Re: [PATCH v4] usb: gadget: uvc: fix multiple opens

[Felipe Balbi <balbi@kernel.org>]

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Hi,

Thomas Haemmerle <thomas.haemmerle@wolfvision.net> writes:
> 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.
>
> Signed-off-by: Thomas Haemmerle <thomas.haemmerle@wolfvision.net>

Laurent, do you agree with the change?

-- 
balbi

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