[PATCH 0/3] fb/drm: Add support for a panel-orientation connector prop

[Daniel Vetter]

On Fri, Sep 08, 2017 at 01:54:41PM +0200, Hans de Goede wrote:
> Hi All,
> 
> Some x86 clamshell design devices use portrait tablet LCD panels and a
> display engine which cannot (transparently) rotate in hardware, so we
> need to rotate things in software / let user space deal with this.
> 
> The fbcon code has a set of DMI based quirks to automatically detect
> such tablet LCD panels and rotate the fbcon to compensate.
> 
> The plan was for userspace (e.g. a Wayland compositor) to simply read
> /sys/class/graphics/fbcon/rotate and apply the rotation from there to
> the LCD panel to compensate.
> 
> However this will not work when an external monitor gets plugged in,
> since with fbcon rotation is not per output, so the fbcon quirk code
> disables the rotation when an external monitor is present.

Hm, where is that handled? Afaiui the fbdev emulation in drm completel
hides that there's possibly multiple monitors connected, which means I
have no idea how fbcon can even figure this out. Can you give some
pointers to relevant code?

Thanks, Daniel

> 
> Using /sys/class/graphics/fbcon/rotate will not help in that case
> since it will indicate no rotation is in use. So instead we are going
> to need a drm connecter property for this.
> 
> This patch-series introduces such a drm connector properperty, it
> consists of 3 patches:
> 
> 1) Make the fbcon quirk table usable outside of the fbcon code
> 2) Add drm_connector_create_panel_orientation_property and
>    drm_connector_attach_panel_orientation_property functions
> 3) Hook things up in intel_panel.c
> 
> Regards,
> 
> Hans
> 
> 
> p.s.
> 
> Note this series does not yet get the panel orientation from the VBT
> on Intel devices. I think that for devices which have the panel
> upside-down (rather then rotated 90 degrees) this should work, but
> I've an i915 patch series pending which corrects for the upside-down
> scanario fully inside the i915 driver hiding the upside-down ness
> from userspace (and fbcon) and if that series gets merged then in
> the upside-down case the "panel orientation" property should read
> "Normal" and not "Upside Down", so I've left out hooking up the VBTs
> idea of the panel orientation for now.
> 
> Note that we could use the new "panel orientation" property for the
> upside-down case too and drop my "[v4] drm/i915: Deal with upside-down
> mounted LCD panels" patch:
> https://patchwork.freedesktop.org/patch/173781/
> 
> That patch is not universally liked anyways, so just dropping it and
> using the new prop this series introduces might be best.
>  
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch