On 03/13/2014 09:13 PM, vkalia@xxxxxxxxxxxxxx wrote:
> Hi
>
> There is a check in __reqbufs in videobuf2-core.c in which if the count is
> same then the function returns immediately. __reqbufs also calls
> queue_setup callback into driver which updates the plane counts and sizes
> of vb2 queue. The count and size can be affected/changed by S_FMT and
> G_FMT ioctl calls. This causes an issue with following call flow:
>
> 1. reqbufs.count = 8;
> ioctl(fd, VIDIOC_REQBUFS, &reqbufs);
> 2. ioctl(fd, VIDIOC_S_FMT, &format) --> update format with differen
> height/width etc which effect the sizeofimage
> 3. reqbufs.count = 8;
> ioctl(fd, VIDIOC_REQBUFS, &reqbufs); to update the vb2_queue num planes
> and size of each plane. But this call never goes to the driver since
> the count is same.
>
> Shouldn't we query the driver for any change in plane count/size before
> deciding to return from reqbufs? Following is the code. This is just a
> temporary patch to point the issue.
>
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c
> b/drivers/media/v4l2-core/videobuf2-core.c
> index e42eb0d..57e18c2 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -590,13 +590,6 @@ static int __reqbufs(struct vb2_queue *q, struct
> v4l2_requestbuffers *req)
> return -EBUSY;
> }
>
> - /*
> - * If the same number of buffers and memory access method is
> requested
> - * then return immediately.
> - */
> - if (q->memory == req->memory && req->count == q->num_buffers)
> - return 0;
> -
What strange kernel version are you using? This obviously wrong code was part of
the first videobuf2 appearance in kernel 2.6.39 and was fixed in 3.0. Furthermore,
in 2.6.39 videobuf2-core.c was in the video directory, not v4l2-core, and the
__reqbufs function didn't exist yet.
It seems someone made a Frankenstein version of videobuf2-core.c for whatever
kernel you are using. A Qualcomm kernel perhaps?
Regards,
Hans
> if (req->count == 0 || q->num_buffers != 0 || q->memory !=
> req->memory) {
> /*
> * We already have buffers allocated, so first check if they
>
> Thanks
> Vinay
>
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