Re: [PATCH v2 2/2] leds: trigger: gpio: Convert to use kstrtox()

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Sun, Sep 01, 2019 at 12:23:17PM +0200, Pavel Machek wrote:
> On Fri 2019-08-30 18:08:20, Andy Shevchenko wrote:
> > sscanf() is a heavy one and moreover requires additional boundary checks.
> > Convert driver to use kstrtox() and replace kstrtoul() by kstrtobool()
> > in gpio_trig_inverted_store().
> > 
> > While here, check the desired brightness against maximum defined for
> > a certain LED.
> 
> One change per patch, please.
> 
> Because this one will not end well.
> 
> > @@ -60,10 +60,10 @@ static ssize_t gpio_trig_brightness_store(struct device *dev,
> >  	unsigned desired_brightness;
> >  	int ret;
> >  
> > -	ret = sscanf(buf, "%u", &desired_brightness);
> > -	if (ret < 1 || desired_brightness > 255) {
> > +	ret = kstrtouint(buf, 10, &desired_brightness);
> > +	if (ret || desired_brightness > gpio_data->led->max_brightness) {
> >  		dev_err(dev, "invalid value\n");
> > -		return -EINVAL;
> > +		return ret ? ret : -EINVAL;
> >  	}
> 
> We have people writing 255 into brightness, because that's what we
> used to do even for on/off LEDS. It is expected to work even for leds
> with max_brightness of 1.
> 
> So... we want to saturate here, not return -EINVAL. (And we will
> eventually want to switch on/off leds to max_brightness = 1...)

Agree. Thank you for your review!

> 
> > @@ -86,16 +86,13 @@ static ssize_t gpio_trig_inverted_store(struct device *dev,
> >  {
> >  	struct led_classdev *led = led_trigger_get_led(dev);
> >  	struct gpio_trig_data *gpio_data = led_trigger_get_drvdata(dev);
> > -	unsigned long inverted;
> > +	bool inverted;
> >  	int ret;
> >  
> > -	ret = kstrtoul(buf, 10, &inverted);
> > -	if (ret < 0)
> > +	ret = kstrtobool(buf, &inverted);
> > +	if (ret)
> >  		return ret;
> >  
> > -	if (inverted > 1)
> > -		return -EINVAL;
> > -
> >  	gpio_data->inverted = inverted;
> >  
> >  	/* After inverting, we need to update the LED. */
> 
> So, this accepted 0/1. Now it also accepts true false and many other pairs.
> 
> Which... might be ok. But probably should be separated.



-- 
With Best Regards,
Andy Shevchenko