> Hi Hans,
>
> On Monday 18 January 2010 13:58:09 Hans Verkuil wrote:
>> On Tue, 22 Dec 2009, Sakari Ailus wrote:
>> > Limit event queue length to V4L2_MAX_EVENTS. If the queue is full any
>> > further events will be dropped.
>> >
>> > This patch also updates the count field properly, setting it to
>> exactly
>> > to number of further available events.
>> >
>> > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxxxxxxxxxxxxx>
>> > ---
>> > drivers/media/video/v4l2-event.c | 10 +++++++++-
>> > include/media/v4l2-event.h | 5 +++++
>> > 2 files changed, 14 insertions(+), 1 deletions(-)
>
> [snip]
>
>> > diff --git a/include/media/v4l2-event.h b/include/media/v4l2-event.h
>> > index b11de92..69305c6 100644
>> > --- a/include/media/v4l2-event.h
>> > +++ b/include/media/v4l2-event.h
>> > @@ -28,6 +28,10 @@
>> > #include <linux/types.h>
>> > #include <linux/videodev2.h>
>> >
>> > +#include <asm/atomic.h>
>> > +
>> > +#define V4L2_MAX_EVENTS 1024 /* Ought to be enough for everyone. */
>>
>> I think this should be programmable by the driver. Most drivers do not
>> use
>> events at all, so by default it should be 0 or perhaps it can check
>> whether
>> the ioctl callback structure contains the event ioctls and set it to 0
>> or
>> some initial default value.
>>
>> And you want this to be controlled on a per-filehandle basis even. If I
>> look at ivtv, then most of the device nodes will not have events, only
>> a
>> few will support events. And for one device node type I know that there
>> will only be a single event when stopping the streaming, while another
>> device node type will get an event each frame.
>
> Don't you mean per video node instead of per file handle ? In that case we
> could add a new field to video_device structure that must be initialized
> by
> drivers before registering the device.
Yes, that's what I meant (although you state it much more clearly :-) ).
Regards,
Hans
>> So being able to adjust the event queue dynamically will give more
>> control
>> and prevent unnecessary waste of memory resources.
>
> --
> Regards,
>
> Laurent Pinchart
>
--
Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom
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