linux-kernel - [PATCH 2/2] leds: syscon: Implement support for active-low property

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Date:   Thu, 18 Aug 2022 19:25:28 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Marek Behún <kabel@...nel.org>
Cc:     linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] leds: syscon: Implement support for active-low property

This new active-low property specify that LED has inverted logic
(0 - enable LED, 1 - disable LED).

Signed-off-by: Pali Rohár <pali@...nel.org>
---
 drivers/leds/leds-syscon.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/leds/leds-syscon.c b/drivers/leds/leds-syscon.c
index 7eddb8ecb44e..5e605d8438e9 100644
--- a/drivers/leds/leds-syscon.c
+++ b/drivers/leds/leds-syscon.c
@@ -29,6 +29,7 @@ struct syscon_led {
 	struct regmap *map;
 	u32 offset;
 	u32 mask;
+	bool active_low;
 	bool state;
 };
 
@@ -41,10 +42,10 @@ static void syscon_led_set(struct led_classdev *led_cdev,
 	int ret;
 
 	if (value == LED_OFF) {
-		val = 0;
+		val = sled->active_low ? sled->mask : 0;
 		sled->state = false;
 	} else {
-		val = sled->mask;
+		val = sled->active_low ? 0 : sled->mask;
 		sled->state = true;
 	}
 
@@ -85,6 +86,8 @@ static int syscon_led_probe(struct platform_device *pdev)
 		return -EINVAL;
 	if (of_property_read_u32(np, "mask", &sled->mask))
 		return -EINVAL;
+	if (of_find_property(np, "active-low", NULL))
+		sled->active_low = true;
 
 	state = of_get_property(np, "default-state", NULL);
 	if (state) {
@@ -95,17 +98,20 @@ static int syscon_led_probe(struct platform_device *pdev)
 			if (ret < 0)
 				return ret;
 			sled->state = !!(val & sled->mask);
+			if (sled->active_low)
+				sled->state = !sled->state;
 		} else if (!strcmp(state, "on")) {
 			sled->state = true;
 			ret = regmap_update_bits(map, sled->offset,
 						 sled->mask,
-						 sled->mask);
+						 sled->active_low ? 0 : sled->mask);
 			if (ret < 0)
 				return ret;
 		} else {
 			sled->state = false;
 			ret = regmap_update_bits(map, sled->offset,
-						 sled->mask, 0);
+						 sled->mask,
+						 sled->active_low ? sled->mask : 0);
 			if (ret < 0)
 				return ret;
 		}
-- 
2.20.1