linux-kernel - Re: [PATCH 1/2] leds: Add control of the voltage/current regulator to the LED core

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Date:   Mon, 15 Jul 2019 16:19:35 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Jean-Jacques Hiblot <jjhiblot@...com>
Cc:     Dan Murphy <dmurphy@...com>, jacek.anaszewski@...il.com,
        pavel@....cz, robh+dt@...nel.org, mark.rutland@....com,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 1/2] leds: Add control of the voltage/current regulator
 to the LED core

On Mon, Jul 15, 2019 at 11:47:08AM +0200, Jean-Jacques Hiblot wrote:
> > > > > +    if (IS_ERR(led_cdev->regulator)) {
> > > > > +        dev_err(led_cdev->dev, "Cannot get the power supply for %s\n",
> > > > > +            led_cdev->name);
> > > > > +        device_unregister(led_cdev->dev);
> > > > > +        mutex_unlock(&led_cdev->led_access);
> > > > > +        return PTR_ERR(led_cdev->regulator);
> > > > This is listed as optional in the DT doc.  This appears to be required.
> > > The regulator core will provide a dummy regulator if none is given in the
> > > device tree. I would rather have an error in that case, but that is not how
> > > it works.
> > If you actively wanted to get -ENODEV back when there is no regulator
> > then you can use devm_regulator_get_optional() for that.
> > 
> > However perhaps be careful what you wish for. If you use get_optional()
> > then you will have to sprinkle NULL or IS_ERR() checks everywhere. I'd
> > favour using the current approach!
> 
> Thanks for the info. I think I'll use the get_optionnal(). That will add a
> bit of complexity, but it will avoid deferring some work in
> led_set_brightness_nopm() when it is not needed.

Makes sense, I didn't notice that it allows you to avoid deferred work.


Daniel.