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

[Maxime Ripard]

Hi Noralf,

On Fri, Apr 19, 2019 at 10:53:28AM +0200, Noralf Trønnes wrote:
> Den 18.04.2019 18.40, skrev Noralf Trønnes:
> >
> >
> > Den 18.04.2019 14.41, skrev Maxime Ripard:
> >> Rotations and reflections setup are needed in some scenarios to initialise
> >> properly the initial framebuffer. Some drivers already had a bunch of
> >> quirks to deal with this, such as either a private kernel command line
> >> parameter (omapdss) or on the device tree (various panels).
> >>
> >> In order to accomodate this, let's create a video mode parameter to deal
> >> with the rotation and reflexion.
> >>
> >> Signed-off-by: Maxime Ripard <maxime.ripard at bootlin.com>
> >> ---
> >>  drivers/gpu/drm/drm_client_modeset.c |  10 +++-
> >>  drivers/gpu/drm/drm_modes.c          | 110 ++++++++++++++++++++++------
> >>  include/drm/drm_connector.h          |   9 ++-
> >>  3 files changed, 109 insertions(+), 20 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c
> >> index f2869c82510c..15145d2c86d5 100644
> >> --- a/drivers/gpu/drm/drm_client_modeset.c
> >> +++ b/drivers/gpu/drm/drm_client_modeset.c
> >> @@ -823,6 +823,7 @@ EXPORT_SYMBOL(drm_client_modeset_probe);
> >>  bool drm_client_panel_rotation(struct drm_mode_set *modeset, unsigned int *rotation)
> >>  {
> >>  	struct drm_connector *connector = modeset->connectors[0];
> >> +	struct drm_cmdline_mode *cmdline;
> >>  	struct drm_plane *plane = modeset->crtc->primary;
> >>  	u64 valid_mask = 0;
> >>  	unsigned int i;
> >> @@ -844,6 +845,15 @@ bool drm_client_panel_rotation(struct drm_mode_set *modeset, unsigned int *rotat
> >>  		*rotation = DRM_MODE_ROTATE_0;
> >>  	}
> >>
> >> +	/**
> >> +	 * We want the rotation on the command line to overwrite
> >> +	 * whatever comes from the panel.
> >> +	 */
> >> +	cmdline = &connector->cmdline_mode;
> >> +	if (cmdline->specified &&
> >> +	    cmdline->rotation != DRM_MODE_ROTATE_0)
> >
> > I believe you need to drop that second check, otherwise rotate=0 will
> > not overwrite panel rotation.
> >
> >> +		*rotation = cmdline->rotation;
>
> I remembered that you wanted this to propagate to DRM userspace. That's
> not happening here.

It's propated to the userspace through the plane's rotation property,
I just checked.

> 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.

Maxime

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