisor/shared/flash.c
index 4fa2d8f75..c8921aa85 100644
--- a/supervisor/shared/flash.c
+++ b/supervisor/shared/flash.c
@@ -31,6 +31,8 @@
 
 #define VFS_INDEX 0
 
+#define PART1_START_BLOCK (0x1)
+
 void supervisor_flash_set_usb_writable(bool usb_writable) {
     mp_vfs_mount_t* current_mount = MP_STATE_VM(vfs_mount_table);
     for (uint8_t i = 0; current_mount != NULL; i++) {
@@ -63,10 +65,87 @@ STATIC mp_obj_t supervisor_flash_obj_make_new(const mp_obj_type_t *type, size_t
     return (mp_obj_t)&supervisor_flash_obj;
 }
 
+uint32_t flash_get_block_count(void) {
+    return PART1_START_BLOCK + supervisor_flash_get_block_count();
+}
+
+static void build_partition(uint8_t *buf, int boot, int type, uint32_t start_block, uint32_t num_blocks) {
+    buf[0] = boot;
+
+    if (num_blocks == 0) {
+        buf[1] = 0;
+        buf[2] = 0;
+        buf[3] = 0;
+    } else {
+        buf[1] = 0xff;
+        buf[2] = 0xff;
+        buf[3] = 0xff;
+    }
+
+    buf[4] = type;
+
+    if (num_blocks == 0) {
+        buf[5] = 0;
+        buf[6] = 0;
+        buf[7] = 0;
+    } else {
+        buf[5] = 0xff;
+        buf[6] = 0xff;
+        buf[7] = 0xff;
+    }
+
+    buf[8] = start_block;
+    buf[9] = start_block >> 8;
+    buf[10] = start_block >> 16;
+    buf[11] = start_block >> 24;
+
+    buf[12] = num_blocks;
+    buf[13] = num_blocks >> 8;
+    buf[14] = num_blocks >> 16;
+    buf[15] = num_blocks >> 24;
+}
+
+mp_uint_t flash_read_blocks(uint8_t *dest, uint32_t block_num, uint32_t num_blocks) {
+    if (block_num == 0) {
+        if (block_num > 1) {
+            return 1; // error
+        }
+        // fake the MBR so we can decide on our own partition table
+
+        for (int i = 0; i < 446; i++) {
+            dest[i] = 0;
+        }
+
+        build_partition(dest + 446, 0, 0x01 /* FAT12 */, PART1_START_BLOCK, supervisor_flash_get_block_count());
+        build_partition(dest + 462, 0, 0, 0, 0);
+        build_partition(dest + 478, 0, 0, 0, 0);
+        build_partition(dest + 494, 0, 0, 0, 0);
+
+        dest[510] = 0x55;
+        dest[511] = 0xaa;
+
+        return 0; // ok
+
+    }
+    return supervisor_flash_read_blocks(dest, block_num - PART1_START_BLOCK, num_blocks);
+}
+
+mp_uint_t flash_write_blocks(const uint8_t *src, uint32_t block_num, uint32_t num_blocks) {
+    if (block_num == 0) {
+        if (num_blocks > 1) {
+            return 1; // error
+        }
+        // can't write MBR, but pretend we did
+        return 0;
+    } else {
+        return supervisor_flash_write_blocks(src, block_num - PART1_START_BLOCK, num_blocks);
+    }
+}
+
 STATIC mp_obj_t supervisor_flash_obj_readblocks(mp_obj_t self, mp_obj_t block_num, mp_obj_t buf) {
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(buf, &bufinfo, MP_BUFFER_WRITE);
-    mp_uint_t ret = supervisor_flash_read_blocks(bufinfo.buf, mp_obj_get_int(block_num), bufinfo.len / FILESYSTEM_BLOCK_SIZE);
+    mp_uint_t ret = flash_read_blocks(bufinfo.buf, mp_obj_get_int(block_num), bufinfo.len / FILESYSTEM_BLOCK_SIZE);
     return MP_OBJ_NEW_SMALL_INT(ret);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_3(supervisor_flash_obj_readblocks_obj, supervisor_flash_obj_readblocks);
@@ -74,7 +153,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_3(supervisor_flash_obj_readblocks_obj, supervisor
 STATIC mp_obj_t supervisor_flash_obj_writeblocks(mp_obj_t self, mp_obj_t block_num, mp_obj_t buf) {
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(buf, &bufinfo, MP_BUFFER_READ);
-    mp_uint_t ret = supervisor_flash_write_blocks(bufinfo.buf, mp_obj_get_int(block_num), bufinfo.len / FILESYSTEM_BLOCK_SIZE);
+    mp_uint_t ret = flash_write_blocks(bufinfo.buf, mp_obj_get_int(block_num), bufinfo.len / FILESYSTEM_BLOCK_SIZE);
     return MP_OBJ_NEW_SMALL_INT(ret);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_3(supervisor_flash_obj_writeblocks_obj, supervisor_flash_obj_writeblocks);
@@ -85,7 +164,7 @@ STATIC mp_obj_t supervisor_flash_obj_ioctl(mp_obj_t self, mp_obj_t cmd_in, mp_ob
         case BP_IOCTL_INIT: supervisor_flash_init(); return MP_OBJ_NEW_SMALL_INT(0);
         case BP_IOCTL_DEINIT: supervisor_flash_flush(); return MP_OBJ_NEW_SMALL_INT(0); // TODO properly
         case BP_IOCTL_SYNC: supervisor_flash_flush(); return MP_OBJ_NEW_SMALL_INT(0);
-        case BP_IOCTL_SEC_COUNT: return MP_OBJ_NEW_SMALL_INT(supervisor_flash_get_block_count());
+        case BP_IOCTL_SEC_COUNT: return MP_OBJ_NEW_SMALL_INT(flash_get_block_count());
         case BP_IOCTL_SEC_SIZE: return MP_OBJ_NEW_SMALL_INT(supervisor_flash_get_block_size());
         default: return mp_const_none;
     }
@@ -114,10 +193,10 @@ void supervisor_flash_init_vfs(fs_user_mount_t *vfs) {
     vfs->fatfs.part = 1; // flash filesystem lives on first partition
     vfs->readblocks[0] = (mp_obj_t)&supervisor_flash_obj_readblocks_obj;
     vfs->readblocks[1] = (mp_obj_t)&supervisor_flash_obj;
-    vfs->readblocks[2] = (mp_obj_t)supervisor_flash_read_blocks; // native version
+    vfs->readblocks[2] = (mp_obj_t)flash_read_blocks; // native version
     vfs->writeblocks[0] = (mp_obj_t)&supervisor_flash_obj_writeblocks_obj;
     vfs->writeblocks[1] = (mp_obj_t)&supervisor_flash_obj;
-    vfs->writeblocks[2] = (mp_obj_t)supervisor_flash_write_blocks; // native version
+    vfs->writeblocks[2] = (mp_obj_t)flash_write_blocks; // native version
     vfs->u.ioctl[0] = (mp_obj_t)&supervisor_flash_obj_ioctl_obj;
     vfs->u.ioctl[1] = (mp_obj_t)&supervisor_flash_obj;
 }