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

[Felipe Balbi <balbi@kernel.org>]

Greg KH <gregkh@linuxfoundation.org> writes:

> 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@wolfvision.net>
>> > 
>> > 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@pengutronix.de>
>> > 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>
>> 
>> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> 
>> 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.

I guess it's too late for an Ack. FWIW:

Acked-by: Felipe Balbi <balbi@kernel.org>

-- 
balbi