linux-kernel - Re: [RFC PATCH] media/doc: Allow sizeimage to be set by v4l clients

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <299e8aeb-6deb-b383-8f63-cf2cbf5d2e9f@xs4all.nl>
Date:   Fri, 18 Jan 2019 10:13:43 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        linux-media@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Vikash Garodia <vgarodia@...eaurora.org>,
        Tomasz Figa <tfiga@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>,
        Malathi Gottam <mgottam@...eaurora.org>
Subject: Re: [RFC PATCH] media/doc: Allow sizeimage to be set by v4l clients

On 1/16/19 1:37 PM, Stanimir Varbanov wrote:
> This changes v4l2_pix_format and v4l2_plane_pix_format sizeimage
> field description to allow v4l clients to set bigger image size
> in case of variable length compressed data.
> 
> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
> ---
>  Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst | 5 ++++-
>  Documentation/media/uapi/v4l/pixfmt-v4l2.rst        | 3 ++-
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst
> index 7f82dad9013a..dbe0b74e9ba4 100644
> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst
> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2-mplane.rst
> @@ -30,7 +30,10 @@ describing all planes of that format.
>  
>      * - __u32
>        - ``sizeimage``
> -      - Maximum size in bytes required for image data in this plane.
> +      - Maximum size in bytes required for image data in this plane,
> +        set by the driver. When the image consists of variable length
> +        compressed data this is the maximum number of bytes required
> +        to hold an image, and it is allowed to be set by the client.
>      * - __u32
>        - ``bytesperline``
>        - Distance in bytes between the leftmost pixels in two adjacent
> diff --git a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst
> index 71eebfc6d853..54b6d2b67bd7 100644
> --- a/Documentation/media/uapi/v4l/pixfmt-v4l2.rst
> +++ b/Documentation/media/uapi/v4l/pixfmt-v4l2.rst
> @@ -89,7 +89,8 @@ Single-planar format structure
>        - Size in bytes of the buffer to hold a complete image, set by the
>  	driver. Usually this is ``bytesperline`` times ``height``. When
>  	the image consists of variable length compressed data this is the
> -	maximum number of bytes required to hold an image.
> +	maximum number of bytes required to hold an image, and it is
> +	allowed to be set by the client.
>      * - __u32
>        - ``colorspace``
>        - Image colorspace, from enum :c:type:`v4l2_colorspace`.
> 

Hmm. "maximum number of bytes required to hold an image": that's not actually true
for bitstream formats like MPEG. It's just the size of the buffer used to store the
bitstream, i.e. one buffer may actually contain multiple compressed images, or a
compressed image is split over multiple buffers.

Only for MJPEG is this statement true since each buffer will contain a single
compressed JPEG image.

Regards,

	Hans