[U-Boot] Cannot access a FAT filesystem in an El-Torito partition

[Wolfgang Denk]

Dear Kyle,

In message <4EDC0B2F-3D26-48A6-9CD9-0B40D6A01EA4 at boeing.com> you wrote:
> The U-Boot FAT driver appears to manually check for the existence of
> an MS-DOS partition table, even when CONFIG_DOS_PARTITION is present
> and working.
> 
> As a result, it is not possible to use the FAT driver on an ISO9660
> El-Torito boot volume, because it does not have a DOS MBR and does
> not pass the magic number check.
> 
> It looks like the code in the FAT driver to check DOS MBRs is just
> legacy code from before libpart existed, and I would like to remove
> it, except several board configs seem to set CONFIG_CMD_FAT but do
> not set CONFIG_DOS_PARTITION:
>   include/configs/dbau1x00.h
>   include/configs/mv88f6281gtw_ge.h
>   include/configs/hymod.h
>   include/configs/LANTEC.h
>   include/configs/gth2.h
>   include/configs/dreamplug.h
>   include/configs/lacie_kw.h
>   include/configs/dockstar.h
>   include/configs/omap3_evm_common.h
>   include/configs/guruplug.h
>   include/configs/rd6281a.h
>   include/configs/ep8260.h
>   include/configs/sheevaplug.h

Some of these devices are well maintained, others are more or less
dead and have long reached their (commercial, at least) EOL.  It will
probably be impossible to test on all of them.

> Can I just modify those board configs to set CONFIG_DOS_PARTITION
> and remove the duplicated FAT-specific partition-table probing
> code or is there something else I should do?

The best you can do is probbaly 1) provide an easy to reproduce test
case for the problem (for example including an image that can be put
on a USB stick or an SDCard), and 2) submit a patch that implements
your fix. Then at least the boards that are still alive can be
tested.

Best regards,

Wolfgang Denk

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