linux-kernel - [PATCH v10 3/5] backlight: gpio: add support for multiple GPIOs for backlight control

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20251230130227.3503590-4-tessolveupstream@gmail.com>
Date: Tue, 30 Dec 2025 18:32:25 +0530
From: Sudarshan Shetty <tessolveupstream@...il.com>
To: andersson@...nel.org,
	konradybcio@...nel.org
Cc: robh@...nel.org,
	krzk+dt@...nel.org,
	conor+dt@...nel.org,
	linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Sudarshan Shetty <tessolveupstream@...il.com>
Subject: [PATCH v10 3/5] backlight: gpio: add support for multiple GPIOs for backlight control

Extend the gpio-backlight driver to handle multiple GPIOs instead of a
single one. This allows panels that require driving several enable pins
to be controlled by the backlight framework.

Signed-off-by: Sudarshan Shetty <tessolveupstream@...il.com>
---
 drivers/video/backlight/gpio_backlight.c | 61 +++++++++++++++++-------
 1 file changed, 45 insertions(+), 16 deletions(-)

diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c
index 728a546904b0..037e1c111e48 100644
--- a/drivers/video/backlight/gpio_backlight.c
+++ b/drivers/video/backlight/gpio_backlight.c
@@ -17,14 +17,18 @@
 
 struct gpio_backlight {
 	struct device *dev;
-	struct gpio_desc *gpiod;
+	struct gpio_desc **gpiods;
+	unsigned int num_gpios;
 };
 
 static int gpio_backlight_update_status(struct backlight_device *bl)
 {
 	struct gpio_backlight *gbl = bl_get_data(bl);
+	unsigned int i;
+	int br = backlight_get_brightness(bl);
 
-	gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl));
+	for (i = 0; i < gbl->num_gpios; i++)
+		gpiod_set_value_cansleep(gbl->gpiods[i], br);
 
 	return 0;
 }
@@ -52,6 +56,7 @@ static int gpio_backlight_probe(struct platform_device *pdev)
 	struct backlight_device *bl;
 	struct gpio_backlight *gbl;
 	int ret, init_brightness, def_value;
+	unsigned int i;
 
 	gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
 	if (gbl == NULL)
@@ -62,10 +67,22 @@ static int gpio_backlight_probe(struct platform_device *pdev)
 
 	def_value = device_property_read_bool(dev, "default-on");
 
-	gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS);
-	if (IS_ERR(gbl->gpiod))
-		return dev_err_probe(dev, PTR_ERR(gbl->gpiod),
-				     "The gpios parameter is missing or invalid\n");
+	gbl->num_gpios = gpiod_count(dev, NULL);
+	if (gbl->num_gpios == 0)
+		return dev_err_probe(dev, -EINVAL,
+			"The gpios parameter is missing or invalid\n");
+	gbl->gpiods = devm_kcalloc(dev, gbl->num_gpios, sizeof(*gbl->gpiods),
+				   GFP_KERNEL);
+	if (!gbl->gpiods)
+		return -ENOMEM;
+
+	for (i = 0; i < gbl->num_gpios; i++) {
+		gbl->gpiods[i] =
+			devm_gpiod_get_index(dev, NULL, i, GPIOD_ASIS);
+		if (IS_ERR(gbl->gpiods[i]))
+			return dev_err_probe(dev, PTR_ERR(gbl->gpiods[i]),
+					"Failed to get GPIO at index %u\n", i);
+	}
 
 	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_RAW;
@@ -78,22 +95,34 @@ static int gpio_backlight_probe(struct platform_device *pdev)
 	}
 
 	/* Set the initial power state */
-	if (!of_node || !of_node->phandle)
+	if (!of_node || !of_node->phandle) {
 		/* Not booted with device tree or no phandle link to the node */
 		bl->props.power = def_value ? BACKLIGHT_POWER_ON
-					    : BACKLIGHT_POWER_OFF;
-	else if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
-		bl->props.power = BACKLIGHT_POWER_OFF;
-	else
-		bl->props.power = BACKLIGHT_POWER_ON;
+						    : BACKLIGHT_POWER_OFF;
+	} else {
+		bool all_high = true;
+
+		for (i = 0; i < gbl->num_gpios; i++) {
+			if (gpiod_get_value_cansleep(gbl->gpiods[i]) != 0) {
+				all_high = false;
+				break;
+			}
+		}
+
+		bl->props.power =
+			all_high ? BACKLIGHT_POWER_ON :  BACKLIGHT_POWER_OFF;
+	}
 
 	bl->props.brightness = 1;
 
 	init_brightness = backlight_get_brightness(bl);
-	ret = gpiod_direction_output(gbl->gpiod, init_brightness);
-	if (ret) {
-		dev_err(dev, "failed to set initial brightness\n");
-		return ret;
+
+	for (i = 0; i < gbl->num_gpios; i++) {
+		ret = gpiod_direction_output(gbl->gpiods[i], init_brightness);
+		if (ret)
+			return dev_err_probe(dev, ret,
+					"failed to set gpio %u direction\n",
+					i);
 	}
 
 	platform_set_drvdata(pdev, bl);
-- 
2.34.1