On Tue, 6 Jul 2021 18:12:44 +0200 Maxime Ripard <maxime@xxxxxxxxxx> 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. ... > Changes from v4: > - Changes suggested by Pekka > > Changes from v3: > - Roll back to the v2 > - Add Simon and Pekka in Cc > > Changes from v2: > - Take into account the feedback from Laurent and Lidiu to no longer > force generic properties, but prefix vendor-specific properties with > the vendor name > > Changes from v1: > - Typos and wording reported by Daniel and Alex > --- > Documentation/gpu/drm-kms.rst | 30 ++++++++++++++++++++++++++++++ > 1 file changed, 30 insertions(+) > > diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst > index 87e5023e3f55..47994890fd1e 100644 > --- a/Documentation/gpu/drm-kms.rst > +++ b/Documentation/gpu/drm-kms.rst > @@ -463,6 +463,36 @@ 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, documenting: > + > + * The full, exact, name string; > + * If the property is an enum, all the valid variants name; Hi, "variant" feels a little off to me, I would have used "value name strings". > + * What values are accepted, and what these values mean; > + * What the property does and how it can be used; > + * How the property might interact with other, existing properties. > + > +* It must provide a generic helper in the core code to register that > + property on the object it attaches to. > + > +* Its content must be decoded by the core and provided in the object's > + associated state structure. That includes anything drivers might want > + to precompute, like :c:type:`struct drm_clip_rect <drm_clip_rect>` for > + planes. > + > +* Its initial state must match the behavior prior to the property > + introduction. This might be a fixed value matching what the hardware > + does, or it may be inherited from the state the firmware left the > + system in during boot. I'd like to point out that this rule should apply also to properties that already exist in general, but are newly exposed in a driver for hardware that didn't expose the property before. > + > +* An IGT test must be submitted where reasonable. > + > Property Types and Blob Property Support > ---------------------------------------- > Regardless of my comments above: Reviewed-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx> Thanks, pq
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