linux-kernel - Re: [PATCH RFC 1/2] dt-bindings: simplefb: Support a list of regulator supply properties

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Message-ID: <CAGb2v651=uaHEQK4wpEQywgr311NSbqEvYkpsC5zSHPSFq-HHg@mail.gmail.com>
Date:	Tue, 13 Oct 2015 10:22:39 +0800
From:	Chen-Yu Tsai <wens@...e.org>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Chen-Yu Tsai <wens@...e.org>, Hans de Goede <hdegoede@...hat.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	devicetree <devicetree@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH RFC 1/2] dt-bindings: simplefb: Support a list of
 regulator supply properties

On Tue, Oct 13, 2015 at 1:10 AM, Mark Rutland <mark.rutland@....com> wrote:
> On Tue, Oct 13, 2015 at 01:04:17AM +0800, Chen-Yu Tsai wrote:
>> 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.

>
>> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
>> ---
>>  .../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
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