From 4c79141d28bc290ae307e3f81f5bc909c26faf6e Mon Sep 17 00:00:00 2001 From: =?utf8?q?M=C3=A1rton=20N=C3=A9meth?= Date: Wed, 31 Oct 2007 15:07:12 +0100 Subject: [PATCH] leds: Add support for hardware accelerated LED flashing MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Richard Purdie --- Documentation/leds-class.txt | 24 +++++++++++++++++---- drivers/leds/Kconfig | 6 +++++- drivers/leds/ledtrig-timer.c | 41 ++++++++++++++++++++++++++++++++---- include/linux/leds.h | 5 +++++ 4 files changed, 67 insertions(+), 9 deletions(-) diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt index 877af6efc1..56757c751d 100644 --- a/Documentation/leds-class.txt +++ b/Documentation/leds-class.txt @@ -48,6 +48,26 @@ above leaves scope for further attributes should they be needed. If sections of the name don't apply, just leave that section blank. +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 ). If implemeted, triggers can +attempt to use it before falling back to software timers. The blink_set() +function should return 0 if the blink setting is supported, or -EINVAL +otherwise, which means that LED blinking will be handled by software. + +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 ============ @@ -56,10 +76,6 @@ would cause nightmare dependency issues. I see this as a minor issue 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 --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig index cf3a6d4d94..659448ead6 100644 --- a/drivers/leds/Kconfig +++ b/drivers/leds/Kconfig @@ -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 --git a/drivers/leds/ledtrig-timer.c b/drivers/leds/ledtrig-timer.c index ed9ff02c77..82c55d6e49 100644 --- a/drivers/leds/ledtrig-timer.c +++ b/drivers/leds/ledtrig-timer.c @@ -77,8 +77,21 @@ static ssize_t led_delay_on_store(struct device *dev, 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(struct device *dev, 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 led_classdev *led_cdev) 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 --git a/include/linux/leds.h b/include/linux/leds.h index 00f89fd6c5..0201f6f51c 100644 --- a/include/linux/leds.h +++ b/include/linux/leds.h @@ -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, + unsigned long *delay_on, + unsigned long *delay_off); + struct device *dev; struct list_head node; /* LED Device list */ char *default_trigger; /* Trigger to use */ -- 2.39.5