linux-kernel - Re: [PATCH v3,04/21] v4l: add documentation for secure memory flag

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Date:   Mon, 11 Dec 2023 12:05:27 +0100
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Yunfei Dong <yunfei.dong@...iatek.com>,
        Jeffrey Kardatzke <jkardatzke@...gle.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Nathan Hebert <nhebert@...omium.org>
Cc:     Chen-Yu Tsai <wenst@...omium.org>, Yong Wu <yong.wu@...iatek.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Fritz Koenig <frkoenig@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Steve Cho <stevecho@...omium.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Brian Starkey <Brian.Starkey@....com>,
        John Stultz <jstultz@...gle.com>,
        "T . J . Mercier" <tjmercier@...gle.com>,
        Christian König <christian.koenig@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v3,04/21] v4l: add documentation for secure memory flag

On 06/12/2023 09:15, Yunfei Dong wrote:
> From: Jeffrey Kardatzke <jkardatzke@...gle.com>
> 
> Adds documentation for V4L2_MEMORY_FLAG_SECURE.
> 
> Signed-off-by: Jeffrey Kardatzke <jkardatzke@...gle.com>
> Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
> ---
>  Documentation/userspace-api/media/v4l/buffer.rst | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst
> index 52bbee81c080..a5a7d1c72d53 100644
> --- a/Documentation/userspace-api/media/v4l/buffer.rst
> +++ b/Documentation/userspace-api/media/v4l/buffer.rst
> @@ -696,7 +696,7 @@ enum v4l2_memory
>  
>  .. _memory-flags:
>  
> -Memory Consistency Flags
> +Memory Flags
>  ------------------------
>  
>  .. raw:: latex
> @@ -728,6 +728,12 @@ Memory Consistency Flags
>  	only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the
>  	queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
>  	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
> +    * .. _`V4L2-MEMORY-FLAG-SECURE`:
> +
> +      - ``V4L2_MEMORY_FLAG_SECURE``
> +      - 0x00000002
> +      - DMA bufs passed into the queue will be validated to ensure they were
> +	allocated from a secure dma-heap.

Hmm, that needs a bit more work. How about:

- The queued buffers are expected to be in secure memory. If not, an error will be
  returned. This flag can only be used with ``V4L2_MEMORY_DMABUF``. Typically
  secure buffers are allocated using a secure dma-heap. This flag can only be
  specified if the ``V4L2_BUF_CAP_SUPPORTS_SECURE_MEM`` is set.

In addition, the title of this table is currently "Memory Consistency Flags": that
should be renamed to "Memory Flags".

Regards,

	Hans

>  
>  .. raw:: latex
>