Re: [PATCH v2 1/3] devicetree/bindings: add reset-gpios and vcc-supply for panel-dpi

On 29/12/15 22:54, Rob Herring wrote:

On Sun, Dec 20, 2015 at 12:13:20PM +0100, Uwe Kleine-König wrote:

quoted

Some displays have a reset input and/or need a regulator to function
properly. Allow to specify them for panel-dpi devices.

Signed-off-by: Uwe Kleine-König <redacted>
---
 Documentation/devicetree/bindings/display/panel/panel-dpi.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/display/panel/panel-dpi.txt b/Documentation/devicetree/bindings/display/panel/panel-dpi.txt
index 216c894d4f99..b52ac52757df 100644
--- a/Documentation/devicetree/bindings/display/panel/panel-dpi.txt
+++ b/Documentation/devicetree/bindings/display/panel/panel-dpi.txt

@@ -7,6 +7,8 @@ Required properties:
 Optional properties:
 - label: a symbolic name for the panel
 - enable-gpios: panel enable gpio
+- reset-gpios: GPIO to control the RESET pin

The problem with this in a generic binding is what if the panel has 
ordering requirements like enable gpio has to be inactive when reset 
is deasserted?

quoted

+- vcc-supply: phandle of regulator that will be used to enable power to the display

What if there are 2 supplies?

Yes, I think it's an impossible task to create a really generic driver
wrt. gpios and supplies. There may be a bunch of them, and a particular
sequence to enable/disable needed, and even particular delays required
in between.

So I think the best we can do is to support (hopefully) most of the
panels by defining one sequence panel-dpi uses. If a particular panel
falls outside that, a separate driver is needed.

 Tomi