On Tue, Oct 13, 2015 at 1:10 AM, Mark Rutland [off-list ref] wrote:

On Tue, Oct 13, 2015 at 01:04:17AM +0800, Chen-Yu Tsai wrote:

quoted

The physical display tied to the framebuffer may have regulators
providing power to it, such as power for LCDs or interface conversion
chips.

The number of regulators in use may vary, but the regulator supply
binding can not be a list. Work around this by adding a "num-supplies"
property to communicate the number of supplies, and a list of 0 ~ N
"vinN-supply" properties for the actual regulator supply.

This is getting more complicated by the minute...

Yeah...

I considered "backlight" and "panel" properties, but that seems to need
more effort to parse. Regulators seemed easier.

quoted

Signed-off-by: Chen-Yu Tsai <redacted>
---
 .../devicetree/bindings/video/simple-framebuffer.txt       | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/video/simple-framebuffer.txt b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
index 4474ef6e0b95..0cc43e1be8b5 100644
--- a/Documentation/devicetree/bindings/video/simple-framebuffer.txt
+++ b/Documentation/devicetree/bindings/video/simple-framebuffer.txt

@@ -47,10 +47,14 @@ Required properties:
   - a8b8g8r8 (32-bit pixels, d[31:24]=a, d[23:16]=b, d[15:8]=g, d[7:0]=r).

 Optional properties:
-- clocks : List of clocks used by the framebuffer. Clocks listed here
-           are expected to already be configured correctly. The OS must
-           ensure these clocks are not modified or disabled while the
-           simple framebuffer remains active.
+- clocks : List of clocks used by the framebuffer.
+- num-supplies : The number of regulators used by the framebuffer.
+- vinN-supply : The N-th (from 0) regulator used by the framebuffer.

I don't see why you need num-supplies. Why not just try probing
vin${N}-supply until such a property isn't present in the DT?

That's doable. Though I'd add a hard limit on it. Does 16 seem reasonable?

Thanks
ChenYu