On Wed, 24 Mar 2021 15:56:30 +0800
Hermes Zhang [off-list ref] wrote:

From: Hermes Zhang <redacted>

Introduce a new multiple GPIOs LED driver. This LED will made of
multiple GPIOs (up to 8) and will map different brightness to different
GPIOs states which defined in dts file.

I wonder how many boards have such LEDs.

Also if it wouldn't be better to expand the original leds-gpio driver.
Probably depends on how much larger would such expansion make the
leds-gpio driver.

+#include <linux/err.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/kernel.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>

Why do you include slab.h?

+
+#define MAX_GPIO_NUM  8
+
+struct multi_gpio_led_priv {
+	struct led_classdev cdev;
+
+	struct gpio_descs *gpios;
+
+	u8 *states;
+	int nr_states;
+};

Use flexible array members. Allocate with
  devm_kzalloc(dev, struct_size(priv, states, priv->nr_states),
               GFP_KERNEL)

+
+
+static void multi_gpio_led_set(struct led_classdev *led_cdev,
+	enum led_brightness value)
+{
+	struct multi_gpio_led_priv *priv;
+	int idx;
+
+	DECLARE_BITMAP(values, MAX_GPIO_NUM);
+
+	priv = container_of(led_cdev, struct multi_gpio_led_priv, cdev);
+
+	idx = (value - LED_OFF) * priv->nr_states / (LED_FULL + 1);

LED_FULL / LED_OFF are deprecated, don't use them.

+
+	values[0] = priv->states[idx];
+
+	gpiod_set_array_value(priv->gpios->ndescs, priv->gpios->desc,
+	    priv->gpios->info, values);
+}
+
+static int multi_gpio_led_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct multi_gpio_led_priv *priv = NULL;
+	int ret;
+	const char *state = NULL;
+	struct led_init_data init_data = {};
+
+	priv = devm_kzalloc(dev, sizeof(struct multi_gpio_led_priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->gpios = devm_gpiod_get_array(dev, "led", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->gpios))
+		return PTR_ERR(priv->gpios);
+
+	if (priv->gpios->ndescs >= MAX_GPIO_NUM) {
+		dev_err(dev, "Too many GPIOs\n");
+		return -EINVAL;
+	}
+
+	ret = of_property_count_u8_elems(node, "led-states");
+	if (ret < 0)
+		return ret;
+
+	priv->nr_states = ret;
+	priv->states = devm_kzalloc(dev, sizeof(*priv->states) * priv->nr_states, GFP_KERNEL);
+	if (!priv->states)
+		return -ENOMEM;
+
+	ret = of_property_read_u8_array(node, "led-states", priv->states, priv->nr_states);
+	if (ret)
+		return ret;
+
+	priv->cdev.max_brightness = LED_FULL;

???? max_brightness is not 255 (= LED_FULL). max_brightness must be
derived from the led-states property.

+	priv->cdev.default_trigger = of_get_property(node, "linux,default-trigger", NULL);
+	priv->cdev.brightness_set = multi_gpio_led_set;
+
+	init_data.fwnode = of_fwnode_handle(node);
+
+	ret = devm_led_classdev_register_ext(dev, &priv->cdev, &init_data);
+	if (ret < 0)
+		return ret;
+
+	of_property_read_string(node, "default-state", &state);
+	if (!strcmp(state, "on"))
+		multi_gpio_led_set(&priv->cdev, LED_FULL);
+	else
+		multi_gpio_led_set(&priv->cdev, LED_OFF);

Again LED_FULL and LED_OFF...
What about default-state = "keep" ?

Hermes, do you actually have a device that controls LEDs this way? How
many brightness options do they have?

Also I think this functionality could be easily incorporated into the
existing leds-gpio driver, instead of creating new driver.

Moreover your driver can control only one LED, so it needs to be
probed multiple times for multiple LEDs. Meanwhile the leds-gpio driver
can register multiple LEDs in one probe...

Marek