9f9455ae71
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 <jkrzyszt@tis.icnet.pl> Cc: Paul Mundt <lethal@linux-sh.org> Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
165 lines
3.6 KiB
C
165 lines
3.6 KiB
C
/*
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* Backlight emulation LED trigger
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*
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* Copyright 2008 (C) Rodolfo Giometti <giometti@linux.it>
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* Copyright 2008 (C) Eurotech S.p.A. <info@eurotech.it>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/fb.h>
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#include <linux/leds.h>
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#include "leds.h"
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#define BLANK 1
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#define UNBLANK 0
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struct bl_trig_notifier {
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struct led_classdev *led;
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int brightness;
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int old_status;
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struct notifier_block notifier;
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unsigned invert;
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};
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static int fb_notifier_callback(struct notifier_block *p,
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unsigned long event, void *data)
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{
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struct bl_trig_notifier *n = container_of(p,
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struct bl_trig_notifier, notifier);
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struct led_classdev *led = n->led;
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struct fb_event *fb_event = data;
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int *blank = fb_event->data;
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int new_status = *blank ? BLANK : UNBLANK;
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switch (event) {
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case FB_EVENT_BLANK :
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if (new_status == n->old_status)
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break;
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if ((n->old_status == UNBLANK) ^ n->invert) {
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n->brightness = led->brightness;
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led_set_brightness(led, LED_OFF);
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} else {
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led_set_brightness(led, n->brightness);
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}
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n->old_status = new_status;
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break;
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}
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return 0;
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}
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static ssize_t bl_trig_invert_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct led_classdev *led = dev_get_drvdata(dev);
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struct bl_trig_notifier *n = led->trigger_data;
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return sprintf(buf, "%u\n", n->invert);
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}
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static ssize_t bl_trig_invert_store(struct device *dev,
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struct device_attribute *attr, const char *buf, size_t num)
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{
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struct led_classdev *led = dev_get_drvdata(dev);
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struct bl_trig_notifier *n = led->trigger_data;
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unsigned long invert;
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int ret;
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ret = strict_strtoul(buf, 10, &invert);
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if (ret < 0)
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return ret;
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if (invert > 1)
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return -EINVAL;
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n->invert = invert;
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/* After inverting, we need to update the LED. */
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if ((n->old_status == BLANK) ^ n->invert)
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led_set_brightness(led, LED_OFF);
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else
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led_set_brightness(led, n->brightness);
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return num;
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}
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static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
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static void bl_trig_activate(struct led_classdev *led)
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{
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int ret;
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struct bl_trig_notifier *n;
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n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
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led->trigger_data = n;
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if (!n) {
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dev_err(led->dev, "unable to allocate backlight trigger\n");
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return;
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}
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ret = device_create_file(led->dev, &dev_attr_inverted);
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if (ret)
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goto err_invert;
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n->led = led;
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n->brightness = led->brightness;
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n->old_status = UNBLANK;
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n->notifier.notifier_call = fb_notifier_callback;
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ret = fb_register_client(&n->notifier);
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if (ret)
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dev_err(led->dev, "unable to register backlight trigger\n");
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return;
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err_invert:
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led->trigger_data = NULL;
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kfree(n);
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}
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static void bl_trig_deactivate(struct led_classdev *led)
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{
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struct bl_trig_notifier *n =
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(struct bl_trig_notifier *) led->trigger_data;
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if (n) {
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device_remove_file(led->dev, &dev_attr_inverted);
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fb_unregister_client(&n->notifier);
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kfree(n);
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}
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}
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static struct led_trigger bl_led_trigger = {
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.name = "backlight",
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.activate = bl_trig_activate,
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.deactivate = bl_trig_deactivate
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};
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static int __init bl_trig_init(void)
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{
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return led_trigger_register(&bl_led_trigger);
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}
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static void __exit bl_trig_exit(void)
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{
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led_trigger_unregister(&bl_led_trigger);
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}
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module_init(bl_trig_init);
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module_exit(bl_trig_exit);
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MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
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MODULE_DESCRIPTION("Backlight emulation LED trigger");
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MODULE_LICENSE("GPL v2");
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