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// SPDX-License-Identifier: GPL-2.0
/*
* Multi-color LED built with monochromatic LED devices
*
* This driver groups several monochromatic LED devices in a single multicolor LED device.
*
* Compared to handling this grouping in user-space, the benefits are:
* - The state of the monochromatic LED relative to each other is always consistent.
* - The sysfs interface of the LEDs can be used for the group as a whole.
*
* Copyright 2023 Jean-Jacques Hiblot <jjhiblot@traphandler.com>
*/
#include <linux/err.h>
#include <linux/leds.h>
#include <linux/led-class-multicolor.h>
#include <linux/math.h>
#include <linux/module.h>
#include <linux/mod_devicetable.h>
#include <linux/platform_device.h>
#include <linux/property.h>
struct leds_multicolor {
struct led_classdev_mc mc_cdev;
struct led_classdev **monochromatics;
};
static int leds_gmc_set(struct led_classdev *cdev, enum led_brightness brightness)
{
struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
struct leds_multicolor *priv = container_of(mc_cdev, struct leds_multicolor, mc_cdev);
const unsigned int group_max_brightness = mc_cdev->led_cdev.max_brightness;
int i;
for (i = 0; i < mc_cdev->num_colors; i++) {
struct led_classdev *mono = priv->monochromatics[i];
const unsigned int mono_max_brightness = mono->max_brightness;
unsigned int intensity = mc_cdev->subled_info[i].intensity;
int mono_brightness;
/*
* Scale the brightness according to relative intensity of the
* color AND the max brightness of the monochromatic LED.
*/
mono_brightness = DIV_ROUND_CLOSEST(brightness * intensity * mono_max_brightness,
group_max_brightness * group_max_brightness);
led_set_brightness(mono, mono_brightness);
}
return 0;
}
static void restore_sysfs_write_access(void *data)
{
struct led_classdev *led_cdev = data;
/* Restore the write acccess to the LED */
mutex_lock(&led_cdev->led_access);
led_sysfs_enable(led_cdev);
mutex_unlock(&led_cdev->led_access);
}
static int leds_gmc_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct led_init_data init_data = {};
struct led_classdev *cdev;
struct mc_subled *subled;
struct leds_multicolor *priv;
unsigned int max_brightness = 0;
int i, ret, count = 0;
priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
for (;;) {
struct led_classdev *led_cdev;
led_cdev = devm_of_led_get_optional(dev, count);
if (IS_ERR(led_cdev))
return dev_err_probe(dev, PTR_ERR(led_cdev), "Unable to get LED #%d",
count);
if (!led_cdev)
break;
priv->monochromatics = devm_krealloc_array(dev, priv->monochromatics,
count + 1, sizeof(*priv->monochromatics),
GFP_KERNEL);
if (!priv->monochromatics)
return -ENOMEM;
priv->monochromatics[count] = led_cdev;
max_brightness = max(max_brightness, led_cdev->max_brightness);
count++;
}
subled = devm_kcalloc(dev, count, sizeof(*subled), GFP_KERNEL);
if (!subled)
return -ENOMEM;
priv->mc_cdev.subled_info = subled;
for (i = 0; i < count; i++) {
struct led_classdev *led_cdev = priv->monochromatics[i];
subled[i].color_index = led_cdev->color;
/* Configure the LED intensity to its maximum */
subled[i].intensity = max_brightness;
}
/* Initialise the multicolor's LED class device */
cdev = &priv->mc_cdev.led_cdev;
cdev->flags = LED_CORE_SUSPENDRESUME;
cdev->brightness_set_blocking = leds_gmc_set;
cdev->max_brightness = max_brightness;
cdev->color = LED_COLOR_ID_MULTI;
priv->mc_cdev.num_colors = count;
init_data.fwnode = dev_fwnode(dev);
ret = devm_led_classdev_multicolor_register_ext(dev, &priv->mc_cdev, &init_data);
if (ret)
return dev_err_probe(dev, ret, "failed to register multicolor LED for %s.\n",
cdev->name);
ret = leds_gmc_set(cdev, cdev->brightness);
if (ret)
return dev_err_probe(dev, ret, "failed to set LED value for %s.", cdev->name);
for (i = 0; i < count; i++) {
struct led_classdev *led_cdev = priv->monochromatics[i];
/*
* Make the individual LED sysfs interface read-only to prevent the user
* to change the brightness of the individual LEDs of the group.
*/
mutex_lock(&led_cdev->led_access);
led_sysfs_disable(led_cdev);
mutex_unlock(&led_cdev->led_access);
/* Restore the write access to the LED sysfs when the group is destroyed */
devm_add_action_or_reset(dev, restore_sysfs_write_access, led_cdev);
}
return 0;
}
static const struct of_device_id of_leds_group_multicolor_match[] = {
{ .compatible = "leds-group-multicolor" },
{}
};
MODULE_DEVICE_TABLE(of, of_leds_group_multicolor_match);
static struct platform_driver leds_group_multicolor_driver = {
.probe = leds_gmc_probe,
.driver = {
.name = "leds_group_multicolor",
.of_match_table = of_leds_group_multicolor_match,
}
};
module_platform_driver(leds_group_multicolor_driver);
MODULE_AUTHOR("Jean-Jacques Hiblot <jjhiblot@traphandler.com>");
MODULE_DESCRIPTION("LEDs group multicolor driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:leds-group-multicolor");
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