Re: [PATCH v9 14/15] v4l: Add V4L2_CAP_FENCES to drivers

Hans Verkuil
2018-05-07T12:42:40Z

On 04/05/18 22:06, Ezequiel Garcia wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.com>
>
> Drivers that use videobuf2 are capable of using fences and
> should report that to userspace.
>
> v9: Add in the core.
>
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> ---
> drivers/media/v4l2-core/v4l2-ioctl.c | 8 ++++++++
> include/media/v4l2-fh.h | 2 --
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index f75ad954a6f2..2ae527ef0bc7 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -1002,12 +1002,20 @@ static int v4l_querycap(const struct v4l2_ioctl_ops *ops,
> {
> struct v4l2_capability *cap = (struct v4l2_capability *)arg;
> struct video_device *vfd = video_devdata(file);
> + struct v4l2_fh *vfh =
> + test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
> int ret;
>
> cap->version = LINUX_VERSION_CODE;
> cap->device_caps = vfd->device_caps;
> cap->capabilities = vfd->device_caps | V4L2_CAP_DEVICE_CAPS;
>
> + /* If it has a queue or a m2m context, then the
> + * device supports fence synchronization.
> + */
> + if (vfd->queue || (vfh && vfh->m2m_ctx))
> + cap->device_caps |= V4L2_CAP_FENCES;

This should also be set in cap->capabilities. I would actually do this
after the ops->vidioc_querycap call to avoid drivers overwriting this
capability flag. It also should only be set if device_caps has V4L2_CAP_STREAMING
set (not all drivers do!).

Note that not all m2m drivers use m2m_ctx, so some of them might have to
set the capability manually in the driver.

> +
> ret = ops->vidioc_querycap(file, fh, cap);
>
> cap->capabilities |= V4L2_CAP_EXT_PIX_FORMAT;
> diff --git a/include/media/v4l2-fh.h b/include/media/v4l2-fh.h
> index ea73fef8bdc0..e993ddc06991 100644
> --- a/include/media/v4l2-fh.h
> +++ b/include/media/v4l2-fh.h
> @@ -57,9 +57,7 @@ struct v4l2_fh {
> unsigned int navailable;
> u32 sequence;
>
> -#if IS_ENABLED(CONFIG_V4L2_MEM2MEM_DEV)

I prefer is this #if was kept (so it needs to be added to v4l_querycap as well).

> struct v4l2_m2m_ctx *m2m_ctx;
> -#endif
> };
>
> /**
>

Regards,

Hans