Re: [PATCH v2 2/2] backlight: lm3630a: add an enable gpio for the HWEN pin

[Andreas Kemnade]

On Wed, 11 Sep 2019 13:48:36 -0500
Dan Murphy <dmurphy@xxxxxx> wrote:


> >> @@ -535,6 +538,13 @@ static int lm3630a_probe(struct i2c_client *client,
> >>   	}
> >>   	pchip->pdata = pdata;
> >>   
> >> +	pchip->enable_gpio = devm_gpiod_get_optional(&client->dev, "enable",
> >> +						GPIOD_OUT_HIGH);
> >> +	if (IS_ERR(pchip->enable_gpio)) {
> >> +		rval = PTR_ERR(pchip->enable_gpio);
> >> +		return rval;  
> 
> 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.
 
> Also on driver removal did you want to set the GPIO to low to disable 
> the device to save power?
> 
page 5 of the datasheet says:

Ishdn = Typ. 1ÂA max. 4ÂA.
For HWEN=Vin, I2c shutdown  (I guess this means outputs powered off)
ond for HWEN=GND.

So are we really saving something here?

Regards,
Andreas