Re: [RESEND #2][PATCH] LEDS: Add output invertion option to backlight trigger

[Janusz Krzysztofik]

Saturday 02 October 2010 19:28:10 Lars-Peter Clausen wrote:
> Janusz Krzysztofik wrote:
> > This patch extends the LED backlight tirgger driver with an option that
> > allows for inverting the trigger output polarity.
> >
> > Whith the invertion option provided, I (ab)use the backlight trigger for
> > driving a led that indicates LCD display blank condtition on my Amstrad
> > Delta videophone. Since the machine has no dedicated power LED, it was
> > not possible to distinguish if its display was blanked or it was turned
> > off, without touching it.
> >
> > The invert sysfs control is modeled after a similiar function provided by
> > the gpio trigger driver.
> >
> > Created and tested against linux-2.6.35-rc3 on Amstrad Delta.
> > Re-tested against linux-2.6.36-rc5.
> >
> > Signed-off-by: Janusz Krzysztofik <jkrzyszt@xxxxxxxxxxxx>
> > ---
> >  drivers/leds/ledtrig-backlight.c |   59
> > ++++++++++++++++++++++++++++++++++++--- 1 file changed, 55 insertions(+),
> > 4 deletions(-)
> >
> > diff -uprN git/drivers/leds/ledtrig-backlight.c
> > git/drivers/leds/ledtrig-backlight.c ---
> > git/drivers/leds/ledtrig-backlight.c	2010-06-15 18:01:50.000000000 +0200
> > +++ git/drivers/leds/ledtrig-backlight.c	2010-06-23 02:48:44.000000000
> > +0200 @@ -26,6 +26,7 @@ struct bl_trig_notifier {
> >  	int brightness;
> >  	int old_status;
> >  	struct notifier_block notifier;
> > +	unsigned invert;
> >  };
> >
> >  static int fb_notifier_callback(struct notifier_block *p,
> > @@ -39,13 +40,15 @@ static int fb_notifier_callback(struct n
> >
> >  	switch (event) {
> >  	case FB_EVENT_BLANK :
> > -		if (*blank && n->old_status == UNBLANK) {
> > +		if ((!n->invert && *blank && n->old_status == UNBLANK) ||
> > +			    (n->invert && !*blank && n->old_status == BLANK)) {
> >  			n->brightness = led->brightness;
> >  			led_set_brightness(led, LED_OFF);
> > -			n->old_status = BLANK;
> > -		} else if (!*blank && n->old_status == BLANK) {
> > +			n->old_status = n->invert ? UNBLANK : BLANK;
> > +		} else if ((!n->invert && !*blank && n->old_status == BLANK) ||
> > +			    (n->invert && *blank && n->old_status == UNBLANK)) {
> >  			led_set_brightness(led, n->brightness);
> > -			n->old_status = UNBLANK;
> > +			n->old_status = n->invert ? BLANK : UNBLANK;
> >  		}
> >  		break;
> >  	}
>
> How about some like:
>
> unsigned new_status = *blank ? BLANK : UNBLANK;
>
> if (new_status != n->old_status) {
> 	if ((new_status ^ n->invert) == BLANK) {
> 		n->brightness = led->brightness;
> 		led_set_brightness(led, LED_OFF);
> 	} else {
> 		led_set_brightness(led, n->brightness);
> 	}
>
> 	n->old_status = new_status;
> }
>
> In my opinion that would be more readable.

Yes, you're right.

> > @@ -53,6 +56,43 @@ static int fb_notifier_callback(struct n
> >  	return 0;
> >  }
> >
> > +static ssize_t bl_trig_invert_show(struct device *dev,
> > +		struct device_attribute *attr, char *buf)
> > +{
> > +	struct led_classdev *led = dev_get_drvdata(dev);
> > +	struct bl_trig_notifier *n = led->trigger_data;
> > +
> > +	return sprintf(buf, "%s\n", n->invert ? "yes" : "no");
> > +}
> > +
> > +static ssize_t bl_trig_invert_store(struct device *dev,
> > +		struct device_attribute *attr, const char *buf, size_t num)
> > +{
> > +	struct led_classdev *led = dev_get_drvdata(dev);
> > +	struct bl_trig_notifier *n = led->trigger_data;
> > +	unsigned invert;
> > +	int ret;
> > +
> > +	ret = sscanf(buf, "%u", &invert);
> > +	if (ret < 1) {
> > +		dev_err(dev, "invalid value\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	n->invert = !!invert;
> > +
> > +	/* After inverting, we need to update the LED. */
> > +	if ((!n->invert && n->old_status == UNBLANK) ||
> > +			(n->invert && n->old_status == BLANK))
> > +		led_set_brightness(led, n->brightness);
> > +	else if ((!n->invert && n->old_status == BLANK) ||
> > +			(n->invert && n->old_status == UNBLANK))
> > +		led_set_brightness(led, LED_OFF);
> > +
> > +	return num;
> > +}
>
> Same here:
>
> if ((n->old_status ^ n->invert) == BLANK)
> 	led_set_brightness(led, LED_OFF);
> else
> 	led_set_brightness(led, n->brightness);

You're right again, thank you.

Please expect v2 soon.

Thanks,
Janusz

> > +static DEVICE_ATTR(invert, 0644, bl_trig_invert_show,
> > bl_trig_invert_store); +
> >  static void bl_trig_activate(struct led_classdev *led)
> >  {
> >  	int ret;
> > @@ -66,6 +106,10 @@ static void bl_trig_activate(struct led_
> >  		return;
> >  	}
> >
> > +	ret = device_create_file(led->dev, &dev_attr_invert);
> > +	if (ret)
> > +		goto err_invert;
> > +
> >  	n->led = led;
> >  	n->brightness = led->brightness;
> >  	n->old_status = UNBLANK;
> > @@ -74,6 +118,12 @@ static void bl_trig_activate(struct led_
> >  	ret = fb_register_client(&n->notifier);
> >  	if (ret)
> >  		dev_err(led->dev, "unable to register backlight trigger\n");
> > +
> > +	return;
> > +
> > +err_invert:
> > +	led->trigger_data = NULL;
> > +	kfree(n);
> >  }
> >
> >  static void bl_trig_deactivate(struct led_classdev *led)
> > @@ -82,6 +132,7 @@ static void bl_trig_deactivate(struct le
> >  		(struct bl_trig_notifier *) led->trigger_data;
> >
> >  	if (n) {
> > +		device_remove_file(led->dev, &dev_attr_invert);
> >  		fb_unregister_client(&n->notifier);
> >  		kfree(n);
> >  	}
> > --
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