72ee48ee89
Currently, the UVC function is activated when open on the corresponding v4l2 device is called. On another open the activation of the function fails since the deactivation counter in `usb_function_activate` equals 0. However the error is not returned to userspace since the open of the v4l2 device is successful. On a close the function is deactivated (since deactivation counter still equals 0) and the video is disabled in `uvc_v4l2_release`, although the UVC application potentially is streaming. Move activation of UVC function to subscription on UVC_EVENT_SETUP because there we can guarantee for a userspace application utilizing UVC. Block subscription on UVC_EVENT_SETUP while another application already is subscribed to it, indicated by `bool func_connected` in `struct uvc_device`. Extend the `struct uvc_file_handle` with member `bool is_uvc_app_handle` to tag it as the handle used by the userspace UVC application. With this a process is able to check capabilities of the v4l2 device without deactivating the function for the actual UVC application. Reviewed-By: Michael Tretter <m.tretter@pengutronix.de> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Thomas Haemmerle <thomas.haemmerle@wolfvision.net> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de> Acked-by: Felipe Balbi <balbi@kernel.org> Link: https://lore.kernel.org/r/20211003201355.24081-1-m.grzeschik@pengutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.