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Subject[PATCH 2/3] leds-clevo-mail: hw accelerated LED blink extension
From: Márton Németh <nm127@freemail.hu>

Extends the leds subsystem with a blink_set() callback function which can
optionally implemented by a LED driver. If implemented, the driver can use the
hardware acceleration for blinking a LED.

Signed-off-by: Márton Németh <nm127@freemail.hu>
---
diff -uprN linux-2.6.22.orig/Documentation/leds-class.txt linux-2.6.22/Documentation/leds-class.txt
--- linux-2.6.22.orig/Documentation/leds-class.txt 2007-07-09 01:32:17.000000000 +0200
+++ linux-2.6.22/Documentation/leds-class.txt 2007-07-16 20:53:38.000000000 +0200
@@ -47,6 +47,17 @@ overhead, I suggest these become part of
above leaves scope for further attributes should they be needed.


+Hardware accelerated blink of LEDs
+==================================
+
+Some LEDs can be programmed to blink without any CPU interaction. To
+support this feature, a LED driver can optionally implement the
+blink_set() function (see <linux/leds.h>). If implemeted, the
+ledtrig-timer tries to use it. The blink_set() function should return
+1 if the blink setting is supported, or 0 otherwise, which means that
+the LED will be turned on and off from software.
+
+
Known Issues
============

@@ -55,10 +66,6 @@ would cause nightmare dependency issues.
compared to the benefits the simple trigger functionality brings. The
rest of the LED subsystem can be modular.

-Some leds can be programmed to flash in hardware. As this isn't a generic
-LED device property, this should be exported as a device specific sysfs
-attribute rather than part of the class if this functionality is required.
-

Future Development
==================
diff -uprN linux-2.6.22.orig/drivers/leds/ledtrig-timer.c linux-2.6.22/drivers/leds/ledtrig-timer.c
--- linux-2.6.22.orig/drivers/leds/ledtrig-timer.c 2007-07-09 01:32:17.000000000 +0200
+++ linux-2.6.22/drivers/leds/ledtrig-timer.c 2007-07-17 09:43:20.000000000 +0200
@@ -76,8 +76,21 @@ static ssize_t led_delay_on_store(struct
count++;

if (count == size) {
- timer_data->delay_on = state;
- mod_timer(&timer_data->timer, jiffies + 1);
+ if (timer_data->delay_on != state) {
+ /* the new value differs from the previous */
+ timer_data->delay_on = state;
+
+ /* deactivate previous settings */
+ del_timer_sync(&timer_data->timer);
+
+ /* try to activate hardware acceleration, if any */
+ if (!led_cdev->blink_set ||
+ !led_cdev->blink_set(led_cdev,
+ timer_data->delay_on, timer_data->delay_off)) {
+ /* no hardware acceleration, blink via timer */
+ mod_timer(&timer_data->timer, jiffies + 1);
+ }
+ }
ret = count;
}

@@ -108,8 +121,21 @@ static ssize_t led_delay_off_store(struc
count++;

if (count == size) {
- timer_data->delay_off = state;
- mod_timer(&timer_data->timer, jiffies + 1);
+ if (timer_data->delay_off != state) {
+ /* the new value differs from the previous */
+ timer_data->delay_off = state;
+
+ /* deactivate previous settings */
+ del_timer_sync(&timer_data->timer);
+
+ /* try to activate hardware acceleration, if any */
+ if (!led_cdev->blink_set ||
+ !led_cdev->blink_set(led_cdev,
+ timer_data->delay_on, timer_data->delay_off)) {
+ /* no hardware acceleration, blink via timer */
+ mod_timer(&timer_data->timer, jiffies + 1);
+ }
+ }
ret = count;
}

diff -uprN linux-2.6.22.orig/include/linux/leds.h linux-2.6.22/include/linux/leds.h
--- linux-2.6.22.orig/include/linux/leds.h 2007-07-09 01:32:17.000000000 +0200
+++ linux-2.6.22/include/linux/leds.h 2007-07-16 20:53:38.000000000 +0200
@@ -38,6 +38,11 @@ struct led_classdev {
void (*brightness_set)(struct led_classdev *led_cdev,
enum led_brightness brightness);

+ /* Activate hardware accelerated blink */
+ int (*blink_set)(struct led_classdev *led_cdev,
+ int delay_on, int delay_off);
+
+
struct class_device *class_dev;
struct list_head node; /* LED Device list */
char *default_trigger; /* Trigger to use */
-
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