[PATCH v6] Documentation: gpu: Mention the requirements for new properties

* [PATCH v6] Documentation: gpu: Mention the requirements for new properties
@ 2021-07-20 14:35 Maxime Ripard
  2021-07-23 11:52 ` Maxime Ripard
  0 siblings, 1 reply; 2+ messages in thread
From: Maxime Ripard @ 2021-07-20 14:35 UTC (permalink / raw)
  To: dri-devel, Daniel Vetter, David Airlie, Maarten Lankhorst,
	Thomas Zimmermann, Maxime Ripard
  Cc: Xinliang Liu, Anitha Chrisanthus, Jonathan Hunter, Jerome Brunet,
	Kevin Hilman, Ludovic Desroches, NXP Linux Team, Sascha Hauer,
	Roland Scheidegger, Sean Paul, Hyun Kwon, Andrew Jeffery,
	Seung-Woo Kim, Noralf Trønnes, Pengutronix Kernel Team,
	Alex Deucher, Laurent Pinchart, Alexandre Belloni, linux-doc,
	Edmund Dea, Eric Anholt, Thierry Reding, Krzysztof Kozlowski,
	Steven Price, VMware Graphics, Ben Skeggs, Martin Blumenstingl,
	Rodrigo Siqueira, Boris Brezillon, Sandy Huang, Kyungmin Park,
	Maxime Coquelin, Haneen Mohammed, Neil Armstrong, Melissa Wen,
	Gerd Hoffmann, Benjamin Gaignard, Sam Ravnborg, Jonathan Corbet,
	Xinwei Kong, Chen-Yu Tsai, Alyssa Rosenzweig, Chun-Kuang Hu,
	Jonas Karlman, Chen Feng, Alison Wang, Rodrigo Vivi,
	Tomeu Vizoso, Tomi Valkeinen, Kieran Bingham, Tian Tao,
	Shawn Guo, Christian König, Daniel Vetter, Liviu Dudau,
	Alexandre Torgue, Paul Cercueil, Andrzej Hajda, Huang Rui,
	Marek Vasut, Joonyoung Shim, Oleksandr Andrushchenko,
	Russell King, Philippe Cornu, Hans de Goede, Matthias Brugger,
	Jernej Skrabec, Pekka Paalanen, Yannick Fertre, Nicolas Ferre,
	Robert Foss, Qiang Yu, Jyri Sarha

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: 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: Pekka Paalanen <pekka.paalanen@collabora.com>
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: Simon Ser <contact@emersion.fr>
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: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>

---

Changes from v5:
  - Typos fixes suggested by Pekka and Daniel
  - Added Pekka Reviewed-by

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 | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Documentation/gpu/drm-kms.rst b/Documentation/gpu/drm-kms.rst
index 87e5023e3f55..12e25119e563 100644
--- a/Documentation/gpu/drm-kms.rst
+++ b/Documentation/gpu/drm-kms.rst
@@ -463,6 +463,35 @@ 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 needs 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 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 struct 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.
+
+* An IGT test must be submitted where reasonable.
+
 Property Types and Blob Property Support
 ----------------------------------------
 
-- 
2.31.1


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