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

[Eric Anholt <eric@anholt.net>]

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Boris Brezillon <boris.brezillon@bootlin.com> writes:

> 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.

I want to clarify here: we're not trying to do panel hotplug.  We're
trying to boot-time-only detection of whether or not the standard panel
is plugged in.

Since this is something like the 6th variation of trying to get this
driver to work whether or not the panel is plugged in at boot, I'm
leaning toward just asking the closed source firmware to hack the DT to
add/remove the panel's node depending on whether it can probe it on I2C.
Relying on more closed source software in order to work around something
so trivial is really frustrating, though.

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