[PATCH v5 2/3] leds: pwm: add support for default-state device property

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



This patch adds support for "default-state" devicetree property, which
allows to defer pwm init to first use of led.

This allows to configure the PWM early in bootloader to let the LED
blink until an application in Linux userspace sets something different.

Signed-off-by: Denis Osterland-Heim <Denis.Osterland@xxxxxxxxx>
---
 drivers/leds/leds-pwm.c | 54 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c
index ef7b91bd2064..7b199c151768 100644
--- a/drivers/leds/leds-pwm.c
+++ b/drivers/leds/leds-pwm.c
@@ -18,10 +18,15 @@
 #include <linux/pwm.h>
 #include <linux/slab.h>
 
+#define LEDS_PWM_DEFSTATE_OFF	0
+#define LEDS_PWM_DEFSTATE_ON	1
+#define LEDS_PWM_DEFSTATE_KEEP	2
+
 struct led_pwm {
 	const char	*name;
 	const char	*default_trigger;
 	u8		active_low;
+	u8		default_state;
 	unsigned int	max_brightness;
 };
 
@@ -88,7 +93,30 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
 
 	led_data->cdev.brightness_set_blocking = led_pwm_set;
 
-	pwm_init_state(led_data->pwm, &led_data->pwmstate);
+	/* init PWM state */
+	if (led->default_state == LEDS_PWM_DEFSTATE_KEEP) {
+		pwm_get_state(led_data->pwm, &led_data->pwmstate);
+		if (!led_data->pwmstate.period) {
+			led->default_state = LEDS_PWM_DEFSTATE_OFF;
+			dev_warn(dev,
+				"failed to read period for %s, default to off",
+				led->name);
+		}
+	}
+	if (led->default_state != LEDS_PWM_DEFSTATE_KEEP)
+		pwm_init_state(led_data->pwm, &led_data->pwmstate);
+
+	/* set brightness */
+	if (led->default_state == LEDS_PWM_DEFSTATE_ON)
+		led_data->cdev.brightness = led->max_brightness;
+	else if (led->default_state == LEDS_PWM_DEFSTATE_KEEP) {
+		uint64_t brightness;
+
+		brightness = led->max_brightness;
+		brightness *= led_data->pwmstate.duty_cycle;
+		do_div(brightness, led_data->pwmstate.period);
+		led_data->cdev.brightness = brightness;
+	}
 
 	ret = devm_led_classdev_register(dev, &led_data->cdev);
 	if (ret) {
@@ -97,11 +125,13 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
 		return ret;
 	}
 
-	ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
-	if (ret) {
-		dev_err(dev, "failed to set led PWM value for %s: %d",
-			led->name, ret);
-		return ret;
+	if (led->default_state != LEDS_PWM_DEFSTATE_KEEP) {
+		ret = led_pwm_set(&led_data->cdev, led_data->cdev.brightness);
+		if (ret) {
+			dev_err(dev, "failed to set led PWM value for %s: %d",
+				led->name, ret);
+			return ret;
+		}
 	}
 
 	priv->num_leds++;
@@ -117,6 +147,8 @@ static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
 	memset(&led, 0, sizeof(led));
 
 	device_for_each_child_node(dev, fwnode) {
+		const char *state = NULL;
+
 		ret = fwnode_property_read_string(fwnode, "label", &led.name);
 		if (ret && is_of_node(fwnode))
 			led.name = to_of_node(fwnode)->name;
@@ -134,6 +166,16 @@ static int led_pwm_create_fwnode(struct device *dev, struct led_pwm_priv *priv)
 		fwnode_property_read_u32(fwnode, "max-brightness",
 					 &led.max_brightness);
 
+		if (!fwnode_property_read_string(fwnode, "default-state",
+						 &state)) {
+			if (!strcmp(state, "keep"))
+				led.default_state = LEDS_PWM_DEFSTATE_KEEP;
+			else if (!strcmp(state, "on"))
+				led.default_state = LEDS_PWM_DEFSTATE_ON;
+			else
+				led.default_state = LEDS_PWM_DEFSTATE_OFF;
+		}
+
 		ret = led_pwm_add(dev, priv, &led, fwnode);
 		if (ret) {
 			fwnode_handle_put(fwnode);
-- 
2.26.2



Diehl Connectivity Solutions GmbH
Geschäftsführung: Horst Leonberger
Sitz der Gesellschaft: Nürnberg - Registergericht: Amtsgericht
Nürnberg: HRB 32315
___________________________________________________________________________________________________

Der Inhalt der vorstehenden E-Mail ist nicht rechtlich bindend. Diese E-Mail enthaelt vertrauliche und/oder rechtlich geschuetzte Informationen.
Informieren Sie uns bitte, wenn Sie diese E-Mail faelschlicherweise erhalten haben. Bitte loeschen Sie in diesem Fall die Nachricht.
Jede unerlaubte Form der Reproduktion, Bekanntgabe, Aenderung, Verteilung und/oder Publikation dieser E-Mail ist strengstens untersagt.
- Informationen zum Datenschutz, insbesondere zu Ihren Rechten, erhalten Sie unter https://www.diehl.com/group/de/transparenz-und-informationspflichten/

The contents of the above mentioned e-mail is not legally binding. This e-mail contains confidential and/or legally protected information. Please inform us if you have received this e-mail by
mistake and delete it in such a case. Each unauthorized reproduction, disclosure, alteration, distribution and/or publication of this e-mail is strictly prohibited. 
- For general information on data protection and your respective rights please visit https://www.diehl.com/group/en/transparency-and-information-obligations/




[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]


  Powered by Linux