On Mon, 07 Dec 2020 09:53:10 +0100, Michael Tretter wrote:
> On Tue, 01 Dec 2020 20:27:30 +0100, Thomas Haemmerle wrote:
> > 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@xxxxxxxxxxxxxx>
>
> While I agree that this driver overall could really use some love, this patch
> at least fixes the driver for user space applications that scan for v4l2
> devices.
>
> Reviewed-By: Michael Tretter <m.tretter@xxxxxxxxxxxxxx>
Ping.
Is there anything missing for getting this patch merged?
Michael
>
> > ---
> > v4:
> > - remove unnecessary inner parentheses
> > - keep and use the local video variable in `uvc_v4l2_release()`
> >
> > v3:
> > - replace `unsigned int connections` with `bool func_connected`
> > - rename `bool connected` to `bool is_uvc_app_handle`
> >
> > v2:
> > - fix deadlock in `uvc_v4l2_unsubscribe_event()` (mutex is already
> > locked in v4l2-core) introduced in v1
> > - lock mutex in `uvc_v4l2_release()` to suppress ioctls and protect
> > connected
> >
> > drivers/usb/gadget/function/uvc.h | 2 ++
> > drivers/usb/gadget/function/uvc_v4l2.c | 49 ++++++++++++++++++++++----
> > 2 files changed, 44 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
> > index 23ee25383c1f..893aaa70f81a 100644
> > --- a/drivers/usb/gadget/function/uvc.h
> > +++ b/drivers/usb/gadget/function/uvc.h
> > @@ -117,6 +117,7 @@ struct uvc_device {
> > enum uvc_state state;
> > struct usb_function func;
> > struct uvc_video video;
> > + bool func_connected;
> >
> > /* Descriptors */
> > struct {
> > @@ -147,6 +148,7 @@ static inline struct uvc_device *to_uvc(struct usb_function *f)
> > struct uvc_file_handle {
> > struct v4l2_fh vfh;
> > struct uvc_video *device;
> > + bool is_uvc_app_handle;
> > };
> >
> > #define to_uvc_file_handle(handle) \
> > diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
> > index 4ca89eab6159..197c26f7aec6 100644
> > --- a/drivers/usb/gadget/function/uvc_v4l2.c
> > +++ b/drivers/usb/gadget/function/uvc_v4l2.c
> > @@ -227,17 +227,55 @@ static int
> > uvc_v4l2_subscribe_event(struct v4l2_fh *fh,
> > const struct v4l2_event_subscription *sub)
> > {
> > + struct uvc_device *uvc = video_get_drvdata(fh->vdev);
> > + struct uvc_file_handle *handle = to_uvc_file_handle(fh);
> > + int ret;
> > +
> > if (sub->type < UVC_EVENT_FIRST || sub->type > UVC_EVENT_LAST)
> > return -EINVAL;
> >
> > - return v4l2_event_subscribe(fh, sub, 2, NULL);
> > + if (sub->type == UVC_EVENT_SETUP && uvc->func_connected)
> > + return -EBUSY;
> > +
> > + ret = v4l2_event_subscribe(fh, sub, 2, NULL);
> > + if (ret < 0)
> > + return ret;
> > +
> > + if (sub->type == UVC_EVENT_SETUP) {
> > + uvc->func_connected = true;
> > + handle->is_uvc_app_handle = true;
> > + uvc_function_connect(uvc);
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static void uvc_v4l2_disable(struct uvc_device *uvc)
> > +{
> > + uvc->func_connected = false;
> > + uvc_function_disconnect(uvc);
> > + uvcg_video_enable(&uvc->video, 0);
> > + uvcg_free_buffers(&uvc->video.queue);
> > }
> >
> > static int
> > uvc_v4l2_unsubscribe_event(struct v4l2_fh *fh,
> > const struct v4l2_event_subscription *sub)
> > {
> > - return v4l2_event_unsubscribe(fh, sub);
> > + struct uvc_device *uvc = video_get_drvdata(fh->vdev);
> > + struct uvc_file_handle *handle = to_uvc_file_handle(fh);
> > + int ret;
> > +
> > + ret = v4l2_event_unsubscribe(fh, sub);
> > + if (ret < 0)
> > + return ret;
> > +
> > + if (sub->type == UVC_EVENT_SETUP && handle->is_uvc_app_handle) {
> > + uvc_v4l2_disable(uvc);
> > + handle->is_uvc_app_handle = false;
> > + }
> > +
> > + return 0;
> > }
> >
> > static long
> > @@ -292,7 +330,6 @@ uvc_v4l2_open(struct file *file)
> > handle->device = &uvc->video;
> > file->private_data = &handle->vfh;
> >
> > - uvc_function_connect(uvc);
> > return 0;
> > }
> >
> > @@ -304,11 +341,9 @@ uvc_v4l2_release(struct file *file)
> > struct uvc_file_handle *handle = to_uvc_file_handle(file->private_data);
> > struct uvc_video *video = handle->device;
> >
> > - uvc_function_disconnect(uvc);
> > -
> > mutex_lock(&video->mutex);
> > - uvcg_video_enable(video, 0);
> > - uvcg_free_buffers(&video->queue);
> > + if (handle->is_uvc_app_handle)
> > + uvc_v4l2_disable(uvc);
> > mutex_unlock(&video->mutex);
> >
> > file->private_data = NULL;
> > --
> > 2.25.1
> >
> >
>
