linux-kernel - Re: [PATCH v10 3/6] media: platform: synopsys: Add support for HDMI input driver

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Message-ID: <3872267b32d1386827635f15eda99d2709b44a96.camel@collabora.com>
Date: Thu, 27 Feb 2025 14:40:06 -0500
From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
To: Dmitry Osipenko <dmitry.osipenko@...labora.com>, Diederik de Haas	
 <didi.debian@...ow.org>, Shreeya Patel <shreeya.patel@...labora.com>, Heiko
 Stuebner <heiko@...ech.de>, Mauro Carvalho Chehab <mchehab@...nel.org>,
 Hans Verkuil	 <hverkuil@...all.nl>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski	 <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, 	jose.abreu@...opsys.com, nelson.costa@...opsys.com,
 shawn.wen@...k-chips.com,  Sebastian Reichel
 <sebastian.reichel@...labora.com>
Cc: kernel@...labora.com, linux-media@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-rockchip@...ts.infradead.org, Tim Surber <me@...surber.de>,
 Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: Re: [PATCH v10 3/6] media: platform: synopsys: Add support for HDMI
 input driver

Le jeudi 27 février 2025 à 08:28 +0300, Dmitry Osipenko a écrit :
> On 2/26/25 18:14, Diederik de Haas wrote:
> > > +config VIDEO_SYNOPSYS_HDMIRX_LOAD_DEFAULT_EDID
> > > +	bool "Load default EDID"
> > > +	depends on VIDEO_SYNOPSYS_HDMIRX
> > > +	help
> > > +	  Preload default EDID (Extended Display Identification Data).
> > I see some value in making explicit what you mean by EDID ...
> > 
> > > +	  EDID contains information about the capabilities of the display,
> > > +	  such as supported resolutions, refresh rates, and audio formats.
> > ... I do not think a/this Kconfig needs to explain it.
> > 
> > > +
> > > +	  Enabling this option is recommended for a non-production use-cases.
> > My guess is that it could be useful for development/debugging/CI work
> > which possibly do not have an actual device (monitor) which provides
> > actual EDID data? Is CI work the reason why you (initially) enabled it
> > in the defconfig?
> > But when you have an actual monitor (=production use-case?), you
> > (really) do not want it? Would it be harmless if 'still' enabled?
> 
> Disabling this option is only relevant if you're making a commercial
> product using this driver. It's a quite widespread issue that HDMI
> projectors utilize default EDID that comes from BSP driver they use,
> while a rebrand EDID should be used. Keeping this option enabled is
> harmless, but you don't want to do it in a product.
> 
> For all other use-cases you would want to enable this option, otherwise
> driver won't be usable until you will load EDID from userspace.
> 
> Hans has strong opinion RE this option and wants to have it disabled by
> default.

Hans, can you detail your reasons ? We personally make default config
toward generic Linux distributions. If you don't turn this on, the
driver won't work with any existing userspace (OBS, GStreamer, Web
browsers, etc). While having it disabled, to avoid not having your
brand or specific choices on the first go is clearly the "specialized"
usage and configuration.

> 
> > Thus a more extensive description what this Kconfig item does and why
> > and when I want to enable it or not, seems more useful to me.
> 
> Will update and expand the description with more clarification. Thanks
> for suggestion.
> 

regards,

-- 
Nicolas Dufresne
Principal Engineer at Collabora