Control events support for uvcvideo

Hi Mauro,

The following changes since commit bcb2cf6e0bf033d79821c89e5ccb328bfbd44907:

[media] ngene: remove an unneeded condition (2012-04-26 15:29:23 -0300)

are available in the git repository at:
git://linuxtv.org/pinchartl/uvcvideo.git uvcvideo-events

Hans de Goede (10):
media/radio: use v4l2_ctrl_subscribe_event where possible
v4l2-event: Add v4l2_subscribed_event_ops
v4l2-ctrls: Use v4l2_subscribed_event_ops
uvcvideo: Fix a "ignoring return value of ‘__clear_user’" warning
uvcvideo: Refactor uvc_ctrl_get and query
uvcvideo: Move __uvc_ctrl_get() up
uvcvideo: Add support for control events
uvcvideo: Properly report the inactive flag for inactive controls
uvcvideo: Send control change events for slave ctrls when the master changes
uvcvideo: Drop unused ctrl member from struct uvc_control_mapping

 Documentation/video4linux/v4l2-framework.txt |   28 ++-
 drivers/media/radio/radio-isa.c              |   10 +-
 drivers/media/radio/radio-keene.c            |   14 +-
 drivers/media/video/ivtv/ivtv-ioctl.c        |    3 +-
 drivers/media/video/omap3isp/ispccdc.c       |    2 +-
 drivers/media/video/omap3isp/ispstat.c       |    2 +-
 drivers/media/video/uvc/uvc_ctrl.c           |  320 +++++++++++++++++++++----
 drivers/media/video/uvc/uvc_v4l2.c           |   46 +++-
 drivers/media/video/uvc/uvcvideo.h           |   26 ++-
 drivers/media/video/v4l2-ctrls.c             |   58 ++++-
 drivers/media/video/v4l2-event.c             |   71 +++---
 drivers/usb/gadget/uvc_v4l2.c                |    2 +-
 include/media/v4l2-ctrls.h                   |    7 +-
 include/media/v4l2-event.h                   |   24 ++-
 14 files changed, 456 insertions(+), 157 deletions(-)

Regards,

Laurent Pinchart

Hi Laurent,

I know I am very late with this, but I looked through the event/control core changes and I found a locking bug there. I didn't have a chance to review the patch series when HdG posted it earlier this month, so my apologies for coming up with this only now.

The problem is in v4l2-ctrls.c:

index 7023e6d..2a44355 100644
@@ -2381,10 +2381,22 @@ int v4l2_ctrl_s_ctrl(struct v4l2_ctrl *ctrl, s32 val)
 }
 EXPORT_SYMBOL(v4l2_ctrl_s_ctrl);
 
-void v4l2_ctrl_add_event(struct v4l2_ctrl *ctrl,
-                               struct v4l2_subscribed_event *sev)
+static int v4l2_ctrl_add_event(struct v4l2_subscribed_event *sev)
 {
-       v4l2_ctrl_lock(ctrl);
 

This lock...

+       struct v4l2_ctrl_handler *hdl = sev->fh->ctrl_handler;
+       struct v4l2_ctrl_ref *ref;
+       struct v4l2_ctrl *ctrl;
+       int ret = 0;

+
+ mutex_lock(&hdl->lock);

...and this lock are not necessarily the same. If the control was from a subdevice then they will be different. This doesn't happen in uvc, but it will in other drivers.

+
+ ref = find_ref(hdl, sev->id);

The right approach is to use v4l2_ctrl_find here and then call v4l2_ctrl_lock(ctrl), just as was done in the original code.

+ if (!ref) {
+ ret = -EINVAL;
+ goto leave;
+ }
+ ctrl = ref->ctrl;
+

        list_add_tail(&sev->node, &ctrl->ev_subs);
        if (ctrl->type != V4L2_CTRL_TYPE_CTRL_CLASS &&
            (sev->flags & V4L2_EVENT_SUB_FL_SEND_INITIAL)) {
@@ -2396,18 +2408,42 @@ void v4l2_ctrl_add_event(struct v4l2_ctrl *ctrl,
                fill_event(&ev, ctrl, changes);
                v4l2_event_queue_fh(sev->fh, &ev);
        }

- v4l2_ctrl_unlock(ctrl);
+leave:
+ mutex_unlock(&hdl->lock);
+ return ret;
}
-EXPORT_SYMBOL(v4l2_ctrl_add_event);

-void v4l2_ctrl_del_event(struct v4l2_ctrl *ctrl,
- struct v4l2_subscribed_event *sev)
+static void v4l2_ctrl_del_event(struct v4l2_subscribed_event *sev)
{
- v4l2_ctrl_lock(ctrl);
+ struct v4l2_ctrl_handler *hdl = sev->fh->ctrl_handler;
+
+ mutex_lock(&hdl->lock);

Same problem here.

        list_del(&sev->node);

- v4l2_ctrl_unlock(ctrl);
+ mutex_unlock(&hdl->lock);
}
-EXPORT_SYMBOL(v4l2_ctrl_del_event);

So the code should be:

static int v4l2_ctrl_add_event(struct v4l2_subscribed_event *sev)

