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

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

[Janusz Krzysztofik]

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);
 	}

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

[Paul Mundt]

(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);
>  	}
> --
> To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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

[Richard Purdie]

On Thu, 2011-01-06 at 16:08 +0900, Paul Mundt wrote:
> (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>

Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>

I'll let Andrew take the patch though.

> > ---
> > 
> > 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);
> >  	}
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

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

[Andrew Morton]

On Thu, 9 Dec 2010 14:41:50 +0100
Janusz Krzysztofik <jkrzyszt@tis.icnet.pl> 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");
> +}

I think this should show "0" or "1", to match the thing which the user
wrote here.

> +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);

Here we should use strict_strtoul() so the kernel correctly rejects
input of the form "42foo".

> +	if (ret < 1) {
> +		dev_err(dev, "invalid value\n");
> +		return -EINVAL;
> +	}

And here it would be better to disallow any input other than 0 or 1. 
Because "2" makes no sense and who knows, some time in the future we
might *want* to permit 2.

So...

--- a/drivers/leds/ledtrig-backlight.c~leds-add-output-inversion-option-to-backlight-trigger-fix
+++ a/drivers/leds/ledtrig-backlight.c
@@ -65,7 +65,7 @@ static ssize_t bl_trig_invert_show(struc
 	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");
+	return sprintf(buf, "%u\n", n->invert);
 }
 
 static ssize_t bl_trig_invert_store(struct device *dev,
@@ -73,16 +73,17 @@ static ssize_t bl_trig_invert_store(stru
 {
 	struct led_classdev *led = dev_get_drvdata(dev);
 	struct bl_trig_notifier *n = led->trigger_data;
-	unsigned invert;
+	unsigned long invert;
 	int ret;
 
-	ret = sscanf(buf, "%u", &invert);
-	if (ret < 1) {
-		dev_err(dev, "invalid value\n");
+	ret = strict_strtoul(buf, 10, &invert);
+	if (ret < 0)
+		return ret;
+
+	if (invert > 1)
 		return -EINVAL;
-	}
 
-	n->invert = !!invert;
+	n->invert = invert;
 
 	/* After inverting, we need to update the LED. */
 	if ((n->old_status = BLANK) ^ n->invert)
_


Could you help test it please?

> +static DEVICE_ATTR(invert, 0644, bl_trig_invert_show, bl_trig_invert_store);

This new sysfs file should be documented.  Where would be an
appropriate place for that?  Documentation/leds-class.txt doesn't
mention a sysfs API at all.  

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

[Randy Dunlap]

On Thu, 6 Jan 2011 13:04:40 -0800 Andrew Morton wrote:

> On Thu, 9 Dec 2010 14:41:50 +0100
> Janusz Krzysztofik <jkrzyszt@tis.icnet.pl> wrote:
> 
> > +static DEVICE_ATTR(invert, 0644, bl_trig_invert_show, bl_trig_invert_store);
> 
> This new sysfs file should be documented.  Where would be an
> appropriate place for that?  Documentation/leds-class.txt doesn't
> mention a sysfs API at all.  
> --

in Documentation/ABI/, where all sysfs interface info lives.

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

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

[Andrew Morton]

On Thu, 6 Jan 2011 13:08:56 -0800
Randy Dunlap <randy.dunlap@oracle.com> wrote:

> On Thu, 6 Jan 2011 13:04:40 -0800 Andrew Morton wrote:
> 
> > On Thu, 9 Dec 2010 14:41:50 +0100
> > Janusz Krzysztofik <jkrzyszt@tis.icnet.pl> wrote:
> > 
> > > +static DEVICE_ATTR(invert, 0644, bl_trig_invert_show, bl_trig_invert_store);
> > 
> > This new sysfs file should be documented.  Where would be an
> > appropriate place for that?  Documentation/leds-class.txt doesn't
> > mention a sysfs API at all.  
> > --
> 
> in Documentation/ABI/, where all sysfs interface info lives.
> 

Spose so.  Documentation/ABI/stable/sysfs-class-backlight does have
some stuff in it.

Personally I tend to regard Documentation/ABI/ as fairly useless
incomprehensible stuff, maintained to keep Greg happy ;) It'd be better
to have a nice little well-maintained document for a subsystem such as
this which actually explains its operation in a useful-to-humans way. 
Rather than just mechanically filling out forms.

But a Documentation/ABI update is a heck of a lot better than nothing.

