Hans Verkuil wrote:
> More comments...
>
> On Friday 19 February 2010 20:21:59 Sakari Ailus wrote:
>> Add support for event handling to do_ioctl.
>>
>> Signed-off-by: Sakari Ailus <sakari.ai...@maxwell.research.nokia.com>
>> ---
>> drivers/media/video/v4l2-ioctl.c | 58
>> ++++++++++++++++++++++++++++++++++++++
>> include/media/v4l2-ioctl.h | 7 ++++
>> 2 files changed, 65 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/media/video/v4l2-ioctl.c
>> b/drivers/media/video/v4l2-ioctl.c
>> index 34c7d6e..f7d6177 100644
>> --- a/drivers/media/video/v4l2-ioctl.c
>> +++ b/drivers/media/video/v4l2-ioctl.c
>> @@ -25,6 +25,8 @@
>> #endif
>> #include <media/v4l2-common.h>
>> #include <media/v4l2-ioctl.h>
>> +#include <media/v4l2-fh.h>
>> +#include <media/v4l2-event.h>
>> #include <media/v4l2-chip-ident.h>
>>
>> #define dbgarg(cmd, fmt, arg...) \
>> @@ -1944,7 +1946,63 @@ static long __video_do_ioctl(struct file *file,
>> }
>> break;
>> }
>> + case VIDIOC_DQEVENT:
>> + {
>> + struct v4l2_event *ev = arg;
>> + struct v4l2_fh *vfh = fh;
>> +
>> + if (!test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags)
>> + || vfh->events == NULL)
>> + break;
>
> Change this to:
>
> if (!test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags))
> break;
> if (vfh->events == NULL)
> return -ENOENT;
>
> But see also the next comment.
>
>> +
>> + ret = v4l2_event_dequeue(fh, ev);
>
> There is a crucial piece of functionality missing here: if the filehandle is
> in blocking mode, then it should wait until an event arrives. That also means
> that if vfh->events == NULL, you should still call v4l2_event_dequeue, and
> that function should initialize vfh->events and wait for an event if the fh
> is in blocking mode.
I originally left this out intentionally. Most applications using events
would use select / poll as well by default. For completeness it should
be there, I agree.
This btw. suggests that we perhaps should put back the struct file
argument for the event functions in video_ioctl_ops. The blocking flag
is indeed part of the file structure. I'm open to better suggestions, too.
>> + if (ret < 0) {
>> + dbgarg(cmd, "no pending events?");
>> + break;
>> + }
>> + dbgarg(cmd,
>> + "pending=%d, type=0x%8.8x, sequence=%d, "
>> + "timestamp=%lu.%9.9lu ",
>> + ev->pending, ev->type, ev->sequence,
>> + ev->timestamp.tv_sec, ev->timestamp.tv_nsec);
>> + break;
>> + }
>> + case VIDIOC_SUBSCRIBE_EVENT:
>> + {
>> + struct v4l2_event_subscription *sub = arg;
>> + struct v4l2_fh *vfh = fh;
>>
>> + if (!test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags)
>
> Testing for this bit is unnecessarily. Just test for
> ops->vidioc_subscribe_event.
>
>> + || vfh->events == NULL
>
> Remove this test. If you allocate the event queue only when you first
> subscribe to an event (as ivtv will do), then you have to be able to
> call vidioc_subscribe_event even if vfh->events == NULL.
How about calling v4l2_event_alloc() with zero events? That allocates
and initialises the v4l2_events structure. That's easier to handle in
drivers as well since they don't need to consider special cases like
fh->events happens to be NULL even if events are supported by the
driver. This is how I first thought it'd work.
--
Sakari Ailus
sakari.ai...@maxwell.research.nokia.com
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