From 9f9455ae710786bd11625d501567f4f783fedea5 Mon Sep 17 00:00:00 2001 From: Janusz Krzysztofik Date: Wed, 12 Jan 2011 16:59:20 -0800 Subject: [PATCH] leds: add output inversion option to backlight trigger Extend 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. [akpm@linux-foundation.org: make output match input, tighten input checking] [akpm@linux-foundation.org: make output match input, tighten input checking] Signed-off-by: Janusz Krzysztofik Cc: Paul Mundt Acked-by: Richard Purdie Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/ABI/testing/sysfs-class-led | 9 +++++ drivers/leds/ledtrig-backlight.c | 61 +++++++++++++++++++++++++++++-- 2 files changed, 66 insertions(+), 4 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led index 9e4541d..edff663 100644 --- a/Documentation/ABI/testing/sysfs-class-led +++ b/Documentation/ABI/testing/sysfs-class-led @@ -26,3 +26,12 @@ Description: scheduler is chosen. Trigger specific parameters can appear in /sys/class/leds/ once a given trigger is selected. +What: /sys/class/leds//inverted +Date: January 2011 +KernelVersion: 2.6.38 +Contact: Richard Purdie +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. diff --git a/drivers/leds/ledtrig-backlight.c b/drivers/leds/ledtrig-backlight.c index f948e57..2b513a2 100644 --- a/drivers/leds/ledtrig-backlight.c +++ b/drivers/leds/ledtrig-backlight.c @@ -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 notifier_block *p, 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_classdev *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_classdev *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 led_classdev *led) (struct bl_trig_notifier *) led->trigger_data; if (n) { + device_remove_file(led->dev, &dev_attr_inverted); fb_unregister_client(&n->notifier); kfree(n); } -- 2.7.4