Hi USB team
I'm trying to debug an issue related to sending an ATA command (IDENTIFY
DEVICE = 0xEC) to a SCSI disk connected to a USB port on my PC. After
turning USB/storage debugging on in the kernel, it turns out that the
issue is with a device babble.
A little more kernel instrumentation shows that it's the bulk CSW that
is babbled. The CBW is going through fine, the returned data-in is
correct but the CSW length returned by the device to the USB controller
is more than the expected 13 bytes.
I'm now trying to go further in the debugging process and find out what
is being babbled... The QH overlay is written back properly (including
the token that confirms the babble) but the actual DMA buffer pointed to
by the qh->hw->hw_buf[0] is not. All I can see in this buffer is the
previous command issued in the corresponding CBW (the same DMA buffer is
used for both CBW and CSW).
So, is there any way of figuring out the babbled content - or in other
words, is the babbled content stored anywhere or is it just discarded by
the USB controller as soon as it sees more bytes coming in than expected?
BTW, we're talking about a Bulk endpoint in this case.
Thanks!
Steph
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