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SubjectRe: [External] Re: [PATCH v5 5/8] usb: mausb_host: Introduce PAL processing
On Thu, 30 Apr 2020, Vladimir Stankovic wrote:

> On 26.4.20. 22:56, Alan Stern wrote:
> > On Sun, 26 Apr 2020, Vladimir Stankovic wrote:
> >
> >> On 26.4.20. 16:31, Alan Stern wrote:
> >>> On Sun, 26 Apr 2020, Vladimir Stankovic wrote:
> >>>
> >>>> On 26.4.20. 02:32, Alan Stern wrote:
> >>>>> On Sat, 25 Apr 2020 vladimir.stankovic@displaylink.com wrote:
> >>>>>
> >>>>>> Protocol adaptation layer (PAL) implementation has been added to
> >>>>>> introduce MA-USB structures and logic.
> >>>>>>
> >>>>>> Signed-off-by: Vladimir Stankovic <vladimir.stankovic@displaylink.com>
> >>>>>
> >>>>> ...
> >>>>>
> >>>>>> + /*
> >>>>>> + * Masking URB_SHORT_NOT_OK flag as SCSI driver is adding it where it
> >>>>>> + * should not, so it is breaking the USB drive on the linux
> >>>>>> + */
> >>>>>> + urb->transfer_flags &= ~URB_SHORT_NOT_OK;

...

> > Okay. What SCSI driver does the comment refer to? Is it something
> > internal to DisplayLink or is it part of the regular Linux kernel?
> >
> > Alan Stern
> >
> Hi,
>
> Comment was related to the SCSI driver that's part of regular Linux kernel -
> once the remote USB flash drive gets enumerated by host, it would appear as
> directly attached to host and then handled by the kernel.
>
> With current implementation, following messages are being logged:
>
> scsi 3:0:0:0: Direct-Access Kingston DataTraveler 3.0 PMAP PQ: 0 ANSI: 6
> sd 3:0:0:0: Attached scsi generic sg2 type 0
>
> after which the flash drive is usable/accessible from host side.

More context please. Without the log messages preceding this one we
can't tell whether the device is using the usb-storage driver or the
uas driver.

Also, what makes you think the driver is setting the SHORT_NOT_OK flag
at the wrong time? In fact, how can there be a wrong time?
SHORT_NOT_OK is a valid flag to use with any control or bulk URB.

Alan Stern

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