linux-kernel - [PATCH 2/3] leds-clevo-mail: hw accelerated LED blink extension

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Message-ID: <4718FCF3.4030401@freemail.hu>
Date:	Fri, 19 Oct 2007 20:52:35 +0200
From:	Németh Márton <nm127@...email.hu>
To:	Richard Purdie <rpurdie@...ys.net>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	linux-kernel@...r.kernel.org, Rodrigo Pereira <rodripe@...il.com>
Subject: [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	2007-10-18 06:57:37.000000000 +0200
@@ -47,6 +47,18 @@ 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 +67,6 @@ 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/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 07:15:14.000000000 +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 07:17:30.000000000 +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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