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@xxxxxxxxxxxxxxx wrote: > >>> > >>>> Protocol adaptation layer (PAL) implementation has been added to > >>>> introduce MA-USB structures and logic. > >>>> > >>>> Signed-off-by: Vladimir Stankovic <vladimir.stankovic@xxxxxxxxxxxxxxx> > >>> > >>> ... > >>> > >>>> + /* > >>>> + * 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; > >>> > >>> Removing the SHORT_NOT_OK flag is _not_ a valid thing to do. It will > >>> cause drivers to malfunction. > >>> > >>> Can you please explain this comment? > >>> > >>> What SCSI driver? > >>> > >>> When is the flag being added? > >>> > >>> How does it break USB drives? > >>> > >>> Why haven't you already reported this problem to the > >>> appropriate maintainers? > >>> > >>> Alan Stern > >>> > >> > >> Hi, > >> > >> Issue that removal of SHORT_NOT_OK flag addressed is linked to particular > >> set of Kingston USB 3.0 flash drives (super speed) - other USB flash drives > >> haven't had this flag set. Without this "fix", those Kingston flash drives > >> are not being enumerated properly. > > > > Please explain in detail how the enumeration of these Kingston flash > > drives fails. Or if such an explanation has already been posted, > > please provide a link to it. > > Will reproduce the issue once again (w/o the fix) and run through the events. > Issue has been noticed during early development, and addressed right away. > > > >> This particular line was added in the early stage of development, during > >> enumeration process implementation. The reason why it remained in the code > >> since is because we haven't noticed any side-effects, even with various > >> USB devices being attached to remote MA-USB device, including flash drives, > >> cameras, wireless mice, etc. > > > > Come to think of it, the SHORT_NOT_OK flag is mainly used with HCDs > > that don't have scatter-gather support. Since your mausb driver does > > support scatter-gather, you most likely won't encounter any problems > > unless you go looking for them specifically. > > > >> The problem has been reported, and is actively being investigated. > > > > Where was the problem reported (URL to a mailing list archive)? Who is > > investigating it? > > Ticket has been submitted to DisplayLink's internal issue-tracking system > and is being investigated by mausb-host-devel team. 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
