Re: [PATCH v3 3/6] drm/modes: Allow to specify rotation and reflection on the commandline

From: Maxime Ripard <maxime.ripard@bootlin.com>
To: "Noralf Trønnes" <noralf@tronnes.org>
Cc: eben@raspberrypi.org, David Airlie <airlied@linux.ie>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	dri-devel@lists.freedesktop.org,
	Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
	Sean Paul <seanpaul@chromium.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Daniel Vetter <daniel.vetter@intel.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 3/6] drm/modes: Allow to specify rotation and reflection on the commandline
Date: Thu, 13 Jun 2019 14:50:24 +0200	[thread overview]
Message-ID: <20190613125024.46yiiy6zrrqojajy@flea> (raw)
In-Reply-To: <c73e9c29-e20b-65e0-553c-67b9c2cd349a@tronnes.org>

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Hi,

On Wed, Jun 12, 2019 at 03:21:19PM +0200, Noralf Trønnes wrote:
> >> The only way I see for that to happen, is to set
> >> ->panel_orientation. And to repeat myself, imo that makes
> >> 'orientation' a better name for this video= option.
> >
> > orientation and rotation are two different things to me. The
> > orientation of a panel for example is absolute, while the rotation is
> > a transformation. In this particular case, I think that both the
> > orientation and the rotation should be taken into account, with the
> > orientation being the default state, and the hardware / panel will
> > tell us that, while the rotation would be a transformation from that
> > default to whatever the user wants.
> >
> > More importantly, the orientation is a property of the hardware (ie,
> > how the display has been assembled), while the rotation is a software
> > construct.
> >
> > And if the property being used to expose that is the rotation, I guess
> > it would make sense to just use the same name and remain consistent.
>
> Ok, I see. Based on this, I would assume that rotation would be relative
> to the orientation, but I see that in this patch rotation doesn't take
> orintation into account, it just overwrites it.

Yeah, that's a good point. I've updated the next version to add the
rotation on the command line to the orientation.

> I don't how userspace deals with rotation on top of orientation.

The orientation is exposed through the property, and the result is
available through the plane's rotation, so I guess that it's enough?

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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