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

Janusz Krzysztofik
2010-12-09T13:42:43Z

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);
}