[PATCH v2] Documentation: gpu: Mention the requirements for new properties

[Maxime Ripard <maxime@cerno.tech>]

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.

Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Alison Wang <alison.wang@nxp.com>
Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc: Andrew Jeffery <andrew@aj.id.au>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Anitha Chrisanthus <anitha.chrisanthus@intel.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Boris Brezillon <bbrezillon@kernel.org>
Cc: Brian Starkey <brian.starkey@arm.com>
Cc: Chen Feng <puck.chen@hisilicon.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Chun-Kuang Hu <chunkuang.hu@kernel.org>
Cc: Edmund Dea <edmund.j.dea@intel.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: "Heiko Stübner" <heiko@sntech.de>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Hyun Kwon <hyun.kwon@xilinx.com>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jernej Skrabec <jernej.skrabec@siol.net>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Cc: Joel Stanley <joel@jms.id.au>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Jonathan Hunter <jonathanh@nvidia.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Joonyoung Shim <jy0922.shim@samsung.com>
Cc: Jyri Sarha <jyri.sarha@iki.fi>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: "Noralf Trønnes" <noralf@tronnes.org>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: Paul Cercueil <paul@crapouillou.net>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Philippe Cornu <philippe.cornu@foss.st.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Qiang Yu <yuq825@gmail.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Sandy Huang <hjc@rock-chips.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Sean Paul <sean@poorly.run>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Steven Price <steven.price@arm.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Tian Tao <tiantao6@hisilicon.com>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Tomi Valkeinen <tomba@kernel.org>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Xinliang Liu <xinliang.liu@linaro.org>
Cc: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Cc: Yannick Fertre <yannick.fertre@foss.st.com>
Cc: Zack Rusin <zackr@vmware.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>

---

Changes from v2:
  - Typos and wording reported by Daniel and Alex
---
 Documentation/gpu/drm-kms.rst | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst
index 87e5023e3f55..c28b464dd397 100644
--- a/Documentation/gpu/drm-kms.rst
+++ b/Documentation/gpu/drm-kms.rst
@@ -463,6 +463,25 @@ 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 how 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.
+
+- 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.
+
+- An IGT test must be submitted where reasonable.
+
 Property Types and Blob Property Support
 ----------------------------------------
 
-- 
2.31.1