Hi Laurent,

On Tue, Sep 19, 2017 at 03:52:02PM +0300, Laurent Pinchart wrote:

Hi Sakari,

On Tuesday, 19 September 2017 15:04:43 EEST Laurent Pinchart wrote:

quoted

Hi Sakari,

Thank you for the patch.

On Friday, 15 September 2017 17:17:12 EEST Sakari Ailus wrote:

quoted

The information on how many async sub-devices would be bindable to a
notifier is typically dependent on information from platform firmware and
it's not driver's business to be aware of that.

Many V4L2 main drivers are perfectly usable (and useful) without async
sub-devices and so if there aren't any around, just proceed call the
notifier's complete callback immediately without registering the notifier
itself.

If a driver needs to check whether there are async sub-devices available,
it can be done by inspecting the notifier's num_subdevs field which tells
the number of async sub-devices.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <redacted>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

I take this back.

quoted

quoted

---

 drivers/media/v4l2-core/v4l2-async.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-async.c

b/drivers/media/v4l2-core/v4l2-async.c index 9895b610e2a0..4be2f16af051
100644

--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c

@@ -170,14 +170,16 @@ int v4l2_async_notifier_register(struct v4l2_device

*v4l2_dev, struct v4l2_async_subdev *asd;

 	int i;

-	if (!v4l2_dev || !notifier->num_subdevs ||
-	    notifier->num_subdevs > V4L2_MAX_SUBDEVS)
+	if (!v4l2_dev || notifier->num_subdevs > V4L2_MAX_SUBDEVS)

 		return -EINVAL;
 	
 	notifier->v4l2_dev = v4l2_dev;
 	INIT_LIST_HEAD(&notifier->waiting);
 	INIT_LIST_HEAD(&notifier->done);

+	if (!notifier->num_subdevs)
+		return v4l2_async_notifier_call_complete(notifier);
+

This skips adding the notifier to the notifier_list. Won't this result in an 
oops when calling list_del(&notifier->list) in 
v4l2_async_notifier_unregister() ?

Good point. I'll add initialising the list head to the register function,
with an appropriate comment.

quoted

quoted

 	for (i = 0; i < notifier->num_subdevs; i++) {
 	
 		asd = notifier->subdevs[i];

-- 
Regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi