[PATCH 0/1] leds: Introduce the multi_max_intensity sysfs attribute

[PATCH 0/1] leds: Introduce the multi_max_intensity sysfs attribute

[Armin Wolf]

This patch series was born out of of a mailing list thread [1] where
i asked how to properly model a RGB LED as a multicolor LED. Said
LED has some exotic properties:

1. 5 global brightness levels.
2. 50 intensity levels for each R/G/B color components.

The current sysfs interface mandates that the maximum intensity value
for each color component should be the same as the maximum global
brightness. This makes sense for LEDs that only emulate global
brightness using led_mc_calc_color_components(), but causes problems
for LEDs that perform global brightness control in hardware.

Faking a maximum global brightness of 50 will not work in this case,
as the hardware can change the global brightness on its own. Userspace
applications might also prefer to know the true maximum brightness
value.

Because of this i decided to add a new sysfs attribute called
"multi_max_intensity". This attribute is similar to the
"max_brightness" sysfs attribute, except that it targets the intensity
values inside the "multi_intensity" sysfs atribute. I also decided to 
cap intensity values comming from userspace to said maximum intensity
values to relieve drivers from doing it themself. This was already
proposed in a unrelated patch [2] and might break some misbehaving
userspace applications that do not respect max_brightness.

I tested the new sysfs attribute using a custom kernel module:

#include <linux/module.h>
#include <linux/init.h>
#include <linux/led-class-multicolor.h>

static int test_brightness_set_blocking(struct led_classdev *led_cdev,
					enum led_brightness brightness)
{
	struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(led_cdev);

	for (int i = 0; i < mc_cdev->num_colors; i++) {
		if (mc_cdev->subled_info[i].intensity > 30)
			return -EIO;
	}

	return 0;
}

static struct mc_subled subleds[] = {
	{
		.color_index = LED_COLOR_ID_RED,
		.max_intensity = 0,
		.channel = 1,
	},
	{
		.color_index = LED_COLOR_ID_GREEN,
		.max_intensity = 0,
		.channel = 2,
	},
	{
		.color_index = LED_COLOR_ID_BLUE,
		.max_intensity = 0,
		.channel = 3,
	},
};

static struct led_classdev_mc led_mc_cdev = {
	.led_cdev = {
		.max_brightness = 255,
		.color = LED_COLOR_ID_MULTI,
		.flags = LED_CORE_SUSPENDRESUME | LED_REJECT_NAME_CONFLICT,
		.brightness_set_blocking = test_brightness_set_blocking,
	},
	.num_colors = ARRAY_SIZE(subleds),
	.subled_info = subleds,
};

static int __init test_init(void)
{
	struct led_init_data init_data = {
		.devicename = "test-led",
		.default_label = "multicolor:" LED_FUNCTION_KBD_BACKLIGHT,
		.devname_mandatory = true,
	};

	return led_classdev_multicolor_register_ext(NULL, &led_mc_cdev, &init_data);
}
module_init(test_init);

static void __exit test_exit(void)
{
	led_classdev_multicolor_unregister(&led_mc_cdev);
}
module_exit(test_exit);

MODULE_AUTHOR("Armin Wolf <W_Armin@gmx.de>");
MODULE_DESCRIPTION("Multicolor LED test device");
MODULE_LICENSE("GPL");

[1] https://lore.kernel.org/linux-leds/2d91a44e-fce2-42dc-b529-133ab4a191f0@gmx.de/
[2] https://lore.kernel.org/linux-leds/20260123-leds-multicolor-limit-intensity-v1-1-b37761c2fdfd@pengutronix.de/

Changes since RFC:
- rework documentation
- drop useless defines
- reduce amount of driver code churn

Armin Wolf (1):
  leds: Introduce the multi_max_intensity sysfs attribute

 .../ABI/testing/sysfs-class-led-multicolor    | 19 ++++++--
 Documentation/leds/leds-class-multicolor.rst  | 21 ++++++++-
 drivers/leds/led-class-multicolor.c           | 47 ++++++++++++++++++-
 drivers/leds/leds-lp50xx.c                    |  1 +
 drivers/leds/rgb/leds-ncp5623.c               |  4 +-
 include/linux/led-class-multicolor.h          | 30 +++++++++++-
 6 files changed, 113 insertions(+), 9 deletions(-)

-- 
2.39.5

[PATCH 1/1] leds: Introduce the multi_max_intensity sysfs attribute

[Armin Wolf]

Some multicolor LEDs support global brightness control in hardware,
meaning that the maximum intensity of the color components is not
connected to the maximum global brightness. Such LEDs cannot be
described properly by the current multicolor LED class interface,
because it assumes that the maximum intensity of each color component
is described by the maximum global brightness of the LED.

Fix this by introducing a new sysfs attribute called
"multi_max_intensity" holding the maximum intensity values for the
color components of a multicolor LED class device. Drivers can use
the new max_intensity field inside struct mc_subled to tell the
multicolor LED class code about those values. Intensity values written
by userspace applications will be limited to this maximum value.

Drivers for multicolor LEDs that do not support global brightness
control in hardware might still want to use the maximum global LED
brightness supplied via devicetree as the maximum intensity of each
individual color component. Such drivers should set max_intensity
to 0 so that the multicolor LED core can act accordingly.

