drivers: led: lp5569: implement write_channels api

The lp5569 has multiple pwm outputs, and thus implementing the
write_channels api to set multiple values in a single call makes sense.

Implement the write_channels function with a basic range check on the
channel range.
Since the lp5569 supports auto-increment, all of the channels can be
written in one i2c transfer, starting from the pwm register of the
start_channel.

Signed-off-by: Emil Dahl Juhl <emdj@bang-olufsen.dk>

doc/releases/release-notes-4.1.rst

@@ -141,6 +141,7 @@ Drivers and Sensors
 
   * Added a new set of devicetree based LED APIs, see :c:struct:`led_dt_spec`.
   * lp5569: added use of auto-increment functionality.
+  * lp5569: implemented ``write_channels`` api.
 
 * LED Strip
 

drivers/led/lp5569.c

@@ -77,6 +77,23 @@ static inline int lp5569_led_off(const struct device *dev, uint32_t led)
 	return lp5569_led_set_brightness(dev, led, 0);
 }
 
+static int lp5569_write_channels(const struct device *dev, uint32_t start_channel,
+				 uint32_t num_channels, const uint8_t *buf)
+{
+	const struct lp5569_config *config = dev->config;
+	uint32_t i2c_len = num_channels + 1;
+	uint8_t i2c_msg[LP5569_NUM_LEDS + 1];
+
+	if ((uint64_t)start_channel + num_channels > LP5569_NUM_LEDS) {
+		return -EINVAL;
+	}
+
+	i2c_msg[0] = LP5569_LED0_PWM + start_channel;
+	memcpy(&i2c_msg[1], buf, num_channels);
+
+	return i2c_write_dt(&config->bus, i2c_msg, i2c_len);
+}
+
 static int lp5569_enable(const struct device *dev)
 {
 	const struct lp5569_config *config = dev->config;
@@ -170,6 +187,7 @@ static const struct led_driver_api lp5569_led_api = {
 	.set_brightness = lp5569_led_set_brightness,
 	.on = lp5569_led_on,
 	.off = lp5569_led_off,
+	.write_channels = lp5569_write_channels,
 };
 
 #define LP5569_DEFINE(id)                                                                          \