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

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Date:	Tue, 13 Oct 2015 09:08:46 +0200
From:	Hans de Goede <hdegoede@...hat.com>
To:	Chen-Yu Tsai <wens@...e.org>, Mark Rutland <mark.rutland@....com>
Cc:	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

Hi,

On 13-10-15 04:22, Chen-Yu Tsai wrote:
> 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?

+1 for this.

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

I would not add a hard limit to the binding, you can use a fixed array in
the code to make the code simpler. I would say 8 should be sufficient, since
the limit will only be in the code we can always bump it when we need to.

Regards,

Hans
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