On Wed, Aug 14, 2024 at 04:10:53PM +0200, Greg KH wrote:
> On Wed, Aug 14, 2024 at 09:48:02PM +0800, Xu Yang wrote:
> > On Wed, Aug 14, 2024 at 01:47:23PM +0200, Greg KH wrote:
> > > On Wed, Aug 14, 2024 at 07:25:37PM +0800, Xu Yang wrote:
> > > > Since commit "6acba0345b68 usb:gadget:uvc Do not use worker thread to pump
> > > > isoc usb requests", pump work could only be queued in uvc_video_complete()
> > > > and uvc_v4l2_qbuf(). If VIDIOC_QBUF is executed before VIDIOC_STREAMON,
> > > > we can only depend on uvc_video_complete() to queue pump work. However,
> > > > this requires some free requests in req_ready list. If req_ready list is
> > > > empty all the time, pump work will never be queued and video datas will
> > > > never be pumped to usb controller. Actually, this situation could happen
> > > > when run uvc-gadget with static image:
> > > >
> > > > $ ./uvc-gadget -i 1080p.jpg uvc.0
> > > >
> > > > When capture image from this device, the user app will always block there.
> > > >
> > > > The issue is uvc driver has queued video buffer before streamon, but the
> > > > req_ready list is empty all the time after streamon. This will queue pump
> > > > work in uvcg_video_enable() to fill some request to req_ready list so the
> > > > uvc device could work properly.
> > > >
> > > > Fixes: 6acba0345b68 ("usb:gadget:uvc Do not use worker thread to pump isoc usb requests")
> > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > Signed-off-by: Xu Yang <xu.yang_2@xxxxxxx>
> > > > ---
> > > > drivers/usb/gadget/function/uvc_video.c | 1 +
> > > > 1 file changed, 1 insertion(+)
> > >
> > > Why is this a RESEND? What happened to the first one to require this?
> >
> > I accidentally forgot to cc usb maillist in previous one. So I resend it.
>
> Please always tell us why you are doing something, otherwise we have no
> idea :(
Okay, understand.
Thanks,
Xu Yang