{
		struct v4l2_ctrl *ctrl = v4l2_ctrl_find(sev->fh->ctrl_handler, sev->id);

		if (ctrl == NULL)
				return -EINVAL;
        v4l2_ctrl_lock(ctrl);
        list_add_tail(&sev->node, &ctrl->ev_subs);
        if (ctrl->type != V4L2_CTRL_TYPE_CTRL_CLASS &&
            (sev->flags & V4L2_EVENT_SUB_FL_SEND_INITIAL)) {
                struct v4l2_event ev;
                u32 changes = V4L2_EVENT_CTRL_CH_FLAGS;

                if (!(ctrl->flags & V4L2_CTRL_FLAG_WRITE_ONLY))
                        changes |= V4L2_EVENT_CTRL_CH_VALUE;
                fill_event(&ev, ctrl, changes);
                v4l2_event_queue_fh(sev->fh, &ev);
        }
        v4l2_ctrl_unlock(ctrl);
		return 0;
}

and:

static void v4l2_ctrl_del_event(struct v4l2_subscribed_event *sev)

{
		struct v4l2_ctrl *ctrl = v4l2_ctrl_find(sev->fh->ctrl_handler, sev->id);

        v4l2_ctrl_lock(ctrl);
        list_del(&sev->node);
        v4l2_ctrl_unlock(ctrl);
}

Regards,

Hans

Hi Hans,

No worries. Thank you for catching the bug, I'll send a new pull request.

Regards,

Laurent Pinchart

Hi Mauro,

A locking bug was present in the previous pull request. Please ignore it and pull this one instead.

The following changes since commit bcb2cf6e0bf033d79821c89e5ccb328bfbd44907:

[media] ngene: remove an unneeded condition (2012-04-26 15:29:23 -0300)

are available in the git repository at:
git://linuxtv.org/pinchartl/uvcvideo.git uvcvideo-events

Hans de Goede (10):
media/radio: use v4l2_ctrl_subscribe_event where possible
v4l2-event: Add v4l2_subscribed_event_ops
v4l2-ctrls: Use v4l2_subscribed_event_ops
uvcvideo: Fix a "ignoring return value of ‘__clear_user’" warning
uvcvideo: Refactor uvc_ctrl_get and query
uvcvideo: Move __uvc_ctrl_get() up
uvcvideo: Add support for control events
uvcvideo: Properly report the inactive flag for inactive controls
uvcvideo: Send control change events for slave ctrls when the master changes
uvcvideo: Drop unused ctrl member from struct uvc_control_mapping

 Documentation/video4linux/v4l2-framework.txt |   28 ++-
 drivers/media/radio/radio-isa.c              |   10 +-
 drivers/media/radio/radio-keene.c            |   14 +-
 drivers/media/video/ivtv/ivtv-ioctl.c        |    3 +-
 drivers/media/video/omap3isp/ispccdc.c       |    2 +-
 drivers/media/video/omap3isp/ispstat.c       |    2 +-
 drivers/media/video/uvc/uvc_ctrl.c           |  320 ++++++++++++++++++++++----
 drivers/media/video/uvc/uvc_v4l2.c           |   46 +++-
 drivers/media/video/uvc/uvcvideo.h           |   26 ++-
 drivers/media/video/v4l2-ctrls.c             |   47 +++-
 drivers/media/video/v4l2-event.c             |   71 +++---
 drivers/usb/gadget/uvc_v4l2.c                |    2 +-
 include/media/v4l2-ctrls.h                   |    7 +-
 include/media/v4l2-event.h                   |   24 ++-
 14 files changed, 447 insertions(+), 155 deletions(-)

Regards,

Laurent Pinchart

Hi Laurent!

I hate to say it, but while you did update v4l2_ctrl_add_event, you forgot to update v4l2_ctrl_del_event as well. That one still has the same locking issue...

Time for a v3 :-)

Regards,

Hans

Hi Hans,

If it wasn't noon already I'd blame it on not having woken up completely :-)

Here it is.

Mauro, could you please pull the following ? Sorry for the noise.

The following changes since commit bcb2cf6e0bf033d79821c89e5ccb328bfbd44907:

[media] ngene: remove an unneeded condition (2012-04-26 15:29:23 -0300)

are available in the git repository at:
git://linuxtv.org/pinchartl/uvcvideo.git uvcvideo-events

Hans de Goede (10):
media/radio: use v4l2_ctrl_subscribe_event where possible
v4l2-event: Add v4l2_subscribed_event_ops
v4l2-ctrls: Use v4l2_subscribed_event_ops
uvcvideo: Fix a "ignoring return value of ‘__clear_user’" warning
uvcvideo: Refactor uvc_ctrl_get and query
uvcvideo: Move __uvc_ctrl_get() up
uvcvideo: Add support for control events
uvcvideo: Properly report the inactive flag for inactive controls
uvcvideo: Send control change events for slave ctrls when the master changes
uvcvideo: Drop unused ctrl member from struct uvc_control_mapping

 Documentation/video4linux/v4l2-framework.txt |   28 ++-
 drivers/media/radio/radio-isa.c              |   10 +-
 drivers/media/radio/radio-keene.c            |   14 +-
 drivers/media/video/ivtv/ivtv-ioctl.c        |    3 +-
 drivers/media/video/omap3isp/ispccdc.c       |    2 +-
 drivers/media/video/omap3isp/ispstat.c       |    2 +-
 drivers/media/video/uvc/uvc_ctrl.c           |  320 ++++++++++++++++++++++----
 drivers/media/video/uvc/uvc_v4l2.c           |   46 +++-
 drivers/media/video/uvc/uvcvideo.h           |   26 ++-
 drivers/media/video/v4l2-ctrls.c             |   41 +++-
 drivers/media/video/v4l2-event.c             |   71 +++---
 drivers/usb/gadget/uvc_v4l2.c                |    2 +-
 include/media/v4l2-ctrls.h                   |    7 +-
 include/media/v4l2-event.h                   |   24 ++-
 14 files changed, 443 insertions(+), 153 deletions(-)

Regards,

Laurent Pinchart