The lp50xx and ncp5623 LED drivers already use hardware-based control
for the global LED brightness. Modify those drivers to correctly
initalize .max_intensity to avoid being limited to the maximum global
brightness supplied via devicetree.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
---
 .../ABI/testing/sysfs-class-led-multicolor    | 19 ++++++--
 Documentation/leds/leds-class-multicolor.rst  | 21 ++++++++-
 drivers/leds/led-class-multicolor.c           | 47 ++++++++++++++++++-
 drivers/leds/leds-lp50xx.c                    |  1 +
 drivers/leds/rgb/leds-ncp5623.c               |  4 +-
 include/linux/led-class-multicolor.h          | 30 +++++++++++-
 6 files changed, 113 insertions(+), 9 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
index 16fc827b10cb..197da3e775b4 100644
--- a/Documentation/ABI/testing/sysfs-class-led-multicolor
+++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
@@ -16,9 +16,22 @@ Date:		March 2020
 KernelVersion:	5.9
 Contact:	Dan Murphy <dmurphy@ti.com>
 Description:	read/write
-		This file contains array of integers. Order of components is
-		described by the multi_index array. The maximum intensity should
-		not exceed /sys/class/leds/<led>/max_brightness.
+		This file contains an array of integers. The order of components
+		is described by the multi_index array. The maximum intensity value
+		supported by each color component is described by the multi_max_intensity
+		file. Writing intensity values larger than the maximum value of a
+		given color component will result in those values being clamped.
+
+		For additional details please refer to
+		Documentation/leds/leds-class-multicolor.rst.
+
+What:		/sys/class/leds/<led>/multi_max_intensity
+Date:		March 2026
+KernelVersion:	7.1
+Contact:	Armin Wolf <W_Armin@gmx.de>
+Description:	read
+		This file contains an array of integers describing the maximum
+		intensity value for each intensity component.
 
 		For additional details please refer to
 		Documentation/leds/leds-class-multicolor.rst.
diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
index c6b47b4093c4..8f42f10078ad 100644
--- a/Documentation/leds/leds-class-multicolor.rst
+++ b/Documentation/leds/leds-class-multicolor.rst
@@ -25,10 +25,14 @@ color name to indexed value.
 The ``multi_index`` file is an array that contains the string list of the colors as
 they are defined in each ``multi_*`` array file.
 
-The ``multi_intensity`` is an array that can be read or written to for the
+The ``multi_intensity`` file is an array that can be read or written to for the
 individual color intensities.  All elements within this array must be written in
 order for the color LED intensities to be updated.
 
+The ``multi_max_intensity`` file is an array that contains the maximum intensity
+value supported by each color intensity. Intensity values above this will be
+automatically clamped into the supported range.
+
 Directory Layout Example
 ========================
 .. code-block:: console
@@ -38,6 +42,7 @@ Directory Layout Example
     -r--r--r--    1 root     root          4096 Oct 19 16:16 max_brightness
     -r--r--r--    1 root     root          4096 Oct 19 16:16 multi_index
     -rw-r--r--    1 root     root          4096 Oct 19 16:16 multi_intensity
+    -r--r--r--    1 root     root          4096 OCt 19 16:16 multi_max_intensity
 
 ..
 
@@ -104,3 +109,17 @@ the color LED group.
     128
 
 ..
+
+Writing intensity values larger than the maximum specified in ``multi_max_intensity``
+will result in those values being clamped into the supported range.
+
+.. code-block:: console
+
+   # cat /sys/class/leds/multicolor:status/multi_max_intensity
+   255 255 255
+
+   # echo 512 512 512 > /sys/class/leds/multicolor:status/multi_intensity
+   # cat /sys/class/leds/multicolor:status/multi_intensity
+   255 255 255
+
+..
diff --git a/drivers/leds/led-class-multicolor.c b/drivers/leds/led-class-multicolor.c
index 6b671f3f9c61..13a35e6a28df 100644
--- a/drivers/leds/led-class-multicolor.c
+++ b/drivers/leds/led-class-multicolor.c
@@ -7,10 +7,28 @@
 #include <linux/init.h>
 #include <linux/led-class-multicolor.h>
 #include <linux/math.h>
+#include <linux/minmax.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 
+static unsigned int led_mc_get_max_intensity(struct led_classdev_mc *mcled_cdev, size_t index)
+{
+	unsigned int max_intensity;
+
+	/* The maximum global brightness value might still be changed by
+	 * led_classdev_register_ext() using devicetree properties. This
+	 * prevents us from changing subled_info[X].max_intensity when
+	 * registering a multicolor LED class device, so we have to do
+	 * this during runtime.
+	 */
+	max_intensity = mcled_cdev->subled_info[index].max_intensity;
+	if (max_intensity)
+		return max_intensity;
+
+	return mcled_cdev->led_cdev.max_brightness;
+}
+
 int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
 				 enum led_brightness brightness)
 {
@@ -27,6 +45,27 @@ int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
 }
 EXPORT_SYMBOL_GPL(led_mc_calc_color_components);
 
+static ssize_t multi_max_intensity_show(struct device *dev,
+					struct device_attribute *intensity_attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
+	unsigned int max_intensity;
+	int len = 0;
+	int i;
+
+	for (i = 0; i < mcled_cdev->num_colors; i++) {
+		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
+		len += sprintf(buf + len, "%u", max_intensity);
+		if (i < mcled_cdev->num_colors - 1)
+			len += sprintf(buf + len, " ");
+	}
+
+	buf[len++] = '\n';
+	return len;
+}
+static DEVICE_ATTR_RO(multi_max_intensity);
+
 static ssize_t multi_intensity_store(struct device *dev,
 				struct device_attribute *intensity_attr,
 				const char *buf, size_t size)
@@ -35,6 +74,7 @@ static ssize_t multi_intensity_store(struct device *dev,
 	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
 	int nrchars, offset = 0;
 	unsigned int intensity_value[LED_COLOR_ID_MAX];
+	unsigned int max_intensity;
 	int i;
 	ssize_t ret;
 
@@ -56,8 +96,10 @@ static ssize_t multi_intensity_store(struct device *dev,
 		goto err_out;
 	}
 
-	for (i = 0; i < mcled_cdev->num_colors; i++)
-		mcled_cdev->subled_info[i].intensity = intensity_value[i];
+	for (i = 0; i < mcled_cdev->num_colors; i++) {
+		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
+		mcled_cdev->subled_info[i].intensity = min(intensity_value[i], max_intensity);
+	}
 
 	if (!test_bit(LED_BLINK_SW, &led_cdev->work_flags))
 		led_set_brightness(led_cdev, led_cdev->brightness);
@@ -111,6 +153,7 @@ static ssize_t multi_index_show(struct device *dev,
 static DEVICE_ATTR_RO(multi_index);
 
 static struct attribute *led_multicolor_attrs[] = {
+	&dev_attr_multi_max_intensity.attr,
 	&dev_attr_multi_intensity.attr,
 	&dev_attr_multi_index.attr,
 	NULL,
diff --git a/drivers/leds/leds-lp50xx.c b/drivers/leds/leds-lp50xx.c
index e2a9c8592953..69c3550f1a31 100644
--- a/drivers/leds/leds-lp50xx.c
+++ b/drivers/leds/leds-lp50xx.c
@@ -525,6 +525,7 @@ static int lp50xx_probe_dt(struct lp50xx *priv)
 			}
 
 			mc_led_info[multi_index].color_index = color_id;
+			mc_led_info[multi_index].max_intensity = 255;
 			num_colors++;
 		}
 
diff --git a/drivers/leds/rgb/leds-ncp5623.c b/drivers/leds/rgb/leds-ncp5623.c
index 85d6be6fff2b..f2528f06507d 100644
--- a/drivers/leds/rgb/leds-ncp5623.c
+++ b/drivers/leds/rgb/leds-ncp5623.c
@@ -56,8 +56,7 @@ static int ncp5623_brightness_set(struct led_classdev *cdev,
 	for (int i = 0; i < mc_cdev->num_colors; i++) {
 		ret = ncp5623_write(ncp->client,
 				    NCP5623_PWM_REG(mc_cdev->subled_info[i].channel),
-				    min(mc_cdev->subled_info[i].intensity,
-					NCP5623_MAX_BRIGHTNESS));
+				    mc_cdev->subled_info[i].intensity);
 		if (ret)
 			return ret;
 	}
@@ -190,6 +189,7 @@ static int ncp5623_probe(struct i2c_client *client)
 			goto release_led_node;
 
 		subled_info[ncp->mc_dev.num_colors].channel = reg;
+		subled_info[ncp->mc_dev.num_colors].max_intensity = NCP5623_MAX_BRIGHTNESS;
 		subled_info[ncp->mc_dev.num_colors++].color_index = color_index;
 	}
 
diff --git a/include/linux/led-class-multicolor.h b/include/linux/led-class-multicolor.h
index db9f34c6736e..26f6d20b887d 100644
--- a/include/linux/led-class-multicolor.h
+++ b/include/linux/led-class-multicolor.h
@@ -9,10 +9,31 @@
 #include <linux/leds.h>
 #include <dt-bindings/leds/common.h>
 
+/**
+ * struct mc_subled - Color component description.
+ * @color_index: Color ID.
+ * @brightness: Scaled intensity.
+ * @intensity: Current intensity.
+ * @max_intensity: Maximum supported intensity value.
+ * @channel: Channel index.
+ *
+ * Describes a color component of a multicolor LED. Many multicolor LEDs
+ * do no support gobal brightness control in hardware, so they use
+ * the brightness field in connection with led_mc_calc_color_components()
+ * to perform the intensity scaling in software.
+ * Such drivers should set max_intensity to 0 to signal the multicolor LED core
+ * that the maximum global brightness of the LED class device should be used for
+ * limiting incoming intensity values.
+ *
+ * Multicolor LEDs that do support global brightness control in hardware
+ * should instead set max_intensity to the maximum intensity value supported
+ * by the hardware for a given color component.
+ */
 struct mc_subled {
 	unsigned int color_index;
 	unsigned int brightness;
 	unsigned int intensity;
+	unsigned int max_intensity;
 	unsigned int channel;
 };
 
@@ -53,7 +74,14 @@ int led_classdev_multicolor_register_ext(struct device *parent,
  */
 void led_classdev_multicolor_unregister(struct led_classdev_mc *mcled_cdev);
 
-/* Calculate brightness for the monochrome LED cluster */
+/**
+ * led_mc_calc_color_components() - Calculates component brightness values of a LED cluster.
+ * @mcled_cdev - Multicolor LED class device of the LED cluster.
+ * @led_brightness - Global brightness of the LED cluster.
+ *
+ * Calculates the brightness values for each color component of a monochrome LED cluster,
+ * see Documentation/leds/leds-class-multicolor.rst for details.
+ */
 int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
 				 enum led_brightness brightness);
 
-- 
2.39.5

Re: [PATCH 1/1] leds: Introduce the multi_max_intensity sysfs attribute

[Werner Sembach]

Hi,

Am 24.03.26 um 21:27 schrieb Armin Wolf:
> Some multicolor LEDs support global brightness control in hardware,
> meaning that the maximum intensity of the color components is not
> connected to the maximum global brightness. Such LEDs cannot be
> described properly by the current multicolor LED class interface,
> because it assumes that the maximum intensity of each color component
> is described by the maximum global brightness of the LED.
>
> Fix this by introducing a new sysfs attribute called
> "multi_max_intensity" holding the maximum intensity values for the
> color components of a multicolor LED class device. Drivers can use
> the new max_intensity field inside struct mc_subled to tell the
> multicolor LED class code about those values. Intensity values written
> by userspace applications will be limited to this maximum value.
>
> Drivers for multicolor LEDs that do not support global brightness
> control in hardware might still want to use the maximum global LED
> brightness supplied via devicetree as the maximum intensity of each
> individual color component. Such drivers should set max_intensity
> to 0 so that the multicolor LED core can act accordingly.
>
> The lp50xx and ncp5623 LED drivers already use hardware-based control
> for the global LED brightness. Modify those drivers to correctly
> initalize .max_intensity to avoid being limited to the maximum global
> brightness supplied via devicetree.
>
> Signed-off-by: Armin Wolf <W_Armin@gmx.de>

lgtm

Reviewed-by: Werner Sembach <wse@tuxedocomputers.com>

Best regards,

Werner

> ---
>   .../ABI/testing/sysfs-class-led-multicolor    | 19 ++++++--
>   Documentation/leds/leds-class-multicolor.rst  | 21 ++++++++-
>   drivers/leds/led-class-multicolor.c           | 47 ++++++++++++++++++-
>   drivers/leds/leds-lp50xx.c                    |  1 +
>   drivers/leds/rgb/leds-ncp5623.c               |  4 +-
>   include/linux/led-class-multicolor.h          | 30 +++++++++++-
>   6 files changed, 113 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
> index 16fc827b10cb..197da3e775b4 100644
> --- a/Documentation/ABI/testing/sysfs-class-led-multicolor
> +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
> @@ -16,9 +16,22 @@ Date:		March 2020
>   KernelVersion:	5.9
>   Contact:	Dan Murphy <dmurphy@ti.com>
>   Description:	read/write
> -		This file contains array of integers. Order of components is
> -		described by the multi_index array. The maximum intensity should
> -		not exceed /sys/class/leds/<led>/max_brightness.
> +		This file contains an array of integers. The order of components
> +		is described by the multi_index array. The maximum intensity value
> +		supported by each color component is described by the multi_max_intensity
> +		file. Writing intensity values larger than the maximum value of a
> +		given color component will result in those values being clamped.
> +
> +		For additional details please refer to
> +		Documentation/leds/leds-class-multicolor.rst.
> +
> +What:		/sys/class/leds/<led>/multi_max_intensity
> +Date:		March 2026
> +KernelVersion:	7.1
> +Contact:	Armin Wolf <W_Armin@gmx.de>
> +Description:	read
> +		This file contains an array of integers describing the maximum
> +		intensity value for each intensity component.
>   
>   		For additional details please refer to
>   		Documentation/leds/leds-class-multicolor.rst.
> diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
> index c6b47b4093c4..8f42f10078ad 100644
> --- a/Documentation/leds/leds-class-multicolor.rst
> +++ b/Documentation/leds/leds-class-multicolor.rst
> @@ -25,10 +25,14 @@ color name to indexed value.
>   The ``multi_index`` file is an array that contains the string list of the colors as
>   they are defined in each ``multi_*`` array file.
>   
> -The ``multi_intensity`` is an array that can be read or written to for the
> +The ``multi_intensity`` file is an array that can be read or written to for the
>   individual color intensities.  All elements within this array must be written in
>   order for the color LED intensities to be updated.
>   
> +The ``multi_max_intensity`` file is an array that contains the maximum intensity
> +value supported by each color intensity. Intensity values above this will be
> +automatically clamped into the supported range.
> +
>   Directory Layout Example
>   ========================
>   .. code-block:: console
> @@ -38,6 +42,7 @@ Directory Layout Example
>       -r--r--r--    1 root     root          4096 Oct 19 16:16 max_brightness
>       -r--r--r--    1 root     root          4096 Oct 19 16:16 multi_index
>       -rw-r--r--    1 root     root          4096 Oct 19 16:16 multi_intensity
> +    -r--r--r--    1 root     root          4096 OCt 19 16:16 multi_max_intensity
>   
>   ..
>   
> @@ -104,3 +109,17 @@ the color LED group.
>       128
>   
>   ..
> +
> +Writing intensity values larger than the maximum specified in ``multi_max_intensity``
> +will result in those values being clamped into the supported range.
> +
> +.. code-block:: console
> +
> +   # cat /sys/class/leds/multicolor:status/multi_max_intensity
> +   255 255 255
> +
> +   # echo 512 512 512 > /sys/class/leds/multicolor:status/multi_intensity
> +   # cat /sys/class/leds/multicolor:status/multi_intensity
> +   255 255 255
> +
> +..
> diff --git a/drivers/leds/led-class-multicolor.c b/drivers/leds/led-class-multicolor.c
> index 6b671f3f9c61..13a35e6a28df 100644
> --- a/drivers/leds/led-class-multicolor.c
> +++ b/drivers/leds/led-class-multicolor.c
> @@ -7,10 +7,28 @@
>   #include <linux/init.h>
>   #include <linux/led-class-multicolor.h>
>   #include <linux/math.h>
> +#include <linux/minmax.h>
>   #include <linux/module.h>
>   #include <linux/slab.h>
>   #include <linux/uaccess.h>
>   
> +static unsigned int led_mc_get_max_intensity(struct led_classdev_mc *mcled_cdev, size_t index)
> +{
> +	unsigned int max_intensity;
> +
> +	/* The maximum global brightness value might still be changed by
> +	 * led_classdev_register_ext() using devicetree properties. This
> +	 * prevents us from changing subled_info[X].max_intensity when
> +	 * registering a multicolor LED class device, so we have to do
> +	 * this during runtime.
> +	 */
> +	max_intensity = mcled_cdev->subled_info[index].max_intensity;
> +	if (max_intensity)
> +		return max_intensity;
> +
> +	return mcled_cdev->led_cdev.max_brightness;
> +}
> +
>   int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>   				 enum led_brightness brightness)
>   {
> @@ -27,6 +45,27 @@ int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>   }
>   EXPORT_SYMBOL_GPL(led_mc_calc_color_components);
>   
> +static ssize_t multi_max_intensity_show(struct device *dev,
> +					struct device_attribute *intensity_attr, char *buf)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
