linux-kernel - Re: LEDs: how to handle gpios that control brightness for all LEDs

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Date:	Sun, 29 Jun 2008 21:59:23 +0200
From:	Martin Michlmayr <tbm@...ius.com>
To:	Riku Voipio <riku.voipio@....fi>
Cc:	Richard Purdie <rpurdie@...ys.net>, linux-kernel@...r.kernel.org,
	buytenh@...tstofly.org
Subject: Re: LEDs: how to handle gpios that control brightness for all LEDs

* Riku Voipio <riku.voipio@....fi> [2008-06-28 20:52]:
> > I have a device that has various gpios that correspond to the colours
> > (blue, red) of various LEDs.  They only accept 0/1, not the actual
> > brightness.  However, there are two other gpios that can be used to
> > control the brightness (of all LEDs): gpio V_LED 5V is bright, gpio
> > V_LED 3.3V is dimmed and if neither of these two gpios are set, all
> > LEDs stay off.
> 
> > Can I simply export these brightness gpios to userland or would it be
> > better to handle the brightness setting in the kernel so that setting
> > e.g. 100 to a LED would automatically set the V_LED 3.3V gpio and 255
> > would set V_LED 5V.  If so, how should this be done?
> 
> There is a enum led_brightness, which defines LED_HALF and LED_FULL. You
> would need a custom brightness function. Leds-gpio driver would need to
> be extended for it. The main problem with this approach is the
> unexpected effect for enduser, that adjusting brighntess of one led
> affects all of them.

OK, this sounds to me like I should simply export the gpios that
influence the brightness.

> default-on trigger is probably the easiest way.

This works for me, thanks.

New patch below.  Any comments Richard?


diff --git a/arch/arm/mach-orion5x/mv2120-setup.c b/arch/arm/mach-orion5x/mv2120-setup.c
index d838bdb..0ac5209 100644
--- a/arch/arm/mach-orion5x/mv2120-setup.c
+++ b/arch/arm/mach-orion5x/mv2120-setup.c
@@ -137,6 +137,50 @@ static struct i2c_board_info __initdata mv2120_i2c_rtc = {
 	.irq	= 0,
 };
 
+static struct gpio_led mv2120_led_pins[] = {
+	{
+		.name			= "mv2120:blue:health",
+		.gpio			= 0,
+	},
+	{
+		.name			= "mv2120:red:health",
+		.gpio			= 1,
+	},
+	{
+		.name			= "mv2120:led:bright",
+		.gpio			= 4,
+		.default_trigger	= "default-on",
+	},
+	{
+		.name			= "mv2120:led:dimmed",
+		.gpio			= 5,
+	},
+	{
+		.name			= "mv2120:red:sata0",
+		.gpio			= 8,
+		.active_low		= 1,
+	},
+	{
+		.name			= "mv2120:red:sata1",
+		.gpio			= 9,
+		.active_low		= 1,
+	},
+
+};
+
+static struct gpio_led_platform_data mv2120_led_data = {
+	.leds		= mv2120_led_pins,
+	.num_leds	= ARRAY_SIZE(mv2120_led_pins),
+};
+
+static struct platform_device mv2120_leds = {
+	.name	= "leds-gpio",
+	.id	= -1,
+	.dev	= {
+		.platform_data	= &mv2120_led_data,
+	}
+};
+
 static void mv2120_power_off(void)
 {
 	pr_info("%s: triggering power-off...\n", __func__);
@@ -172,6 +216,7 @@ static void __init mv2120_init(void)
 			gpio_free(MV2120_GPIO_RTC_IRQ);
 	}
 	i2c_register_board_info(0, &mv2120_i2c_rtc, 1);
+	platform_device_register(&mv2120_leds);
 
 	/* register mv2120 specific power-off method */
 	if (gpio_request(MV2120_GPIO_POWER_OFF, "POWEROFF") != 0 ||

-- 
Martin Michlmayr
http://www.cyrius.com/
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