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SubjectRe: [PATCH 4/4] leds: Let GPIO LEDs keep their current state
On Mon, 17 Nov 2008, Richard Purdie wrote:
> On Fri, 2008-10-24 at 16:09 -0700, Trent Piepho wrote:
>> + if (template->keep_state)
>> + state = !!gpio_get_value(led_dat->gpio) ^ led_dat->active_low;
>> + else
>> + state = template->default_state;
>>
>> state = of_get_property(child, "default-state", NULL);
>> led.default_state = state && !strcmp(state, "on");
>> + led.keep_state = state && !strcmp(state, "keep");
>>
>> +++ 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 */
>> };
>
> How about something simpler here, just make default state have three
> different values - "keep", "on" and "off"? I'm not keen on having two
> different state variables like this.

I thought of that, but it ends up being more complex. Instead of just
using:
static const struct gpio_led myled = {
.name = "something",
.keep_state = 1,
}

You'd do something like this:
.default_state = LEDS_GPIO_DEFSTATE_KEEP,

Is that better? The constants for on/off/keep are one more thing you have
to look-up and remember when defining leds. The code in the leds-gpio
driver ends up getting more complex to deal with one tristate vs two
booleans.

This is a patch to change to a tristate. I don't think it's an
improvement. More symbols defined, more code, extra stuff to remember
when defining leds, and removing the field from struct gpio_led doesn't
make it smaller due to padding.

diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
index bb2a234..8a7303c 100644
--- a/drivers/leds/leds-gpio.c
+++ b/drivers/leds/leds-gpio.c
@@ -92,10 +92,10 @@ 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;
- if (template->keep_state)
+ if (template->default_state == LEDS_GPIO_DEFSTATE_KEEP)
state = !!gpio_get_value(led_dat->gpio) ^ led_dat->active_low;
else
- state = template->default_state;
+ state = (template->default_state == LEDS_GPIO_DEFSTATE_ON);
led_dat->cdev.brightness = state ? LED_FULL : LED_OFF;

gpio_direction_output(led_dat->gpio, led_dat->active_low ^ state);
@@ -268,8 +268,15 @@ static int __devinit of_gpio_leds_probe(struct of_device *ofdev,
led.default_trigger =
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");
+ if (state) {
+ if (!strcmp(state, "keep")) {
+ led.default_state = LEDS_GPIO_DEFSTATE_KEEP;
+ } else if(!strcmp(state, "on")) {
+ led.default_state = LEDS_GPIO_DEFSTATE_ON;
+ } else {
+ led.default_state = LEDS_GPIO_DEFSTATE_OFF;
+ }
+ }

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 c51b625..f4a125c 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -138,9 +138,12 @@ struct gpio_led {
const char *default_trigger;
unsigned gpio;
u8 active_low;
- u8 default_state; /* 0 = off, 1 = on */
- u8 keep_state; /* overrides default_state */
+ u8 default_state;
+ /* default_state should be one of LEDS_GPIO_DEFSTATE_(ON|OFF|KEEP) */
};
+#define LEDS_GPIO_DEFSTATE_OFF 0
+#define LEDS_GPIO_DEFSTATE_ON 1
+#define LEDS_GPIO_DEFSTATE_KEEP 2

struct gpio_led_platform_data {
int num_leds;

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