> +	unsigned int max_intensity;
> +	int len = 0;
> +	int i;
> +
> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
> +		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
> +		len += sprintf(buf + len, "%u", max_intensity);
> +		if (i < mcled_cdev->num_colors - 1)
> +			len += sprintf(buf + len, " ");
> +	}
> +
> +	buf[len++] = '\n';
> +	return len;
> +}
> +static DEVICE_ATTR_RO(multi_max_intensity);
> +
>   static ssize_t multi_intensity_store(struct device *dev,
>   				struct device_attribute *intensity_attr,
>   				const char *buf, size_t size)
> @@ -35,6 +74,7 @@ static ssize_t multi_intensity_store(struct device *dev,
>   	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
>   	int nrchars, offset = 0;
>   	unsigned int intensity_value[LED_COLOR_ID_MAX];
> +	unsigned int max_intensity;
>   	int i;
>   	ssize_t ret;
>   
> @@ -56,8 +96,10 @@ static ssize_t multi_intensity_store(struct device *dev,
>   		goto err_out;
>   	}
>   
> -	for (i = 0; i < mcled_cdev->num_colors; i++)
> -		mcled_cdev->subled_info[i].intensity = intensity_value[i];
> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
> +		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
> +		mcled_cdev->subled_info[i].intensity = min(intensity_value[i], max_intensity);
> +	}
>   
>   	if (!test_bit(LED_BLINK_SW, &led_cdev->work_flags))
>   		led_set_brightness(led_cdev, led_cdev->brightness);
> @@ -111,6 +153,7 @@ static ssize_t multi_index_show(struct device *dev,
>   static DEVICE_ATTR_RO(multi_index);
>   
>   static struct attribute *led_multicolor_attrs[] = {
> +	&dev_attr_multi_max_intensity.attr,
>   	&dev_attr_multi_intensity.attr,
>   	&dev_attr_multi_index.attr,
>   	NULL,
> diff --git a/drivers/leds/leds-lp50xx.c b/drivers/leds/leds-lp50xx.c
> index e2a9c8592953..69c3550f1a31 100644
> --- a/drivers/leds/leds-lp50xx.c
> +++ b/drivers/leds/leds-lp50xx.c
> @@ -525,6 +525,7 @@ static int lp50xx_probe_dt(struct lp50xx *priv)
>   			}
>   
>   			mc_led_info[multi_index].color_index = color_id;
> +			mc_led_info[multi_index].max_intensity = 255;
>   			num_colors++;
>   		}
>   
> diff --git a/drivers/leds/rgb/leds-ncp5623.c b/drivers/leds/rgb/leds-ncp5623.c
> index 85d6be6fff2b..f2528f06507d 100644
> --- a/drivers/leds/rgb/leds-ncp5623.c
> +++ b/drivers/leds/rgb/leds-ncp5623.c
> @@ -56,8 +56,7 @@ static int ncp5623_brightness_set(struct led_classdev *cdev,
>   	for (int i = 0; i < mc_cdev->num_colors; i++) {
>   		ret = ncp5623_write(ncp->client,
>   				    NCP5623_PWM_REG(mc_cdev->subled_info[i].channel),
> -				    min(mc_cdev->subled_info[i].intensity,
> -					NCP5623_MAX_BRIGHTNESS));
> +				    mc_cdev->subled_info[i].intensity);
>   		if (ret)
>   			return ret;
>   	}
> @@ -190,6 +189,7 @@ static int ncp5623_probe(struct i2c_client *client)
>   			goto release_led_node;
>   
>   		subled_info[ncp->mc_dev.num_colors].channel = reg;
> +		subled_info[ncp->mc_dev.num_colors].max_intensity = NCP5623_MAX_BRIGHTNESS;
>   		subled_info[ncp->mc_dev.num_colors++].color_index = color_index;
>   	}
>   
> diff --git a/include/linux/led-class-multicolor.h b/include/linux/led-class-multicolor.h
> index db9f34c6736e..26f6d20b887d 100644
> --- a/include/linux/led-class-multicolor.h
> +++ b/include/linux/led-class-multicolor.h
> @@ -9,10 +9,31 @@
>   #include <linux/leds.h>
>   #include <dt-bindings/leds/common.h>
>   
> +/**
> + * struct mc_subled - Color component description.
> + * @color_index: Color ID.
> + * @brightness: Scaled intensity.
> + * @intensity: Current intensity.
> + * @max_intensity: Maximum supported intensity value.
> + * @channel: Channel index.
> + *
> + * Describes a color component of a multicolor LED. Many multicolor LEDs
> + * do no support gobal brightness control in hardware, so they use
> + * the brightness field in connection with led_mc_calc_color_components()
> + * to perform the intensity scaling in software.
> + * Such drivers should set max_intensity to 0 to signal the multicolor LED core
> + * that the maximum global brightness of the LED class device should be used for
> + * limiting incoming intensity values.
> + *
> + * Multicolor LEDs that do support global brightness control in hardware
> + * should instead set max_intensity to the maximum intensity value supported
> + * by the hardware for a given color component.
> + */
>   struct mc_subled {
>   	unsigned int color_index;
>   	unsigned int brightness;
>   	unsigned int intensity;
> +	unsigned int max_intensity;
>   	unsigned int channel;
>   };
>   
> @@ -53,7 +74,14 @@ int led_classdev_multicolor_register_ext(struct device *parent,
>    */
>   void led_classdev_multicolor_unregister(struct led_classdev_mc *mcled_cdev);
>   
> -/* Calculate brightness for the monochrome LED cluster */
> +/**
> + * led_mc_calc_color_components() - Calculates component brightness values of a LED cluster.
> + * @mcled_cdev - Multicolor LED class device of the LED cluster.
> + * @led_brightness - Global brightness of the LED cluster.
> + *
> + * Calculates the brightness values for each color component of a monochrome LED cluster,
> + * see Documentation/leds/leds-class-multicolor.rst for details.
> + */
>   int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>   				 enum led_brightness brightness);
>   

