Re: [RFC 2/3] drm/panel: Add simple panel support

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 08/30/2013 01:24 PM, Kumar Gala wrote:
> 
> On Aug 30, 2013, at 10:25 AM, Thierry Reding wrote:
> 
>> Add a driver for simple panels. Such panels can have a regulator that
>> provides the supply voltage and a separate GPIO to enable the panel.
>> Optionally the panels can have a backlight associated with them so it
>> can be enabled or disabled according to the panel's power management
>> mode.
>>
>> Support is added for three panels: An AU Optronics 10.1" WSVGA, a
>> Chunghwa Picture Tubes 10.1" WXGA and a Panasonic 10.1 WUXGA TFT LCD
>> panel.

>> diff --git a/Documentation/devicetree/bindings/panel/panel-simple.txt b/Documentation/devicetree/bindings/panel/panel-simple.txt

>> +Required properties:
>> +- compatible: should be one of:
>> +  - "auo,b101aw03": AU Optronics Corporation 10.1" WSVGA TFT LCD panel
>> +  - "cptt,claa101wb03": Chunghwa Picture Tubes Ltd. 10.1" WXGA TFT LCD panel
>> +  - "pc,vvx10f004b00": Panasonic Corporation 10.1" WUXGA TFT LCD panel
>> +
> 
> It would seem there should be a more generic compatible to cover the basic "panel-simple" case.

I would suggest only documenting "simple-panel" here, and not
documenting the specific panels at all; the panel-specific compatible
values would show up simply due to the rule that all compatible values
in *.dts should contain the exact HW model (e.g. "auo,b101aw03"), plus
any HW they're compatible with (i.e. "simple-panel").

I'd suggest "simple-panel" rather than "panel-simple" since IIRC other
simple bindings are "simple-xxx" rather than "xxx-simple".

>> +Optional properties:
>> +- ddc-i2c-bus: phandle of an I2C controller used for DDC EDID probing
>> +- power-supply: regulator to provide the supply voltage
>> +- enable-gpios: GPIO pin to enable or disable the panel
>> +- backlight: phandle of the backlight device attached to the panel
>> +
> 
> If these are all optional, what does it mean to be a "panel-simple"?

I think at least ddc-i2c-bus and backlight should be required
properties. I suppose it might be possible for the panel to be
always-on, and hence enable-gpios/power-supply could be optional?