linux-kernel - Re: [PATCH 3/4] [media] ad5820: DT new optional field enable-gpios

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Date:   Thu, 20 Sep 2018 23:21:28 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:     Pavel Machek <pavel@....cz>, Sakari Ailus <sakari.ailus@....fi>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hans Verkuil <hans.verkuil@...co.com>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 3/4] [media] ad5820: DT new optional field enable-gpios

Hi Ricardo,

Thank you for the patch.

On Thursday, 20 September 2018 19:19:11 EEST Ricardo Ribalda Delgado wrote:
> Document new enable-gpio field. It can be used to disable the part
> without turning down its regulator.
> 
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
> ---
>  Documentation/devicetree/bindings/media/i2c/ad5820.txt | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> b/Documentation/devicetree/bindings/media/i2c/ad5820.txt index
> 5940ca11c021..07d577bb37f7 100644
> --- a/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> +++ b/Documentation/devicetree/bindings/media/i2c/ad5820.txt
> @@ -8,6 +8,11 @@ Required Properties:
> 
>    - VANA-supply: supply of voltage for VANA pin
> 
> +Optional properties:
> +
> +   - enable-gpios : GPIO spec for the XSHUTDOWN pin.

xshutdown is active-low, so enable is active-high. Should this be documented 
explicitly, to avoid polarity errors ? Maybe something along the lines of

- enable-gpios: GPIO spec for the XSHUTDOWN pin. Note that the polarity of the 
enable GPIO is the opposite of the XSHUTDOWN pin (asserting the enable GPIO 
deasserts the XSHUTDOWN signal and vice versa).

> If specified, it will be
> +     asserted when VANA-supply is enabled.

That documents a driver behaviour, is it needed in DT ?


>  Example:
> 
>         ad5820: coil@c {
> @@ -15,5 +20,6 @@ Example:
>                 reg = <0x0c>;
> 
>                 VANA-supply = <&vaux4>;
> +               enable-gpios = <&msmgpio 26 GPIO_ACTIVE_HIGH>;
>         };

-- 
Regards,

Laurent Pinchart