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Date:   Tue, 11 May 2021 19:16:28 +0200
From:   Daniel Vetter <daniel@ffwll.ch>
To:     Maxime Ripard <maxime@cerno.tech>
Cc:     dri-devel@lists.freedesktop.org,
        Daniel Vetter <daniel.vetter@intel.com>,
        David Airlie <airlied@linux.ie>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH] Documentation: gpu: Mention the requirements for new
 properties
Message-ID: <YJq77Kep8aTJxSdh@phenom.ffwll.local>
Mail-Followup-To: Maxime Ripard <maxime@cerno.tech>,
        dri-devel@lists.freedesktop.org,
        Daniel Vetter <daniel.vetter@intel.com>,
        David Airlie <airlied@linux.ie>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Thomas Zimmermann <tzimmermann@suse.de>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>
References: <20210511155512.582798-1-maxime@cerno.tech>
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On Tue, May 11, 2021 at 05:55:12PM +0200, Maxime Ripard wrote:
> New KMS properties come with a bunch of requirements to avoid each
> driver from running their own, inconsistent, set of properties,
> eventually leading to issues like property conflicts, inconsistencies
> between drivers and semantics, etc.
> 
> Let's document what we expect.
> 
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
>  Documentation/gpu/drm-kms.rst | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst
> index 87e5023e3f55..30f4c376f419 100644
> --- a/Documentation/gpu/drm-kms.rst
> +++ b/Documentation/gpu/drm-kms.rst
> @@ -463,6 +463,24 @@ KMS Properties
>  This section of the documentation is primarily aimed at user-space developers.
>  For the driver APIs, see the other sections.
>  
> +Requirements
> +------------
> +
> +KMS drivers might need to add extra properties to support new features.
> +Each new property introduced in a driver need to meet a few
> +requirements, in addition to the one mentioned above.:
> +
> +- It must be standardized, with some documentation to describe the
> +  property can be used.
> +
> +- It must provide a generic helper in the core code to register that
> +  property on the object it attaches to.

Maybe also include anything that drivers might want to precompute, e.g. we
have helpers for cliprects.

> +
> +- Its content must be decoded by the core and provided in the object

								object's
> +  associated state structure.
> +
> +- An IGT test must be submitted.

				"... where reasonable."

We have that disclaimer already here:

https://dri.freedesktop.org/docs/drm/gpu/drm-uapi.html#testing-requirements-for-userspace-api

I think would be good to cross-reference the uapi rules in general

https://dri.freedesktop.org/docs/drm/gpu/drm-uapi.html#open-source-userspace-requirements

With the bikesheds addressed:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

But this needs ideally a pile of acks from most display driver teams.
-Daniel

> +
>  Property Types and Blob Property Support
>  ----------------------------------------
>  
> -- 
> 2.31.1
> 

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