[U-Boot] [PATCH v1] DOS_PBR block type is also valid dos block type.

[Stephen Warren]

On 03/12/2013 08:58 PM, Sonic Zhang wrote:
> Hi Stephen,
> 
> On Tue, Mar 12, 2013 at 11:09 AM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>> On 03/11/2013 08:57 PM, Sonic Zhang wrote:
>>> Hi Stephen,
>>>
>>>
>>> On Tue, Mar 12, 2013 at 1:28 AM, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>>> On 03/11/2013 03:56 AM, sonic.adi at gmail.com wrote:
>>>>> From: Sonic Zhang <sonic.zhang at analog.com>
>>>>>
>>>>> - Should return 0 for both DOS_MBR and DOS_PBR block types in test_part_dos().
>>>>
>>>> What problem does this solve?
>>>>
>>>> I don't believe this change is correct. The purpose of test_part_dos()
>>>> is to determine whether a block device contains an MS-DOS partition table.
>>>>
>>>> Such a partition table is present in an MBR, but not a PBR. A PBR
>>>> contains a *FAT file-system, and does not include a partition table.
>>>
>>> The SD card formated by windows 7 into one FAT partition can't be
>>> initialized correct in u-boot function init_part() after you reuses
>>> function test_block_type() in function test_part_dos(). So, files on
>>> that partition can't be displayed when run command "fatls mmc 0".
>>>
>>> The only difference in your change is to mark dos partition with flag
>>> DOS_PBR invalid.
>>
>> I did test a raw FAT filesystem on an SD card without any partition
>> table, and it worked fine. Admittedly I created the layout/filesystem
>> with Linux rather than Windows, but I don't think the layout would be
>> any difference. What if you "fatls mmc 0:0" rather than "fatls mmc 0";
>> does that make any difference?
> 
> "fatls mmc 0:0" makes no difference.

I have reproduced this. However, I believe it's not a simple "the code
is wrong" issue, but rather some kind of issue with stale state sticking
around.

In other words, the following works just fine:

========
Reset the board

Insert an SD card with a raw FAT filesystem; no partitions

Tegra20 (SeaBoard) # ls mmc 1
  3637576   zimage
        0   raw-fat-no-partititions

2 file(s), 0 dir(s)
========

(I have a file named raw-fat-no-partitions on the card so I can easily
identify it)

However, the following fails:

========
Reset the board

Insert an SD card with DOS partition table, two partitions, each
containing a FAT filesystem

Tegra20 (SeaBoard) # ls mmc 1
  3637576   zimage
        0   part-id-1

2 file(s), 0 dir(s)

Insert an SD card with a raw FAT filesystem; no partitions

Tegra20 (SeaBoard) # mmc rescan 1
Tegra20 (SeaBoard) # ls mmc 1
** Can't read partition table on 1:0 **
** Invalid partition 1 **
========

(Again, I have a file named part-id-1 on the other card so I can easily
identify it)

This reproduces all the way back to at least commit d1efb64 "disk:
part_dos: don't claim whole-disk FAT filesystems", which is where I
fixed raw-FAT-filesystem-without-partition-tables, and is the change you
wanted to revert.

I'll see if I can track down what's going on.