Re: [RESEND #2] [PATCH v2] LEDS: Add output invertion option to backlight trigger

[Paul Mundt <lethal@linux-sh.org>]

(Trying an alternate address for Richard, and adding Andrew to Cc..)

On Thu, Dec 09, 2010 at 02:41:50PM +0100, Janusz Krzysztofik wrote:
> This patch extends the LED backlight tirgger driver with an option that allows 
> for inverting the trigger output polarity.
> 
> With 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 the display was blanked, or the machine was turned off, 
> without touching it.
> 
> The invert sysfs control is patterned after a similiar function of the GPIO 
> trigger driver.
> 
> Created and tested against linux-2.6.36-rc5 on Amstrad Delta.
> Retested on linux-2.6.37-rc4.
> 
> Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> ---
> 
> Resent because I still can't see any response received, while yet another 
> merge window is going to pass away soon.
> 
> Applies cleanly on top of 2.6.37-rc4, so no need for yet another refresh. Only 
> tried to clean up the commit message slightly - maybe my English is not good 
> enough to bother with, if not the code?
> 
> v1 -> v2 changes:
> - improve some conditional expressions to be more readable; thanks to Ralph 
>   Corderoy (from e3-hacking) and Lars-Peter Clausen for their suggestions,
> - refresh against linux-2.6.36-rc5.
> 
>  drivers/leds/ledtrig-backlight.c |   60 
> ++++++++++++++++++++++++++++++++++++---
>  1 file changed, 56 insertions(+), 4 deletions(-)
> 
> diff -upr linux-2.6.36-rc5.orig/drivers/leds/ledtrig-backlight.c linux-2.6.36-rc5/drivers/leds/ledtrig-backlight.c
> --- linux-2.6.36-rc5.orig/drivers/leds/ledtrig-backlight.c	2010-09-24 15:35:13.000000000 +0200
> +++ linux-2.6.36-rc5/drivers/leds/ledtrig-backlight.c	2010-10-03 15:59:49.000000000 +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,
> @@ -36,23 +37,63 @@ static int fb_notifier_callback(struct n
>  	struct led_classdev *led = n->led;
>  	struct fb_event *fb_event = data;
>  	int *blank = fb_event->data;
> +	int new_status = *blank ? BLANK : UNBLANK;
>  
>  	switch (event) {
>  	case FB_EVENT_BLANK :
> -		if (*blank && n->old_status = UNBLANK) {
> +		if (new_status = n->old_status)
> +			break;
> +
> +		if ((n->old_status = UNBLANK) ^ n->invert) {
>  			n->brightness = led->brightness;
>  			led_set_brightness(led, LED_OFF);
> -			n->old_status = BLANK;
> -		} else if (!*blank && n->old_status = BLANK) {
> +		} else {
>  			led_set_brightness(led, n->brightness);
> -			n->old_status = UNBLANK;
>  		}
> +
> +		n->old_status = new_status;
> +
>  		break;
>  	}
>  
>  	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->old_status = BLANK) ^ n->invert)
> +		led_set_brightness(led, LED_OFF);
> +	else
> +		led_set_brightness(led, n->brightness);
> +
> +	return num;
> +}
> +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 +107,10 @@ 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 +119,12 @@ 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 +133,7 @@ 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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