Hi Sakari,
Some notes on this as well (and that concludes my review):
On Tue, 22 Dec 2009, Sakari Ailus wrote:
Hi,
Here's the second version of the V4L2 file handle and event interface
patchset. Still RFC since I'd like to get more feedback on it.
The first patch adds the V4L2 file handle support and the rest are for V4L2
events.
The patchset works with the OMAP 3 ISP driver. Patches for OMAP 3 ISP are not
part of this patchset but are available in Gitorious (branch is called
events):
git://gitorious.org/omap3camera/mainline.git event
The major change since the last one v4l2_fh structure is now part of driver's
own file handle. It's used as file->private_data as well. I did this based on
Hans Verkuil's suggestion. Sequence numbers and event queue length limitation
is there as well. There are countless of smaller changes, too.
A few notes on the patches:
- I don't like the locking too much. Perhaps the file handle specific lock
(events->lock) could be dropped in favour of the lock for v4l2_file_handle in
video_device?
- Poll. The V4L2 specifiction says:
"When the application did not call VIDIOC_QBUF or
VIDIOC_STREAMON yet the poll() function succeeds, but sets the
POLLERR flag in the revents field."
The current events for OMAP 3 ISP are related to streaming but not all
might be in future. For example there might be some radio or DVB related
events.
I know for sure that we will have to be able to handle events when not
streaming. E.g. events that tell when a HDMI connector was plugged in
or when the EDID was read will need to arrive whether streaming is on
or off.
- Sequence numbers are local to file handles.
That is how it should be.
- Subscribing V4L2_EVENT_ALL causes any other events to be unsubscribed.
- If V4L2_EVENT_ALL has been subscribed, unsubscribing any one of the events
leads to V4L2_EVENT_ALL to be unsubscribed. This problem would be difficult
to work around since this would require the event system to be aware of the
driver private events as well.
Good point. Perhaps attempting to unsubscribe a single event when EVENT_ALL
has been subscribed should result in an error? I.e., you can only unsubscribe
ALL when you subscribed to ALL in the first place.
Regards,
Hans
- If events are missed, the sequence number is incremented in any case. This
way the user space knows events have been missed.
Comments would be very, very welcome.
Cheers,
--
Sakari Ailus
sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
