linux-kernel - [PATCH] leds: leds-gpio: Add a condition check for active low leds.

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Message-Id: <20180905023436.11826-1-songqiang.1304521@gmail.com>
Date:   Wed,  5 Sep 2018 10:34:36 +0800
From:   Song Qiang <songqiang1304521@...il.com>
To:     jacek.anaszewski@...il.com
Cc:     pavel@....cz, robh+dt@...nel.org, mark.rutland@....com,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Song Qiang <songqiang.1304521@...il.com>
Subject: [PATCH] leds: leds-gpio: Add a condition check for active low leds.

Some leds on our board are active low leds, which means these leds
are lighted when the corresponding gpio line is low, while the
original leds-gpio driver default all leds are active high leds.
This patch adds a devicetree node "light-state", whose value should
be "high" for active high leds and "low" for active low leds.
The default value is "high" for compatible for the original driver.

Signed-off-by: Song Qiang <songqiang.1304521@...il.com>
---
 .../devicetree/bindings/leds/leds-gpio.txt    | 15 +++++++++++
 drivers/leds/leds-gpio.c                      | 25 +++++++++++++++++--
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/leds/leds-gpio.txt b/Documentation/devicetree/bindings/leds/leds-gpio.txt
index a48dda268f81..0a8fad75c704 100644
--- a/Documentation/devicetree/bindings/leds/leds-gpio.txt
+++ b/Documentation/devicetree/bindings/leds/leds-gpio.txt
@@ -23,6 +23,9 @@ LED sub-node properties:
   remains up.
 - panic-indicator : (optional)
   see Documentation/devicetree/bindings/leds/common.txt
+- light-state: (optional) Values should be "high" or "low", which indicates
+	the state of the GPIO pin when the led is on.
+  see Documentation/devicetree/bindings/leds/common.txt
 
 Examples:
 
@@ -64,3 +67,15 @@ leds {
 		retain-state-suspended;
 	};
 };
+
+leds {
+	compatible = "gpio-leds";
+
+	led0 {
+		label = "led0";
+		gpios = <&gpio1 19 GPIO_ACTIVE_HIGH>;
+		linux,default-trigger = "heartbeat";
+		default-state = "off";
+		light-state = "low";
+	};
+}
diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
index 764c31301f90..463ded0c71ac 100644
--- a/drivers/leds/leds-gpio.c
+++ b/drivers/leds/leds-gpio.c
@@ -26,9 +26,13 @@ struct gpio_led_data {
 	struct gpio_desc *gpiod;
 	u8 can_sleep;
 	u8 blinking;
+	u8 light_state;
 	gpio_blink_set_t platform_gpio_blink_set;
 };
 
+#define LEDS_GPIO_LIGHTSTATE_HIGH	0
+#define LEDS_GPIO_LIGHTSTATE_LOW	1
+
 static inline struct gpio_led_data *
 			cdev_to_gpio_led_data(struct led_classdev *led_cdev)
 {
@@ -42,9 +46,15 @@ static void gpio_led_set(struct led_classdev *led_cdev,
 	int level;
 
 	if (value == LED_OFF)
-		level = 0;
+		if (led_dat->light_state == LEDS_GPIO_LIGHTSTATE_HIGH)
+			level = 0;
+		else
+			level = 1;
 	else
-		level = 1;
+		if (led_dat->light_state == LEDS_GPIO_LIGHTSTATE_HIGH)
+			level = 1;
+		else
+			level = 0;
 
 	if (led_dat->blinking) {
 		led_dat->platform_gpio_blink_set(led_dat->gpiod, level,
@@ -205,6 +215,17 @@ static struct gpio_leds_priv *gpio_leds_create(struct platform_device *pdev)
 				led.default_state = LEDS_GPIO_DEFSTATE_OFF;
 		}
 
+		if (!fwnode_property_read_string(child, "light-state",
+						 &state)) {
+			if (!strcmp(state, "low"))
+				led_dat->light_state =
+					LEDS_GPIO_LIGHTSTATE_LOW;
+			else{
+				led_dat->light_state =
+					LEDS_GPIO_LIGHTSTATE_HIGH;
+			}
+		}
+
 		if (fwnode_property_present(child, "retain-state-suspended"))
 			led.retain_state_suspended = 1;
 		if (fwnode_property_present(child, "retain-state-shutdown"))
-- 
2.17.1