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media: uvcvideo: Turn on the camera if V4L2_EVENT_SUB_FL_SEND_INITIAL

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If we subscribe to an event with V4L2_EVENT_SUB_FL_SEND_INITIAL, the
driver needs to report back some values that require the camera to be
powered on. But VIDIOC_SUBSCRIBE_EVENT is not part of the ioctls that
turn on the camera.

We could unconditionally turn on the camera during
VIDIOC_SUBSCRIBE_EVENT, but it is more efficient to turn it on only
during V4L2_EVENT_SUB_FL_SEND_INITIAL, which we believe is not a common
usecase.

To avoid a list_del if uvc_pm_get() fails, we move list_add_tail to the
end of the function.

Reviewed-by: Hans de Goede <hansg@kernel.org>
Fixes: d1b618e795 ("media: uvcvideo: Do not turn on the camera for some ioctls")
Cc: stable@vger.kernel.org
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Link: https://lore.kernel.org/r/20250701-uvc-grannular-invert-v4-5-8003b9b89f68@chromium.org
Signed-off-by: Hans de Goede <hansg@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
This commit is contained in:
Ricardo Ribalda
2025-07-01 06:45:17 +00:00
committed by Hans Verkuil
parent 7dd56c4778
commit a03e32e601
1 changed files with 9 additions and 1 deletions
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10
drivers/media/usb/uvc/uvc_ctrl.c
View File

@@ -2072,18 +2072,24 @@ static int uvc_ctrl_add_event(struct v4l2_subscribed_event *sev, unsigned elems)
goto done;
}
list_add_tail(&sev->node, &mapping->ev_subs);
if (sev->flags & V4L2_EVENT_SUB_FL_SEND_INITIAL) {
struct v4l2_event ev;
u32 changes = V4L2_EVENT_CTRL_CH_FLAGS;
s32 val = 0;
ret = uvc_pm_get(handle->chain->dev);
if (ret)
goto done;
if (uvc_ctrl_mapping_is_compound(mapping) ||
__uvc_ctrl_get(handle->chain, ctrl, mapping, &val) == 0)
changes |= V4L2_EVENT_CTRL_CH_VALUE;
uvc_ctrl_fill_event(handle->chain, &ev, ctrl, mapping, val,
changes);
uvc_pm_put(handle->chain->dev);
/*
* Mark the queue as active, allowing this initial event to be
* accepted.
@@ -2092,6 +2098,8 @@ static int uvc_ctrl_add_event(struct v4l2_subscribed_event *sev, unsigned elems)
v4l2_event_queue_fh(sev->fh, &ev);
}
list_add_tail(&sev->node, &mapping->ev_subs);
done:
mutex_unlock(&handle->chain->ctrl_mutex);
return ret;