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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 30.4.20. 17:18, Alan Stern wrote:
    > > 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;
    > >
    > > ...

    > > 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
    > >
    > The comment is clearly wrong - as mentioned earlier, this fix was added in early
    > development phase and I guess that implementer was not clear on how the particular
    > flag was added. Investigation is ongoing around proper fix for this.
    >
    > Anyhow, it is a usb-storage driver related to this - here is usb-related log snippet:
    >
    > usb 3-1.1.2: new high-speed USB device number 5 using mausb_host_hcd_dev
    > usb 3-1.1.2: New USB device found, idVendor=0951, idProduct=1666
    > usb 3-1.1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
    > usb 3-1.1.2: Product: DataTraveler 3.0
    > usb 3-1.1.2: Manufacturer: Kingston
    > usb 3-1.1.2: SerialNumber: 0C9D9210E304E311095E087A
    > usb-storage 3-1.1.2:1.0: USB Mass Storage device detected
    > scsi host3: usb-storage 3-1.1.2:1.0
    > scsi 3:0:0:0: Direct-Access Kingston DataTraveler 3.0 PMAP PQ: 0 ANSI: 6
    > Attached scsi generic sg2 type 0
    > [sdb] 30277632 512-byte logical blocks: (15.5 GB/14.4 GiB)
    >
    > As can be seen, USB flash attached to remote device is properly enumerated via
    > MA USB. Without the fix, usb driver is not able to read USB descriptors, ending
    > up in USB storage not being accessible.

    That's strange, considering that the SHORT_NOT_OK flag doesn't get set
    when the system is reading the device's USB descriptors.

    Alan Stern

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