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Date: Mon, 12 Oct 2015 18:10:18 +0100
From: Mark Rutland <mark.rutland@arm.com>
To: Chen-Yu Tsai <wens@csie.org>
Cc: Hans de Goede <hdegoede@redhat.com>,
        Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
        Ian Campbell <ijc+devicetree@hellion.org.uk>,
        Kumar Gala <galak@codeaurora.org>,
        Maxime Ripard <maxime.ripard@free-electrons.com>,
        linux-fbdev@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Mark Brown <broonie@kernel.org>
Subject: Re: [PATCH RFC 1/2] dt-bindings: simplefb: Support a list of
 regulator supply properties
Message-ID: <20151012171018.GB3659@leverpostej>
References: <1444669458-5588-1-git-send-email-wens@csie.org>
 <1444669458-5588-2-git-send-email-wens@csie.org>
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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...

> Signed-off-by: Chen-Yu Tsai <wens@csie.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?

Thanks,
Mark.