[Intel-gfx] [PATCH 1/2] gpio/crystalcove: Export Panel and backlight en/disable signals as GPIO

[Linus Walleij]

On Wed, Feb 18, 2015 at 1:18 PM, Shobhit Kumar <shobhit.kumar at intel.com> wrote:

> Export Panel BACKLIGHT_EN(offset 0x51) and PANEL_EN(offset 0x52) as two
> additional GPIOs. Needed by display driver to enable the DSI panel on
> BYT platform where the Panel EN/Disable and Backlight control are
> routed thorugh CRC PMIC
>
> Cc: Linus Walleij <linus.walleij at linaro.org>
> Cc: Alexandre Courbot <gnurou at gmail.com>
> Cc: Thierry Reding <thierry.reding at gmail.com>
> Signed-off-by: Shobhit Kumar <shobhit.kumar at intel.com>

This seems very unintuitive. I have a hard time believeing this:

> +#define GPIOPANELCTL           0x51

A special GPIO only designated to panel control? That is totally
counter to the *meaning* of "general purpose input/output".
It is not general purpose at all, it is special-purpose.

If the data sheet says a special-purpose pin is a "GPIO" when
it isn't the map of the world (the datasheet terminology) is wrong,
not the world, the usage is dedicated for the panel. Look
at the usecase, not the name.

Obviously that line is only for controlling the backlight, and you
should spin a new child device from the Inte SoC PMIC MFD hub
and put a driver for it in drivers/video/backlight or wherever this
goes.

Lee: do you agree?

Yours,
Linus Walleij