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    Subject[PATCH 3/4] leds-clevo-mail: hw accelerated LED blink extension
    From: Márton Németh <nm127@freemail.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@freemail.hu>
    ---
    diff -uprN linux-2.6.24-rc1.b/Documentation/leds-class.txt linux-2.6.24-rc1.c/Documentation/leds-class.txt
    --- linux-2.6.24-rc1.b/Documentation/leds-class.txt 2007-10-28 09:20:07.000000000 +0100
    +++ linux-2.6.24-rc1.c/Documentation/leds-class.txt 2007-10-28 09:35:54.000000000 +0100
    @@ -49,6 +49,27 @@ 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.
    +
    +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
    ============

    @@ -57,10 +78,6 @@ 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-2.6.24-rc1.b/drivers/leds/Kconfig linux-2.6.24-rc1.c/drivers/leds/Kconfig
    --- linux-2.6.24-rc1.b/drivers/leds/Kconfig 2007-10-28 09:13:13.000000000 +0100
    +++ linux-2.6.24-rc1.c/drivers/leds/Kconfig 2007-10-28 09:09:45.000000000 +0100
    @@ -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 -uprN linux-2.6.24-rc1.b/drivers/leds/ledtrig-timer.c linux-2.6.24-rc1.c/drivers/leds/ledtrig-timer.c
    --- linux-2.6.24-rc1.b/drivers/leds/ledtrig-timer.c 2007-10-28 09:01:56.000000000 +0100
    +++ linux-2.6.24-rc1.c/drivers/leds/ledtrig-timer.c 2007-10-28 08:16:50.000000000 +0100
    @@ -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;
    }

    @@ -143,6 +169,13 @@ static void timer_trig_activate(struct l
    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 -uprN linux-2.6.24-rc1.b/include/linux/leds.h linux-2.6.24-rc1.c/include/linux/leds.h
    --- linux-2.6.24-rc1.b/include/linux/leds.h 2007-10-28 09:01:56.000000000 +0100
    +++ linux-2.6.24-rc1.c/include/linux/leds.h 2007-10-28 10:04:14.000000000 +0100
    @@ -37,6 +37,11 @@ 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 */
    -
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