[RFC PATCH 0/3] drm/panel: Support panel detection

[Boris Brezillon <boris.brezillon@bootlin.com>]

Some panels are connected through extension boards an provide an easy
way for the main board to detect when they are present (like checking
for a working I2C communication with a device and making sure a
specific reg in this device has a consistent value).

When this is the case, we might want to support dynamic panel detection
and only expose the display (and its display modes) when the panel is
detected, similar to the monitor detection we use for regular
connectors (HDMI, DVI, ...).

This solves a problem we have on the Rpi when the panel is not
connected to the board but described in the DT. This prevents the whole
display pipeline from being exposed because one of the element (the
panel) is missing.

This was posted as an RFC because I'm not sure dynamically detecting
panels or supporting panel hotplug is actually something we want to do.

Thierry, and DRM folks in general, feel free to give your opinion on
this approach, and/or propose others solution to solve the "DSI panel
not connected" problem we have on RPi. Oh, and before someone suggests
it, IIRC, Eric wanted to avoid relying on DT overlays to do that, I
don't remember why though.

Regards,

Boris

Boris Brezillon (3):
  drm/panel: Support panel detection
  drm/bridge: panel: Make use of the panel detection infrastructure
  drm/panel: rpi-touchscreen: Implement ->detect()

 drivers/gpu/drm/bridge/panel.c                     | 13 +++++
 .../gpu/drm/panel/panel-raspberrypi-touchscreen.c  | 62 ++++++++++++++++++----
 include/drm/drm_panel.h                            | 12 +++++
 3 files changed, 78 insertions(+), 9 deletions(-)

-- 
2.14.1

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