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Date:   Wed, 11 Sep 2019 22:25:13 +0200
From:   Andreas Kemnade <andreas@kemnade.info>
To:     Dan Murphy <dmurphy@ti.com>
Cc:     Daniel Thompson <daniel.thompson@linaro.org>,
        <lee.jones@linaro.org>, <jingoohan1@gmail.com>,
        <jacek.anaszewski@gmail.com>, <pavel@ucw.cz>, <robh+dt@kernel.org>,
        <mark.rutland@arm.com>, <b.zolnierkie@samsung.com>,
        <dri-devel@lists.freedesktop.org>, <linux-leds@vger.kernel.org>,
        <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-fbdev@vger.kernel.org>,
        "H. Nikolaus Schaller" <hns@goldelico.com>
Subject: Re: [PATCH v2 2/2] backlight: lm3630a: add an enable gpio for the
 HWEN pin
Message-ID: <20190911222513.489b5235@aktux>
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        <a3f10318-11f4-3b78-47e5-d9add8a46791@ti.com>
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On Wed, 11 Sep 2019 13:48:36 -0500
Dan Murphy <dmurphy@ti.com> wrote:


> >> @@ -535,6 +538,13 @@ static int lm3630a_probe(struct i2c_client *clien=
t,
> >>   	}
> >>   	pchip->pdata =3D pdata;
> >>  =20
> >> +	pchip->enable_gpio =3D devm_gpiod_get_optional(&client->dev, "enable=
",
> >> +						GPIOD_OUT_HIGH);
> >> +	if (IS_ERR(pchip->enable_gpio)) {
> >> +		rval =3D PTR_ERR(pchip->enable_gpio);
> >> +		return rval; =20
>=20
> the enable gpio is optional so if it fails you log the error and move on
>
well, if the gpio is not there, then it returns NULL.
It might return e.g. -EDEFER. So I need to check for errors here.
=20
> Also on driver removal did you want to set the GPIO to low to disable=20
> the device to save power?
>=20
page 5 of the datasheet says:

Ishdn =3D Typ. 1=C2=B5A max. 4=C2=B5A.
For HWEN=3DVin, I2c shutdown  (I guess this means outputs powered off)
ond for HWEN=3DGND.

So are we really saving something here?

Regards,
Andreas