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Date: Sun, 21 Oct 2007 14:54:10 +0200
From: Németh Márton <nm127@...email.hu>
To: Randy Dunlap <randy.dunlap@...cle.com>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Richard Purdie <rpurdie@...ys.net>
CC: linux-kernel@...r.kernel.org, Rodrigo Pereira <rodripe@...il.com>
Subject: Re: [PATCH 2/3] leds-clevo-mail: hw accelerated LED blink extension
From: Márton Németh <nm127@...email.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@...email.hu>
---
diff -uprN linux-2.6.23.orig/Documentation/leds-class.txt linux-2.6.23/Documentation/leds-class.txt
--- linux-2.6.23.orig/Documentation/leds-class.txt 2007-10-09 22:31:38.000000000 +0200
+++ linux-2.6.23/Documentation/leds-class.txt 2007-10-21 10:45:35.000000000 +0200
@@ -47,6 +49,19 @@ 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.
+
+
Known Issues
============
@@ -55,10 +70,6 @@ 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-2.6.23.orig/drivers/leds/Kconfig linux-2.6.23/drivers/leds/Kconfig
--- linux-2.6.23.orig/drivers/leds/Kconfig 2007-10-09 22:31:38.000000000 +0200
+++ linux-2.6.23/drivers/leds/Kconfig 2007-10-21 12:04:50.000000000 +0200
@@ -115,7 +148,11 @@ 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-2.6.23.orig/drivers/leds/ledtrig-timer.c linux-2.6.23/drivers/leds/ledtrig-timer.c
--- linux-2.6.23.orig/drivers/leds/ledtrig-timer.c 2007-10-09 22:31:38.000000000 +0200
+++ linux-2.6.23/drivers/leds/ledtrig-timer.c 2007-10-18 18:21:34.000000000 +0200
@@ -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;
}
diff -uprN linux-2.6.23.orig/include/linux/leds.h linux-2.6.23/include/linux/leds.h
--- linux-2.6.23.orig/include/linux/leds.h 2007-10-09 22:31:38.000000000 +0200
+++ linux-2.6.23/include/linux/leds.h 2007-10-18 18:21:34.000000000 +0200
@@ -37,6 +37,10 @@ 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 device *dev;
struct list_head node; /* LED Device list */
char *default_trigger; /* Trigger to use */
-
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