Down the call stack from the ioctl handler for VIDIOC_STREAMON,
uvc_video_alloc_requests contains a BUG_ON, which in the high level,
triggers when VIDIOC_STREAMON ioctl is issued without VIDIOC_STREAMOFF
being issued previously.
This can happen in a few ways, such as if the userspace uvc gadget
application simply doesn't issue VIDIOC_STREAMOFF. Another way is if
uvc_function_set_alt with alt 0 is called after it is called with 1 but
before VIDIOC_STREAMON is called; in this case, UVC_EVENT_STREAMON will
not be queued to userspace, and therefore userspace will never call
VIDIOC_STREAMOFF.
To fix this, add two more uvc states: starting and stopping. The
starting state starts when uvc_function_set_alt 1 is called, and ends
in uvc_v4l2_streamon, when the state is changed to streaming. The
stopping state starts when uvc_function_set_alt 0 is called, and ends
in uvc_v4l2_streamoff, when the state is changed to connected.
Along with this fix, the completion of the usb status phase needs to be
delayed until uvc_v4l2_streamon/off. This is already the case for
uvc_function_set_alt 1, so add this to when alt is 0. However, the
delayed_status is only incremented when this function returns, so if
uvc_v4l2_streamon/off is called in between returning and incrementing,
then uvc_function_setup_continue will WARN that delayed_status is zero.
To fix this, add and use usb_composite_setup_delay,
which increments the delayed_status. Then, uvc_function_set_alt
returns 0 instead of USB_GADGET_DELAYED_STATUS.
Finally, there is another way to trigger the aforementioned BUG: start
streaming and (physically) disconnect usb. To fix this, call
uvcg_video_enable 0 in uvc_function_disable.
Paul Elder (4):
usb: gadget: uvc: synchronize streamon/off with uvc_function_set_alt
usb: gadget: composite: add function to increment delayed_status
usb: gadget: uvc: synchronize usb status phase delay for
uvc_function_set_alt
usb: gadget: uvc: disable stream when disconnected
drivers/usb/gadget/composite.c | 6 ++++++
drivers/usb/gadget/function/f_uvc.c | 24 +++++++++++++++++++++---
drivers/usb/gadget/function/uvc.h | 2 ++
drivers/usb/gadget/function/uvc_v4l2.c | 21 +++++++++++++++++++--
include/linux/usb/composite.h | 2 ++
5 files changed, 50 insertions(+), 5 deletions(-)
--
2.17.0
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