RE: The Linux FAT issue on SD Cards.. maintainer support please

[Mukund JB.]

Dear Lennart,

I have bought a "entermultimedia" USB 2.0 21-in-1 card.
There are no Linux driver support in the CD  provided.
Can u suggest me what is best bug (USB card reader) with Linux driver
support in the Market.

Regards,
Mukund Jampala

>-----Original Message-----
>From: Lennart Sorensen [mailto:lsorense@xxxxxxxxxxxxxxxxxxx]
>Sent: Thursday, August 11, 2005 9:04 PM
>To: Mukund JB.
>Cc: hirofumi@xxxxxxxxxxxxxxxxxx; linux-kernel-Mailing-list
>Subject: Re: The Linux FAT issue on SD Cards.. maintainer support
please
>
>On Thu, Aug 11, 2005 at 10:57:14AM +0530, Mukund JB. wrote:
>> I am Linux driver programmer.
>>
>> I have a FAT12 issue on my SD cards. I have got these addresses from
the
>> fs-lists as the maintainer support mail IDs for FAT-FS.
>>
>> I am using the 2.6.10 kernel, X86 like systems.
>>
>> I am NOT able to mount the Camera formatted FAT12 filesystem on my
linux
>> BOX. SD card is of size 16MB. At the same time I am able to mount the
SD
>> cards formatted in windows & linux.
>>
>> I have identified fat_fill_super() in fs/fat/inode.c file as the
>> function that reads the super block of as MS-DOS FS.
>>
>> To debug, I have rebuilt my kernel 2.6.10 inserting some debug
messages
>> in the FS sub-system to know what data is coming into "struct
>> fat_boot_sector *b" structure in fs/fat/inode.c file after sb_bread()
>> call.
>>
>> I believe that this data in the "struct fat_boot_sector *b" should be
>> FAT12 information.
>>
>> On the camera formatted SD that is NOT mounting I have found this
>> structure to be all '0' till total_sectors variable (relevant till
here
>> on - FAT12).
>>
>> Will you please verify if there & tell me if the problem is in the
FAT
>> sub-system.
>
>A few things I would try:
>
>Stick the SD card in a generic cheap USB media reader, and see what the
>kernel thinks of the cards then.  Do both work?
>
>If the answer is still no, then it really seems the card is formated
>incorrectly, or linux has a bug in the fat driver.
>
>If both work fine that way, then there is a problem in the driver for
>the sd reader you are using that needs to be resolved.
>
>Using a known to work for people in general driver (usb-storage) with
>a standard usb card reader sure does seem like a good start until you
>know if the card is formated properly or not.
>
>You could also use that do dd the first few blocks from the card to see
>what the partition table and fat tables look like, in case your SD
>driver is somehow messing that part up.  By having a copy you can
>compare more easily.
>
>Len Sorensen

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