linux-kernel - Re: [PATCH v4 2/5] drm/drm_property: require DRM_MODE_PROP

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Message-ID: <20240717-bouncy-horned-mamba-5691b8@houat>
Date: Wed, 17 Jul 2024 15:42:46 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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Subject: Re: [PATCH v4 2/5] drm/drm_property: require DRM_MODE_PROP_IMMUTABLE
 for single-value props

Hi,

On Mon, Jul 15, 2024 at 09:33:02AM GMT, Dmitry Baryshkov wrote:
> Document that DRM_MODE_PROP_IMMUTABLE must be set for the properties
> that are immutable by definition - e.g. ranges with min == max or enums
> with a single value. This matches the behaviour of the IGT tests, see
> kms_properties.c / validate_range_prop(), validate_enum_prop(),
> validate_bitmask_prop().
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

We had a discussion yesterday about it on IRC with Sima, Simon and
Xaver.

https://oftc.irclog.whitequark.org/dri-devel/2024-07-16#33374622;

The conclusion was that it would create an inconsistency between drivers
on whether a given property is immutable or not, which will lead to more
troubles for userspace.

It's not clear why Ville added that check in the first place, so the
best course of action is to remove the IGT test and get the discussion
started there.

Maxime

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