[PATCH 4/4] leds: Let GPIO LEDs keep their current state

[Grant Likely]

On Fri, Oct 24, 2008 at 5:09 PM, Trent Piepho <tpiepho at freescale.com> wrote:
> Let GPIO LEDs get their initial value from whatever the current state of
> the GPIO line is.  On some systems the LEDs are put into some state by the
> firmware or hardware before Linux boots, and it is desired to have them
> keep this state which is otherwise unknown to Linux.
>
> This requires that the underlying GPIO driver support reading the value of
> output GPIOs.  Some drivers support this and some do not.
>
> The platform data for the platform device binding gets a new field
> 'keep_state' which turns this on.  keep_state overrides default_state.
>
> For the OpenFirmware bindings, the "default-state" property gains a new
> allowable setting "keep".

Hmmm... I'd prefer firmware to actually update the device tree if the
LED state needs to be preserved.  In fact, it might be better use the
name "current-state" instead of "default-state" similar to the
current-speed property used in serial devices.  However, I understand
that there are practical implications with this were not all firmware
is device tree aware.  I don't see any reason not to support this
approach, so:

Acked-by: Grant Likely <grant.likely at secretlab.ca>

(But consider changing the property name)

This is a good patch series, thanks.
g.

>
> Signed-off-by: Trent Piepho <tpiepho at freescale.com>
> ---
>  Documentation/powerpc/dts-bindings/gpio/led.txt |   16 ++++++++++++----
>  drivers/leds/leds-gpio.c                        |   12 ++++++++----
>  include/linux/leds.h                            |    3 ++-
>  3 files changed, 22 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/powerpc/dts-bindings/gpio/led.txt b/Documentation/powerpc/dts-bindings/gpio/led.txt
> index 544ded7..918bf9f 100644
> --- a/Documentation/powerpc/dts-bindings/gpio/led.txt
> +++ b/Documentation/powerpc/dts-bindings/gpio/led.txt
> @@ -21,10 +21,12 @@ LED sub-node properties:
>     "ide-disk" - LED indicates disk activity
>     "timer" - LED flashes at a fixed, configurable rate
>  - default-state:  (optional) The initial state of the LED.  Valid
> -  values are "on" and "off".  If the LED is already on or off and the
> -  default-state property is set the to same value, then no glitch
> -  should be produced where the LED momentarily turns off (or on).
> -  The default is off if this property is not present.
> +  values are "on", "off", and "keep".  If the LED is already on or off
> +  and the default-state property is set the to same value, then no
> +  glitch should be produced where the LED momentarily turns off (or
> +  on).  The "keep" setting will keep the LED at whatever its current
> +  state is, without producing a glitch.  The default is off if this
> +  property is not present.
>
>  Examples:
>
> @@ -35,6 +37,12 @@ leds {
>                gpios = <&mcu_pio 0 1>; /* Active low */
>                linux,default-trigger = "ide-disk";
>        };
> +
> +       fault {
> +               gpios = <&mcu_pio 1 0>;
> +               /* Keep LED on if BIOS detected hardware fault */
> +               default-state = "keep";
> +       };
>  };
>
>  run-control {
> diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
> index 0dbad87..bb2a234 100644
> --- a/drivers/leds/leds-gpio.c
> +++ b/drivers/leds/leds-gpio.c
> @@ -76,7 +76,7 @@ static int __devinit create_gpio_led(const struct gpio_led *template,
>        struct gpio_led_data *led_dat, struct device *parent,
>        int (*blink_set)(unsigned, unsigned long *, unsigned long *))
>  {
> -       int ret;
> +       int ret, state;
>
>        ret = gpio_request(template->gpio, template->name);
>        if (ret < 0)
> @@ -92,10 +92,13 @@ static int __devinit create_gpio_led(const struct gpio_led *template,
>                led_dat->cdev.blink_set = gpio_blink_set;
>        }
>        led_dat->cdev.brightness_set = gpio_led_set;
> -       led_dat->cdev.brightness = template->default_state ? LED_FULL : LED_OFF;
> +       if (template->keep_state)
> +               state = !!gpio_get_value(led_dat->gpio) ^ led_dat->active_low;
> +       else
> +               state = template->default_state;
> +       led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;
>
> -       gpio_direction_output(led_dat->gpio,
> -                             led_dat->active_low ^ template->default_state);
> +       gpio_direction_output(led_dat->gpio, led_dat->active_low ^ state);
>
>        INIT_WORK(&led_dat->work, gpio_led_work);
>
> @@ -266,6 +269,7 @@ static int __devinit of_gpio_leds_probe(struct of_device *ofdev,
>                        of_get_property(child, "linux,default-trigger", NULL);
>                state = of_get_property(child, "default-state", NULL);
>                led.default_state = state && !strcmp(state, "on");
> +               led.keep_state = state && !strcmp(state, "keep");
>
>                ret = create_gpio_led(&led, &pdata->led_data[pdata->num_leds++],
>                                      &ofdev->dev, NULL);
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index caa3987..c51b625 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -138,7 +138,8 @@ struct gpio_led {
>        const char *default_trigger;
>        unsigned        gpio;
>        u8              active_low;
> -       u8              default_state;
> +       u8              default_state;  /* 0 = off, 1 = on */
> +       u8              keep_state; /* overrides default_state */
>  };
>
>  struct gpio_led_platform_data {
> --
> 1.5.4.3
>
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.