linux-kernel - Re: [RESEND PATCH] drm/doc: Clarify what ioctls can be used on render nodes

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Date:   Thu, 17 Mar 2022 10:36:55 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Jeffrey Hugo <quic_jhugo@...cinc.com>
Cc:     maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...ux.ie, daniel@...ll.ch,
        corbet@....net, pekka.paalanen@...labora.com,
        dri-devel@...ts.freedesktop.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] drm/doc: Clarify what ioctls can be used on
 render nodes

On Mon, Mar 07, 2022 at 08:32:36AM -0700, Jeffrey Hugo wrote:
> The documentation for render nodes indicates that only "PRIME-related"
> ioctls are valid on render nodes, but the documentation does not clarify
> what that means.  If the reader is not familiar with PRIME, they may
> beleive this to be only the ioctls with "PRIME" in the name and not other
> ioctls such as set of syncobj ioctls.  Clarify the situation for the
> reader by referencing where the reader will find a current list of valid
> ioctls.
> 
> Signed-off-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
> Acked-by: Pekka Paalanen <pekka.paalanen@...labora.com>

Applied to drm-misc-next, thanks for the patch.
-Daniel

> ---
> 
> I was confused by this when reading the documentation.  Now that I have
> figured out what the documentation means, I would like to add a clarification
> for the next reader which would have helped me.
> 
>  Documentation/gpu/drm-uapi.rst | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst
> index 199afb5..ce47b42 100644
> --- a/Documentation/gpu/drm-uapi.rst
> +++ b/Documentation/gpu/drm-uapi.rst
> @@ -148,7 +148,9 @@ clients together with the legacy drmAuth authentication procedure.
>  If a driver advertises render node support, DRM core will create a
>  separate render node called renderD<num>. There will be one render node
>  per device. No ioctls except PRIME-related ioctls will be allowed on
> -this node. Especially GEM_OPEN will be explicitly prohibited. Render
> +this node. Especially GEM_OPEN will be explicitly prohibited. For a
> +complete list of driver-independent ioctls that can be used on render
> +nodes, see the ioctls marked DRM_RENDER_ALLOW in drm_ioctl.c  Render
>  nodes are designed to avoid the buffer-leaks, which occur if clients
>  guess the flink names or mmap offsets on the legacy interface.
>  Additionally to this basic interface, drivers must mark their
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch