leds-clevo-mail: hw accelerated LED blink extension

PATCH In review Németh Márton 2 participants 3 messages Oct 19, 2007 – Oct 23, 2007

Subsystems (2)

Documentation LED

lore

Share & tools

lore

Németh Márton

author

2007-10-19 18:55 UTC #0 lore raw

PATCH 2/3 leds-clevo-mail: hw accelerated LED blink extension

From: Márton Németh <[email protected]>

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 <[email protected]>

---

Documentation/leds-class.txt +12 -4

diff -uprN linux-2.6.23.orig/Documentation/leds-class.txt linux-2.6.23/Documentation/leds-class.txt
@@ -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
 ==================

drivers/leds/ledtrig-timer.c +30 -4

diff -uprN linux-2.6.23.orig/drivers/leds/ledtrig-timer.c linux-2.6.23/drivers/leds/ledtrig-timer.c
@@ -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;
 	}

include/linux/leds.h +4 -0

diff -uprN linux-2.6.23.orig/include/linux/leds.h linux-2.6.23/include/linux/leds.h
@@ -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 */

Németh Márton

author

2007-10-21 12:57 UTC #1 lore raw

From: Márton Németh <[email protected]>

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 <[email protected]>

---

Documentation/leds-class.txt +13 -4

diff -uprN linux-2.6.23.orig/Documentation/leds-class.txt linux-2.6.23/Documentation/leds-class.txt
@@ -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
 ==================

drivers/leds/Kconfig +5 -1

diff -uprN linux-2.6.23.orig/drivers/leds/Kconfig linux-2.6.23/drivers/leds/Kconfig
@@ -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"

drivers/leds/ledtrig-timer.c +30 -4

diff -uprN linux-2.6.23.orig/drivers/leds/ledtrig-timer.c linux-2.6.23/drivers/leds/ledtrig-timer.c
@@ -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;
 	}

include/linux/leds.h +4 -0

diff -uprN linux-2.6.23.orig/include/linux/leds.h linux-2.6.23/include/linux/leds.h
@@ -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 */

Richard Purdie

2007-10-23 21:50 UTC #2 lore raw

Quoted 16 lines · Németh Márton

From: Márton Németh <[email protected]>
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 <[email protected]>
---
diff -uprN linux-2.6.23.orig/Documentation/leds-class.txt linux-2.6.23/Documentation/leds-class.txt
Documentation/leds-class.txt +1 -0
@@ -47,6 +49,19 @@ overhead, I suggest these become part of
 above leaves scope for further attributes should they be needed.
 
 
+

Documentation/leds-class.txt overhead, I suggest these become part of · line 62

Quoted 10 lines

Documentation/leds-class.txt +10 -0

+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.

Hardware acceleration of the timer triggers is great to see and worst case I'll happily apply this patch to the LED tree, thanks.

Before I do, I did wonder if we should enhance the meaning of the set_blink function a bit. If set_blink is called with delay_on = 0, delay_off = 0 it could mean "blink with some user friendly value, hardware assisted". The use for this would be a more generic blink trigger where you wouldn't need to know about magically hardware assisted values for blinking, it would simply make an LED blink in a hardware assisted way.

We also need to document that the brightness_set overrides any blinking which may or may not be active (which is implied in your driver).

Cheers,

Richard