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Subject[PATCH 3/4] 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
be 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-2.6.24-rc1.b/Documentation/leds-class.txt linux-2.6.24-rc1.c/Documentation/leds-class.txt
--- linux-2.6.24-rc1.b/Documentation/leds-class.txt 2007-10-28 09:20:07.000000000 +0100
+++ linux-2.6.24-rc1.c/Documentation/leds-class.txt 2007-10-28 09:35:54.000000000 +0100
@@ -49,6 +49,27 @@ 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
+0 if the blink setting is supported, or -EINVAL otherwise, which means
+that the LED will be turned on and off from software by the leds
+subsystem.
+
+The blink_set() function should choose a user friendly blinking
+value if it is called with *delay_on==0 && *delay_off==0 parameters. In
+this case the driver should give back the chosen value through delay_on
+and delay_off parameters to the leds subsystem.
+
+Any call to the brightness_set() callback function should cancel the
+previously programmed hardware blinking function so setting the brightness
+to 0 can also cancel the blinking of the LED.
+
+
Known Issues
============

@@ -57,10 +78,6 @@ 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-2.6.24-rc1.b/drivers/leds/Kconfig linux-2.6.24-rc1.c/drivers/leds/Kconfig
--- linux-2.6.24-rc1.b/drivers/leds/Kconfig 2007-10-28 09:13:13.000000000 +0100
+++ linux-2.6.24-rc1.c/drivers/leds/Kconfig 2007-10-28 09:09:45.000000000 +0100
@@ -152,7 +152,11 @@ config LEDS_TRIGGER_TIMER
depends on LEDS_TRIGGERS
help
This allows LEDs to be controlled by a programmable timer
- via sysfs. If unsure, say Y.
+ via sysfs. Some LED hardware can be programmed to start
+ blinking the LED without any further software interaction.
+ For more details read Documentation/leds-class.txt.
+
+ If unsure, say Y.

config LEDS_TRIGGER_IDE_DISK
bool "LED IDE Disk Trigger"
diff -uprN linux-2.6.24-rc1.b/drivers/leds/ledtrig-timer.c linux-2.6.24-rc1.c/drivers/leds/ledtrig-timer.c
--- linux-2.6.24-rc1.b/drivers/leds/ledtrig-timer.c 2007-10-28 09:01:56.000000000 +0100
+++ linux-2.6.24-rc1.c/drivers/leds/ledtrig-timer.c 2007-10-28 08:16:50.000000000 +0100
@@ -77,8 +77,21 @@ 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;
}

@@ -110,8 +123,21 @@ 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;
}

@@ -143,6 +169,13 @@ static void timer_trig_activate(struct l
if (rc)
goto err_out_delayon;

+ /* If there is hardware support for blinking, start one
+ * user friendly blink rate chosen by the driver.
+ */
+ if (led_cdev->blink_set)
+ led_cdev->blink_set(led_cdev,
+ &timer_data->delay_on, &timer_data->delay_off);
+
return;

err_out_delayon:
diff -uprN linux-2.6.24-rc1.b/include/linux/leds.h linux-2.6.24-rc1.c/include/linux/leds.h
--- linux-2.6.24-rc1.b/include/linux/leds.h 2007-10-28 09:01:56.000000000 +0100
+++ linux-2.6.24-rc1.c/include/linux/leds.h 2007-10-28 10:04:14.000000000 +0100
@@ -37,6 +37,11 @@ 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,
+ unsigned long *delay_on,
+ unsigned long *delay_off);
+
struct device *dev;
struct list_head node; /* LED Device list */
char *default_trigger; /* Trigger to use */
-
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