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

[Randy Dunlap]

On 01/06/11 13:16, Andrew Morton wrote:
> On Thu, 6 Jan 2011 13:08:56 -0800
> Randy Dunlap <randy.dunlap@oracle.com> wrote:
> 
>> On Thu, 6 Jan 2011 13:04:40 -0800 Andrew Morton wrote:
>>
>>> On Thu, 9 Dec 2010 14:41:50 +0100
>>> Janusz Krzysztofik <jkrzyszt@tis.icnet.pl> wrote:
>>>
>>>> +static DEVICE_ATTR(invert, 0644, bl_trig_invert_show, bl_trig_invert_store);
>>>
>>> This new sysfs file should be documented.  Where would be an
>>> appropriate place for that?  Documentation/leds-class.txt doesn't
>>> mention a sysfs API at all.  
>>> --
>>
>> in Documentation/ABI/, where all sysfs interface info lives.
>>
> 
> Spose so.  Documentation/ABI/stable/sysfs-class-backlight does have
> some stuff in it.
> 
> Personally I tend to regard Documentation/ABI/ as fairly useless
> incomprehensible stuff, maintained to keep Greg happy ;) It'd be better
> to have a nice little well-maintained document for a subsystem such as
> this which actually explains its operation in a useful-to-humans way. 
> Rather than just mechanically filling out forms.
> 
> But a Documentation/ABI update is a heck of a lot better than nothing.

Yes, I was giving you the "where it currently lives", not "what is best."
I agree with you.

-- 
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***

[PATCH v3] LEDS: Add output invertion option to backlight trigger

[Janusz Krzysztofik]

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-2.6.37 on Amstrad Delta.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Cc: Richard Purdie <rpurdie@rpsys.net>
---

v2 -> v3 changes, all provided, requested or inspired by Andrew Morton 
  (thanks!):
- sysfs file should show "0" or "1" to match the thing which the user
  wrote there,
- use strict_strtoul() so the kernel correctly rejects non-numerical 
  input,
- disallow any input other than 0 or 1,
- new sysfs file should be documented,
- the new sysfs file name could be consistent with the one already used 
  by the gpio trigger for a similiar function.

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.

 Documentation/ABI/testing/sysfs-class-led |   10 ++++
 drivers/leds/ledtrig-backlight.c          |   61 ++++++++++++++++++++++++++++--
 2 files changed, 67 insertions(+), 4 deletions(-)

--- linux-2.6.37/drivers/leds/ledtrig-backlight.c.orig	2011-01-10 02:55:26.000000000 +0100
+++ linux-2.6.37/drivers/leds/ledtrig-backlight.c	2011-01-10 03:12:46.000000000 +0100
@@ -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 +37,64 @@ 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, "%u\n", n->invert);
+}
+
+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 long invert;
+	int ret;
+
+	ret = strict_strtoul(buf, 10, &invert);
+	if (ret < 0)
+		return ret;
+
+	if (invert > 1)
+		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(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
+
 static void bl_trig_activate(struct led_classdev *led)
 {
 	int ret;
@@ -66,6 +108,10 @@ static void bl_trig_activate(struct led_
 		return;
 	}
 
+	ret = device_create_file(led->dev, &dev_attr_inverted);
+	if (ret)
+		goto err_invert;
+
 	n->led = led;
 	n->brightness = led->brightness;
 	n->old_status = UNBLANK;
@@ -74,6 +120,12 @@ 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 +134,7 @@ static void bl_trig_deactivate(struct le
 		(struct bl_trig_notifier *) led->trigger_data;
 
 	if (n) {
+		device_remove_file(led->dev, &dev_attr_inverted);
 		fb_unregister_client(&n->notifier);
 		kfree(n);
 	}
--- linux-2.6.37/Documentation/ABI/testing/sysfs-class-led.orig	2011-01-10 02:42:16.000000000 +0100
+++ linux-2.6.37/Documentation/ABI/testing/sysfs-class-led	2011-01-10 03:38:28.000000000 +0100
@@ -26,3 +26,13 @@ Description:
 		scheduler is chosen. Trigger specific parameters can appear in
 		/sys/class/leds/<led> once a given trigger is selected.
 
+What:		/sys/class/leds/<led>/inverted
+Date:		January 2011
+KernelVersion:	2.6.38
+Contact:	Richard Purdie <rpurdie@rpsys.net>
+Description:
+		Invert the LED on/off state. This parameter is specific to
+		gpio and backlight triggers. In case of the backlight trigger,
+		it is usefull when driving a LED which is intended to indicate
+		a device in a standby like state.
+