Strange issue in USB mass storage device

Strange issue in USB mass storage device

[GN Keshava]

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

Re: Strange issue in USB mass storage device

[Andrew Fish]

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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