Re: [PATCH 1/1] leds: Introduce the multi_max_intensity sysfs attribute

[Jacek Anaszewski]

Hi Armin,

Thanks for the update.

On 3/24/26 9:27 PM, Armin Wolf wrote:
> Some multicolor LEDs support global brightness control in hardware,
> meaning that the maximum intensity of the color components is not
> connected to the maximum global brightness. Such LEDs cannot be
> described properly by the current multicolor LED class interface,
> because it assumes that the maximum intensity of each color component
> is described by the maximum global brightness of the LED.
> 
> Fix this by introducing a new sysfs attribute called
> "multi_max_intensity" holding the maximum intensity values for the
> color components of a multicolor LED class device. Drivers can use
> the new max_intensity field inside struct mc_subled to tell the
> multicolor LED class code about those values. Intensity values written
> by userspace applications will be limited to this maximum value.
> 
> Drivers for multicolor LEDs that do not support global brightness
> control in hardware might still want to use the maximum global LED
> brightness supplied via devicetree as the maximum intensity of each
> individual color component. Such drivers should set max_intensity
> to 0 so that the multicolor LED core can act accordingly.
> 
> The lp50xx and ncp5623 LED drivers already use hardware-based control
> for the global LED brightness. Modify those drivers to correctly
> initalize .max_intensity to avoid being limited to the maximum global
> brightness supplied via devicetree.
> 
> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
> ---
>   .../ABI/testing/sysfs-class-led-multicolor    | 19 ++++++--
>   Documentation/leds/leds-class-multicolor.rst  | 21 ++++++++-
>   drivers/leds/led-class-multicolor.c           | 47 ++++++++++++++++++-
>   drivers/leds/leds-lp50xx.c                    |  1 +
>   drivers/leds/rgb/leds-ncp5623.c               |  4 +-
>   include/linux/led-class-multicolor.h          | 30 +++++++++++-
>   6 files changed, 113 insertions(+), 9 deletions(-)
Reviewed-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

-- 
Best regards,
Jacek Anaszewski

Re: [PATCH 1/1] leds: Introduce the multi_max_intensity sysfs attribute

[Lee Jones]

On Tue, 24 Mar 2026, Armin Wolf wrote:

> Some multicolor LEDs support global brightness control in hardware,
> meaning that the maximum intensity of the color components is not
> connected to the maximum global brightness. Such LEDs cannot be
> described properly by the current multicolor LED class interface,
> because it assumes that the maximum intensity of each color component
> is described by the maximum global brightness of the LED.
> 
> Fix this by introducing a new sysfs attribute called
> "multi_max_intensity" holding the maximum intensity values for the
> color components of a multicolor LED class device. Drivers can use
> the new max_intensity field inside struct mc_subled to tell the
> multicolor LED class code about those values. Intensity values written
> by userspace applications will be limited to this maximum value.
> 
> Drivers for multicolor LEDs that do not support global brightness
> control in hardware might still want to use the maximum global LED
> brightness supplied via devicetree as the maximum intensity of each
> individual color component. Such drivers should set max_intensity
> to 0 so that the multicolor LED core can act accordingly.
> 
> The lp50xx and ncp5623 LED drivers already use hardware-based control
> for the global LED brightness. Modify those drivers to correctly
> initalize .max_intensity to avoid being limited to the maximum global
> brightness supplied via devicetree.
> 
> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
> ---
>  .../ABI/testing/sysfs-class-led-multicolor    | 19 ++++++--
>  Documentation/leds/leds-class-multicolor.rst  | 21 ++++++++-
>  drivers/leds/led-class-multicolor.c           | 47 ++++++++++++++++++-
>  drivers/leds/leds-lp50xx.c                    |  1 +
>  drivers/leds/rgb/leds-ncp5623.c               |  4 +-
>  include/linux/led-class-multicolor.h          | 30 +++++++++++-
>  6 files changed, 113 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
> index 16fc827b10cb..197da3e775b4 100644
> --- a/Documentation/ABI/testing/sysfs-class-led-multicolor
> +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
> @@ -16,9 +16,22 @@ Date:		March 2020
>  KernelVersion:	5.9
>  Contact:	Dan Murphy <dmurphy@ti.com>
>  Description:	read/write
> -		This file contains array of integers. Order of components is
> -		described by the multi_index array. The maximum intensity should
> -		not exceed /sys/class/leds/<led>/max_brightness.
> +		This file contains an array of integers. The order of components
> +		is described by the multi_index array. The maximum intensity value
> +		supported by each color component is described by the multi_max_intensity
> +		file. Writing intensity values larger than the maximum value of a
> +		given color component will result in those values being clamped.
> +
> +		For additional details please refer to
> +		Documentation/leds/leds-class-multicolor.rst.
> +
> +What:		/sys/class/leds/<led>/multi_max_intensity
> +Date:		March 2026
> +KernelVersion:	7.1
> +Contact:	Armin Wolf <W_Armin@gmx.de>
> +Description:	read
> +		This file contains an array of integers describing the maximum
> +		intensity value for each intensity component.
>  		For additional details please refer to
>  		Documentation/leds/leds-class-multicolor.rst.
> diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
> index c6b47b4093c4..8f42f10078ad 100644
> --- a/Documentation/leds/leds-class-multicolor.rst
> +++ b/Documentation/leds/leds-class-multicolor.rst
> @@ -25,10 +25,14 @@ color name to indexed value.
>  The ``multi_index`` file is an array that contains the string list of the colors as
>  they are defined in each ``multi_*`` array file.
>  
> -The ``multi_intensity`` is an array that can be read or written to for the
> +The ``multi_intensity`` file is an array that can be read or written to for the
>  individual color intensities.  All elements within this array must be written in
>  order for the color LED intensities to be updated.
>  
> +The ``multi_max_intensity`` file is an array that contains the maximum intensity
> +value supported by each color intensity. Intensity values above this will be
> +automatically clamped into the supported range.
> +
>  Directory Layout Example
>  ========================
>  .. code-block:: console
> @@ -38,6 +42,7 @@ Directory Layout Example
>      -r--r--r--    1 root     root          4096 Oct 19 16:16 max_brightness
>      -r--r--r--    1 root     root          4096 Oct 19 16:16 multi_index
>      -rw-r--r--    1 root     root          4096 Oct 19 16:16 multi_intensity
> +    -r--r--r--    1 root     root          4096 OCt 19 16:16 multi_max_intensity

