Re: Strange issue in USB mass storage device

[Andrew Fish <afish@apple.com>]

Your device path difference is based on having a partitioning scheme (MBR or GPT) or not. The partition driver will produce block io protocols for all the partitions. The file system driver goes after fixed block offsets.
> On May 22, 2017, at 1:37 AM, GN Keshava <keshava.gn@gmail.com> wrote:
> 
> Hi all,
> 
> I'm testing a USB mass storage device (A linux CDC gadget, which has serial
> and mass storage with FAT32 filesystem) which works fine with Windows.
> 
> I'm booting to UEFI shell using another mass storage device (a thumb drive).
> My device under test (A linux CDC gadget, which has serial and mass
> storage) detects as file system (fsx: ) only if its device path is lesser
> than the thumb drive. Thumb drive detects always.
> Example:
> case 1:
> Thumb drive: PCI.../.../USB(*2,0*)/HD(MBR...
> Device under test: PCI.../.../USB(*6,2*)
> 
> Result: Device under test doesn't mount. But it's just shown as Removable
> block device. Even if I use mount command, its not mounted. I cant access
> files.
> 
> case 2:
> Thumb drive: PCI.../.../USB(*6,0*)/HD(MBR...
> Device under test: PCI.../.../USB(*2,2*)
> 
> Result: Device under test mounts properly as fs2: . I can access files.
> 
> Also, it can be noted that thumb drive is shown as "HD(MBR...)" whereas my
> DUT does not show this part.
> 
> Any pointers would be much appreciated.
> 
> Thanks and regards,
> Keshava
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