Re: [PATCH v3] Documentation: gpu: Mention the requirements for new properties

[Maxime Ripard <maxime@cerno.tech>]

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Hi,

On Thu, Jun 10, 2021 at 11:00:05PM +0200, Daniel Vetter wrote:
> On Thu, Jun 10, 2021 at 7:47 PM Maxime Ripard <maxime@cerno.tech> 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.
> >
> > 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:
> >   - Take into account the feedback from Laurent and Lidiu to no longer
> >     force generic properties, but prefix vendor-specific properties with
> >     the vendor name
> 
> I'm pretty sure my r-b was without this ...

Yeah, sorry. I wanted to tell you on IRC that you wanted to have a
second look, but I shouldn't have kept it and caught you by surprise
indeed.

> Why exactly do we need this? KMS is meant to be fairly generic (bugs
> throw a wrench around here sometimes, and semantics can be tricky). If
> we open up the door to yolo vendor properties in upstream, then that
> goal is pretty much written off. And we've been there with vendor
> properties, it's a giantic mess.
> 
> Minimally drop my r-b, I'm definitely not in support of this idea.

So the argument Lidiu and Laurent made was that in some cases, getting a
generic property right with only a couple of users is hard. So they
advocated for the right to keep non-generic properties. I can get the
argument, and no-one else said that was wrong, so it felt like the
consensus was there.

> If there's a strong consensus that we really need this then I'm not
> going to nack this, but this really needs a pile of acks from
> compositor folks that they're willing to live with the resulting
> fallout this will likely bring. Your cc list seems to have an absence
> of compositor folks, but instead every driver maintainer. That's
> backwards. We make uapi for userspace, not for kernel driver
> maintainers!

Right, but it's mostly about in-kernel rules though? And you're the one
who mentionned CC'ing the driver maintainers in the first iteration?

> ltdr; I'd go back to v2. And then cc compositor folks on this to get
> their ack.

So, Pekka, Simon, is there anyone else I should Cc?

Thanks!
Maxime

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