Nit: Oct

>  
>  ..
>  
> @@ -104,3 +109,17 @@ the color LED group.
>      128
>  
>  ..
> +
> +Writing intensity values larger than the maximum specified in ``multi_max_intensity``
> +will result in those values being clamped into the supported range.
> +
> +.. code-block:: console
> +
> +   # cat /sys/class/leds/multicolor:status/multi_max_intensity
> +   255 255 255
> +
> +   # echo 512 512 512 > /sys/class/leds/multicolor:status/multi_intensity
> +   # cat /sys/class/leds/multicolor:status/multi_intensity
> +   255 255 255
> +
> +..
> diff --git a/drivers/leds/led-class-multicolor.c b/drivers/leds/led-class-multicolor.c
> index 6b671f3f9c61..13a35e6a28df 100644
> --- a/drivers/leds/led-class-multicolor.c
> +++ b/drivers/leds/led-class-multicolor.c
> @@ -7,10 +7,28 @@
>  #include <linux/init.h>
>  #include <linux/led-class-multicolor.h>
>  #include <linux/math.h>
> +#include <linux/minmax.h>
>  #include <linux/module.h>
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
>  
> +static unsigned int led_mc_get_max_intensity(struct led_classdev_mc *mcled_cdev, size_t index)
> +{
> +	unsigned int max_intensity;
> +
> +	/* The maximum global brightness value might still be changed by
> +	 * led_classdev_register_ext() using devicetree properties. This
> +	 * prevents us from changing subled_info[X].max_intensity when
> +	 * registering a multicolor LED class device, so we have to do
> +	 * this during runtime.
> +	 */
> +	max_intensity = mcled_cdev->subled_info[index].max_intensity;
> +	if (max_intensity)
> +		return max_intensity;
> +
> +	return mcled_cdev->led_cdev.max_brightness;
> +}
> +
>  int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>  				 enum led_brightness brightness)
>  {
> @@ -27,6 +45,27 @@ int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>  }
>  EXPORT_SYMBOL_GPL(led_mc_calc_color_components);
>  
> +static ssize_t multi_max_intensity_show(struct device *dev,
> +					struct device_attribute *intensity_attr, char *buf)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
> +	unsigned int max_intensity;
> +	int len = 0;
> +	int i;
> +
> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
> +		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
> +		len += sprintf(buf + len, "%u", max_intensity);
> +		if (i < mcled_cdev->num_colors - 1)
> +			len += sprintf(buf + len, " ");
> +	}

This should be 'sysfs_emit_at()'.

> +
> +	buf[len++] = '\n';
> +	return len;
> +}
> +static DEVICE_ATTR_RO(multi_max_intensity);
> +
>  static ssize_t multi_intensity_store(struct device *dev,
>  				struct device_attribute *intensity_attr,
>  				const char *buf, size_t size)
> @@ -35,6 +74,7 @@ static ssize_t multi_intensity_store(struct device *dev,
>  	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
>  	int nrchars, offset = 0;
>  	unsigned int intensity_value[LED_COLOR_ID_MAX];
> +	unsigned int max_intensity;
>  	int i;
>  	ssize_t ret;
>  
> @@ -56,8 +96,10 @@ static ssize_t multi_intensity_store(struct device *dev,
>  		goto err_out;
>  	}
>  
> -	for (i = 0; i < mcled_cdev->num_colors; i++)
> -		mcled_cdev->subled_info[i].intensity = intensity_value[i];
> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
> +		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
> +		mcled_cdev->subled_info[i].intensity = min(intensity_value[i], max_intensity);
> +	}
>  
>  	if (!test_bit(LED_BLINK_SW, &led_cdev->work_flags))
>  		led_set_brightness(led_cdev, led_cdev->brightness);
> @@ -111,6 +153,7 @@ static ssize_t multi_index_show(struct device *dev,
>  static DEVICE_ATTR_RO(multi_index);
>  
>  static struct attribute *led_multicolor_attrs[] = {
> +	&dev_attr_multi_max_intensity.attr,
>  	&dev_attr_multi_intensity.attr,
>  	&dev_attr_multi_index.attr,
>  	NULL,
> diff --git a/drivers/leds/leds-lp50xx.c b/drivers/leds/leds-lp50xx.c
> index e2a9c8592953..69c3550f1a31 100644
> --- a/drivers/leds/leds-lp50xx.c
> +++ b/drivers/leds/leds-lp50xx.c
> @@ -525,6 +525,7 @@ static int lp50xx_probe_dt(struct lp50xx *priv)
>  			}
>  
>  			mc_led_info[multi_index].color_index = color_id;
> +			mc_led_info[multi_index].max_intensity = 255;
>  			num_colors++;
>  		}
>  
> diff --git a/drivers/leds/rgb/leds-ncp5623.c b/drivers/leds/rgb/leds-ncp5623.c
> index 85d6be6fff2b..f2528f06507d 100644
> --- a/drivers/leds/rgb/leds-ncp5623.c
> +++ b/drivers/leds/rgb/leds-ncp5623.c
> @@ -56,8 +56,7 @@ static int ncp5623_brightness_set(struct led_classdev *cdev,
>  	for (int i = 0; i < mc_cdev->num_colors; i++) {
>  		ret = ncp5623_write(ncp->client,
>  				    NCP5623_PWM_REG(mc_cdev->subled_info[i].channel),
> -				    min(mc_cdev->subled_info[i].intensity,
> -					NCP5623_MAX_BRIGHTNESS));
> +				    mc_cdev->subled_info[i].intensity);
>  		if (ret)
>  			return ret;
>  	}
> @@ -190,6 +189,7 @@ static int ncp5623_probe(struct i2c_client *client)
>  			goto release_led_node;
>  
>  		subled_info[ncp->mc_dev.num_colors].channel = reg;
> +		subled_info[ncp->mc_dev.num_colors].max_intensity = NCP5623_MAX_BRIGHTNESS;
>  		subled_info[ncp->mc_dev.num_colors++].color_index = color_index;
>  	}
>  
> diff --git a/include/linux/led-class-multicolor.h b/include/linux/led-class-multicolor.h
> index db9f34c6736e..26f6d20b887d 100644
> --- a/include/linux/led-class-multicolor.h
> +++ b/include/linux/led-class-multicolor.h
> @@ -9,10 +9,31 @@
>  #include <linux/leds.h>
>  #include <dt-bindings/leds/common.h>
>  
> +/**
> + * struct mc_subled - Color component description.
> + * @color_index: Color ID.
> + * @brightness: Scaled intensity.
> + * @intensity: Current intensity.
> + * @max_intensity: Maximum supported intensity value.
> + * @channel: Channel index.
> + *
> + * Describes a color component of a multicolor LED. Many multicolor LEDs
> + * do no support gobal brightness control in hardware, so they use
> + * the brightness field in connection with led_mc_calc_color_components()
> + * to perform the intensity scaling in software.
> + * Such drivers should set max_intensity to 0 to signal the multicolor LED core
> + * that the maximum global brightness of the LED class device should be used for
> + * limiting incoming intensity values.
> + *
> + * Multicolor LEDs that do support global brightness control in hardware
> + * should instead set max_intensity to the maximum intensity value supported
> + * by the hardware for a given color component.
> + */
>  struct mc_subled {
>  	unsigned int color_index;
>  	unsigned int brightness;
>  	unsigned int intensity;
> +	unsigned int max_intensity;
>  	unsigned int channel;
>  };
>  
> @@ -53,7 +74,14 @@ int led_classdev_multicolor_register_ext(struct device *parent,
>   */
>  void led_classdev_multicolor_unregister(struct led_classdev_mc *mcled_cdev);
>  
> -/* Calculate brightness for the monochrome LED cluster */
> +/**
> + * led_mc_calc_color_components() - Calculates component brightness values of a LED cluster.
> + * @mcled_cdev - Multicolor LED class device of the LED cluster.
> + * @led_brightness - Global brightness of the LED cluster.

