mirror of https://gitee.com/openkylin/linux.git
leds: Add support for hardware accelerated LED flashing
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> Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
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@ -48,6 +48,26 @@ above leaves scope for further attributes should they be needed. If sections
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of the name don't apply, just leave that section blank.
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Hardware accelerated blink of LEDs
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==================================
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Some LEDs can be programmed to blink without any CPU interaction. To
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support this feature, a LED driver can optionally implement the
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blink_set() function (see <linux/leds.h>). If implemeted, triggers can
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attempt to use it before falling back to software timers. The blink_set()
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function should return 0 if the blink setting is supported, or -EINVAL
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otherwise, which means that LED blinking will be handled by software.
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The blink_set() function should choose a user friendly blinking
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value if it is called with *delay_on==0 && *delay_off==0 parameters. In
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this case the driver should give back the chosen value through delay_on
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and delay_off parameters to the leds subsystem.
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Any call to the brightness_set() callback function should cancel the
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previously programmed hardware blinking function so setting the brightness
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to 0 can also cancel the blinking of the LED.
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Known Issues
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============
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@ -56,10 +76,6 @@ would cause nightmare dependency issues. I see this as a minor issue
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compared to the benefits the simple trigger functionality brings. The
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rest of the LED subsystem can be modular.
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Some leds can be programmed to flash in hardware. As this isn't a generic
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LED device property, this should be exported as a device specific sysfs
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attribute rather than part of the class if this functionality is required.
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Future Development
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==================
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@ -152,7 +152,11 @@ config LEDS_TRIGGER_TIMER
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depends on LEDS_TRIGGERS
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help
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This allows LEDs to be controlled by a programmable timer
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via sysfs. If unsure, say Y.
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via sysfs. Some LED hardware can be programmed to start
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blinking the LED without any further software interaction.
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For more details read Documentation/leds-class.txt.
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If unsure, say Y.
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config LEDS_TRIGGER_IDE_DISK
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bool "LED IDE Disk Trigger"
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@ -77,8 +77,21 @@ static ssize_t led_delay_on_store(struct device *dev,
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count++;
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if (count == size) {
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if (timer_data->delay_on != state) {
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/* the new value differs from the previous */
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timer_data->delay_on = state;
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/* deactivate previous settings */
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del_timer_sync(&timer_data->timer);
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/* try to activate hardware acceleration, if any */
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if (!led_cdev->blink_set ||
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led_cdev->blink_set(led_cdev,
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&timer_data->delay_on, &timer_data->delay_off)) {
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/* no hardware acceleration, blink via timer */
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mod_timer(&timer_data->timer, jiffies + 1);
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}
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}
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ret = count;
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}
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@ -110,8 +123,21 @@ static ssize_t led_delay_off_store(struct device *dev,
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count++;
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if (count == size) {
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if (timer_data->delay_off != state) {
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/* the new value differs from the previous */
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timer_data->delay_off = state;
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/* deactivate previous settings */
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del_timer_sync(&timer_data->timer);
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/* try to activate hardware acceleration, if any */
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if (!led_cdev->blink_set ||
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led_cdev->blink_set(led_cdev,
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&timer_data->delay_on, &timer_data->delay_off)) {
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/* no hardware acceleration, blink via timer */
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mod_timer(&timer_data->timer, jiffies + 1);
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}
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}
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ret = count;
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}
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@ -143,6 +169,13 @@ static void timer_trig_activate(struct led_classdev *led_cdev)
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if (rc)
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goto err_out_delayon;
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/* If there is hardware support for blinking, start one
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* user friendly blink rate chosen by the driver.
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*/
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if (led_cdev->blink_set)
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led_cdev->blink_set(led_cdev,
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&timer_data->delay_on, &timer_data->delay_off);
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return;
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err_out_delayon:
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@ -38,6 +38,11 @@ struct led_classdev {
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void (*brightness_set)(struct led_classdev *led_cdev,
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enum led_brightness brightness);
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/* Activate hardware accelerated blink */
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int (*blink_set)(struct led_classdev *led_cdev,
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unsigned long *delay_on,
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unsigned long *delay_off);
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struct device *dev;
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struct list_head node; /* LED Device list */
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char *default_trigger; /* Trigger to use */
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