disk: part_dos: don't claim whole-disk FAT filesystems

Logically, a disk that contains a raw FAT filesystem does not in fact
have a partition table. However, test_part_dos() was claiming that such
disks did in fact have a DOS-style partition table. This caused
get_device_and_partition() not to return a whole-disk disk_partition_t,
since part_type != PART_TYPE_UNKNOWN.

part_dos.c's print_partition_extended() detected the raw FAT filesystem
condition and printed a fake partition table that encompassed the whole
disk.

However, part_dos.c's get_partition_info_extended() did not return any
valid partitions in this case. This combination caused
get_device_and_partition() not to find any valid partitions, and hence
to return an error.

Fix test_part_dos() not to claim that raw FAT filesystems are DOS
partition tables. In turn, this causes get_device_and_partition() to
return a whole-disk disk_partition_t, and hence the following commands
work:

fatls mmc 0 /
fatls mmc 0:auto /

An alternative would be to modify print_partition_extended() to detect
raw FAT filesystems, just like print_partition_extended() does, and to
return a fake partition in this case. However, this seems logically
incorrect, and also duplicates code, since get_device_and_partition()
falls back to returning a whole-disk partition when there is no partition
table on the device.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

diff --git a/disk/part_dos.c b/disk/part_dos.c
index c9a3e2bf02eb8e4e2a76fdd2a93e84f86caccc21..5c454e65abf0fdac5dede7ff0bcc043cd0abfd61 100644 (file)
--- a/disk/part_dos.c
+++ b/disk/part_dos.c
@@ -94,12 +94,13 @@ int test_part_dos (block_dev_desc_t *dev_desc)
 {
        ALLOC_CACHE_ALIGN_BUFFER(unsigned char, buffer, dev_desc->blksz);
 
-       if ((dev_desc->block_read(dev_desc->dev, 0, 1, (ulong *) buffer) != 1) ||
-           (buffer[DOS_PART_MAGIC_OFFSET + 0] != 0x55) ||
-           (buffer[DOS_PART_MAGIC_OFFSET + 1] != 0xaa) ) {
-               return (-1);
-       }
-       return (0);
+       if (dev_desc->block_read(dev_desc->dev, 0, 1, (ulong *) buffer) != 1)
+               return -1;
+
+       if (test_block_type(buffer) != DOS_MBR)
+               return -1;
+
+       return 0;
 }
 
 /*  Print a partition that is relative to its Extended partition table
@@ -117,17 +118,13 @@ static void print_partition_extended (block_dev_desc_t *dev_desc, int ext_part_s
                return;
        }
        i=test_block_type(buffer);
-       if(i==-1) {
+       if (i != DOS_MBR) {
                printf ("bad MBR sector signature 0x%02x%02x\n",
                        buffer[DOS_PART_MAGIC_OFFSET],
                        buffer[DOS_PART_MAGIC_OFFSET + 1]);
                return;
        }
-       if(i==DOS_PBR) {
-               printf ("    1\t\t         0\t%10ld\t%2x\n",
-                       dev_desc->lba, buffer[DOS_PBR_MEDIA_TYPE_OFFSET]);
-               return;
-       }
+
        /* Print all primary/logical partitions */
        pt = (dos_partition_t *) (buffer + DOS_PART_TBL_OFFSET);
        for (i = 0; i < 4; i++, pt++) {