linux-kernel - Re: [RFC][PATCHv2 09/12] videobuf2: let user-space know if driver supports cache hints

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Message-ID: <2a00bf5c-462e-8d35-844c-55ce2383b8e2@xs4all.nl>
Date:   Wed, 19 Feb 2020 09:33:38 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Sakari Ailus <sakari.ailus@....fi>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Pawel Osciak <posciak@...omium.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCHv2 09/12] videobuf2: let user-space know if driver
 supports cache hints

On 2/4/20 3:56 AM, Sergey Senozhatsky wrote:
> Add V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS to fill_buf_caps(), which
> is set when queue supports user-space cache management hints.

Ah, you add the capability here :-)

This should be moved forward in the series. Actually, I think this should
be merged with the first patch of the series.

Regards,

	Hans

> 
> Change-Id: Ieac93f3726c61fd3b88e02c36980c1f3c7a82ecc
> Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> ---
>  Documentation/media/uapi/v4l/vidioc-reqbufs.rst | 7 +++++++
>  drivers/media/common/videobuf2/videobuf2-v4l2.c | 2 ++
>  include/uapi/linux/videodev2.h                  | 1 +
>  3 files changed, 10 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> index 9741dac0d5b3..80603f57eb8a 100644
> --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
> @@ -165,6 +165,13 @@ aborting or finishing any DMA in progress, an implicit
>        - Only valid for stateless decoders. If set, then userspace can set the
>          ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
>  	capture buffer until the OUTPUT timestamp changes.
> +    * - ``V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS``
> +      - 0x00000040
> +      - Set when the queue/buffer support memory consistency and cache
> +        management hints. See :ref:`V4L2_FLAG_MEMORY_NON_CONSISTENT`,
> +        :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE` and
> +        :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN`.
> +
>  
>  Return Value
>  ============
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index eb5d1306cb03..22ae0ff64684 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -698,6 +698,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
>  	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
> +	if (q->allow_cache_hints)
> +		*caps |= V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS;
>  #ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
>  	if (q->supports_requests)
>  		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 169a8cf345ed..12b1bd220347 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -951,6 +951,7 @@ struct v4l2_requestbuffers {
>  #define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)
>  #define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)
>  #define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)
> +#define V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS		(1 << 6)
>  
>  /**
>   * struct v4l2_plane - plane info for multi-planar buffers
>