[PATCH 2/4] backlight: ktz8866: add slave handler

[Pengyu Luo <mitltlatltl@gmail.com>]

Kinetic ktz8866, found in many android devices, nowadays, some oem use
dual ktz8866 to support a larger panel and  higher brightness, original
driver would only handle half backlight region on these devices,
registering it twice is unreasonable, so adding the slave handler to
support it.

Note that, none of the devices supported by upstream require this, the
devices using this is porting.

Signed-off-by: Pengyu Luo <mitltlatltl@gmail.com>
---
 drivers/video/backlight/ktz8866.c | 68 +++++++++++++++++++++++++++----
 1 file changed, 59 insertions(+), 9 deletions(-)

diff --git a/drivers/video/backlight/ktz8866.c b/drivers/video/backlight/ktz8866.c
index 351c2b4d6..017ad80dd 100644
--- a/drivers/video/backlight/ktz8866.c
+++ b/drivers/video/backlight/ktz8866.c
@@ -3,6 +3,9 @@
  * Backlight driver for the Kinetic KTZ8866
  *
  * Copyright (C) 2022, 2023 Jianhua Lu <lujianhua000@gmail.com>
+ *
+ * Apr 2025 - Pengyu Luo <mitltlatltl@gmail.com>
+ *	Added handling for dual KTZ8866(master and slave)
  */
 
 #include <linux/backlight.h>
@@ -43,11 +46,17 @@
 #define LCD_BIAS_EN 0x9F
 #define PWM_HYST 0x5
 
+struct ktz8866_slave {
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
 struct ktz8866 {
 	struct i2c_client *client;
 	struct regmap *regmap;
-	bool led_on;
 	struct gpio_desc *enable_gpio;
+	struct ktz8866_slave *slave;
+	bool led_on;
 };
 
 static const struct regmap_config ktz8866_regmap_config = {
@@ -56,16 +65,22 @@ static const struct regmap_config ktz8866_regmap_config = {
 	.max_register = REG_MAX,
 };
 
-static int ktz8866_write(struct ktz8866 *ktz, unsigned int reg,
-			 unsigned int val)
+static void ktz8866_write(struct ktz8866 *ktz, unsigned int reg,
+			  unsigned int val)
 {
-	return regmap_write(ktz->regmap, reg, val);
+	regmap_write(ktz->regmap, reg, val);
+
+	if (ktz->slave)
+		regmap_write(ktz->slave->regmap, reg, val);
 }
 
-static int ktz8866_update_bits(struct ktz8866 *ktz, unsigned int reg,
-			       unsigned int mask, unsigned int val)
+static void ktz8866_update_bits(struct ktz8866 *ktz, unsigned int reg,
+				unsigned int mask, unsigned int val)
 {
-	return regmap_update_bits(ktz->regmap, reg, mask, val);
+	regmap_update_bits(ktz->regmap, reg, mask, val);
+
+	if (ktz->slave)
+		regmap_update_bits(ktz->slave->regmap, reg, mask, val);
 }
 
 static int ktz8866_backlight_update_status(struct backlight_device *backlight_dev)
@@ -124,10 +139,41 @@ static void ktz8866_init(struct ktz8866 *ktz)
 		ktz8866_write(ktz, LCD_BIAS_CFG1, LCD_BIAS_EN);
 }
 
+static int ktz8866_slave_register(struct ktz8866 *ktz)
+{
+	struct device *dev = &ktz->client->dev;
+	struct ktz8866_slave *slave;
+	struct i2c_client *client;
+	struct device_node *np;
+
+	np = of_find_compatible_node(NULL, NULL, "kinetic,ktz8866-slave");
+	if (!np)
+		return 0;
+
+	client = of_find_i2c_device_by_node(np);
+	of_node_put(np);
+	if (!client)
+		return 0;
+
+	slave = devm_kzalloc(dev, sizeof(*slave), GFP_KERNEL);
+	if (!slave)
+		return -ENOMEM;
+
+	slave->client = client;
+	slave->regmap = devm_regmap_init_i2c(client, &ktz8866_regmap_config);
+	if (IS_ERR(slave->regmap))
+		return dev_err_probe(&client->dev, PTR_ERR(slave->regmap),
+				     "failed to init regmap\n");
+
+	ktz->slave = slave;
+
+	return 0;
+}
+
 static int ktz8866_probe(struct i2c_client *client)
 {
 	struct backlight_device *backlight_dev;
-	struct backlight_properties props;
+	struct backlight_properties props = {};
 	struct ktz8866 *ktz;
 	int ret = 0;
 
@@ -151,7 +197,6 @@ static int ktz8866_probe(struct i2c_client *client)
 	if (IS_ERR(ktz->enable_gpio))
 		return PTR_ERR(ktz->enable_gpio);
 
-	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_RAW;
 	props.max_brightness = MAX_BRIGHTNESS;
 	props.brightness = DEFAULT_BRIGHTNESS;
@@ -163,6 +208,11 @@ static int ktz8866_probe(struct i2c_client *client)
 		return dev_err_probe(&client->dev, PTR_ERR(backlight_dev),
 				"failed to register backlight device\n");
 
+	ret = ktz8866_slave_register(ktz);
+	if (ret)
+		return dev_err_probe(&client->dev, ret,
+				     "failed to register slave\n");
+
 	ktz8866_init(ktz);
 
 	i2c_set_clientdata(client, backlight_dev);
-- 
2.49.0