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_STREAMOFF 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 is entered when uvc_function_set_alt 1 is called, and is
exited in uvc_v4l2_streamon, when the state is changed to streaming. The
stopping state is entered when uvc_function_set_alt 0 is called, and is
exited in uvc_v4l2_streamoff, when the state is changed to connected.
The status phase of the SET_INTERFACE request doesn't need to be delayed
by the uvc gadget driver, so that is removed.
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.
Changes in v3:
- add state guard to uvc_function_set_alt 1
- add documentation for newly added uvc states
- reorder uvc states to more or less follow the flow diagram
- add more state guards to ioctl handlers for streamon and streamoff
- added interrupt-safe uvcg_video_cancel and used instead of the
non-interrupt-save uvcg_video_enable 0 in uvc_function_disable
Changes in v2:
1. Remove delay usb status phase
Paul Elder (4):
usb: gadget: uvc: synchronize streamon/off with uvc_function_set_alt
usb: gadget: uvc: don't delay the status phase of non-zero
SET_INTERFACE requests
usb: gadget: uvc: disable stream when disconnected
usb: gadget: uvc: remove unused/duplicate function prototypes from
uvc.h
drivers/usb/gadget/function/f_uvc.c | 23 ++++++++----
drivers/usb/gadget/function/uvc.h | 47 +++++++++++++++++++------
drivers/usb/gadget/function/uvc_v4l2.c | 28 +++++++++++----
drivers/usb/gadget/function/uvc_video.c | 13 +++++++
drivers/usb/gadget/function/uvc_video.h | 2 ++
5 files changed, 91 insertions(+), 22 deletions(-)
--
2.20.1
