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. > >> As soon as it gets addressed properly (w/o global negation of the flag), >> a new patch will be pushed. > > Thank you. > > Alan Stern > -- Regards, Vladimir.
