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

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On Tue, Oct 05, 2021 at 02:53:48AM +0300, Laurent Pinchart wrote:
> Hi Michael,
> 
> Thank you for resending this.
> 
> On Sun, Oct 03, 2021 at 10:13:55PM +0200, Michael Grzeschik wrote:
> > From: Thomas Haemmerle <thomas.haemmerle@xxxxxxxxxxxxxx>
> > 
> > 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.
> 
> Reflowing the paragraph would be nice (this could be done when applying
> the patch, or not at all).
> 
> > 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@xxxxxxxxxxxxxx>
> > Signed-off-by: Thomas Haemmerle <thomas.haemmerle@xxxxxxxxxxxxxx>
> > Signed-off-by: Michael Tretter <m.tretter@xxxxxxxxxxxxxx>
> > Signed-off-by: Michael Grzeschik <m.grzeschik@xxxxxxxxxxxxxx>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> 
> Felipe, please let me know if you want me to take this in my tree and
> issue a pull request, otherwise I'll assume you'll pick it up.

I'll pick it up now, thanks.

greg k-h



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