The header comment does not match the parameters.

Make sure you compile with W=1 to catch kernel-doc issues.

> + * Calculates the brightness values for each color component of a monochrome LED cluster,
> + * see Documentation/leds/leds-class-multicolor.rst for details.
> + */
>  int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>  				 enum led_brightness brightness);
>  
> -- 
> 2.39.5
> 
> 

-- 
Lee Jones [李琼斯]

Re: [PATCH 1/1] leds: Introduce the multi_max_intensity sysfs attribute

[Armin Wolf]

Am 31.03.26 um 12:38 schrieb Lee Jones:

> On Tue, 24 Mar 2026, Armin Wolf wrote:
>
>> Some multicolor LEDs support global brightness control in hardware,
>> meaning that the maximum intensity of the color components is not
>> connected to the maximum global brightness. Such LEDs cannot be
>> described properly by the current multicolor LED class interface,
>> because it assumes that the maximum intensity of each color component
>> is described by the maximum global brightness of the LED.
>>
>> Fix this by introducing a new sysfs attribute called
>> "multi_max_intensity" holding the maximum intensity values for the
>> color components of a multicolor LED class device. Drivers can use
>> the new max_intensity field inside struct mc_subled to tell the
>> multicolor LED class code about those values. Intensity values written
>> by userspace applications will be limited to this maximum value.
>>
>> Drivers for multicolor LEDs that do not support global brightness
>> control in hardware might still want to use the maximum global LED
>> brightness supplied via devicetree as the maximum intensity of each
>> individual color component. Such drivers should set max_intensity
>> to 0 so that the multicolor LED core can act accordingly.
>>
>> The lp50xx and ncp5623 LED drivers already use hardware-based control
>> for the global LED brightness. Modify those drivers to correctly
>> initalize .max_intensity to avoid being limited to the maximum global
>> brightness supplied via devicetree.
>>
>> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
>> ---
>>   .../ABI/testing/sysfs-class-led-multicolor    | 19 ++++++--
>>   Documentation/leds/leds-class-multicolor.rst  | 21 ++++++++-
>>   drivers/leds/led-class-multicolor.c           | 47 ++++++++++++++++++-
>>   drivers/leds/leds-lp50xx.c                    |  1 +
>>   drivers/leds/rgb/leds-ncp5623.c               |  4 +-
>>   include/linux/led-class-multicolor.h          | 30 +++++++++++-
>>   6 files changed, 113 insertions(+), 9 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
>> index 16fc827b10cb..197da3e775b4 100644
>> --- a/Documentation/ABI/testing/sysfs-class-led-multicolor
>> +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
>> @@ -16,9 +16,22 @@ Date:		March 2020
>>   KernelVersion:	5.9
>>   Contact:	Dan Murphy <dmurphy@ti.com>
>>   Description:	read/write
>> -		This file contains array of integers. Order of components is
>> -		described by the multi_index array. The maximum intensity should
>> -		not exceed /sys/class/leds/<led>/max_brightness.
>> +		This file contains an array of integers. The order of components
>> +		is described by the multi_index array. The maximum intensity value
>> +		supported by each color component is described by the multi_max_intensity
>> +		file. Writing intensity values larger than the maximum value of a
>> +		given color component will result in those values being clamped.
>> +
>> +		For additional details please refer to
>> +		Documentation/leds/leds-class-multicolor.rst.
>> +
>> +What:		/sys/class/leds/<led>/multi_max_intensity
>> +Date:		March 2026
>> +KernelVersion:	7.1
>> +Contact:	Armin Wolf <W_Armin@gmx.de>
>> +Description:	read
>> +		This file contains an array of integers describing the maximum
>> +		intensity value for each intensity component.
>>   		For additional details please refer to
>>   		Documentation/leds/leds-class-multicolor.rst.
>> diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
>> index c6b47b4093c4..8f42f10078ad 100644
>> --- a/Documentation/leds/leds-class-multicolor.rst
>> +++ b/Documentation/leds/leds-class-multicolor.rst
>> @@ -25,10 +25,14 @@ color name to indexed value.
>>   The ``multi_index`` file is an array that contains the string list of the colors as
>>   they are defined in each ``multi_*`` array file.
>>   
>> -The ``multi_intensity`` is an array that can be read or written to for the
>> +The ``multi_intensity`` file is an array that can be read or written to for the
>>   individual color intensities.  All elements within this array must be written in
>>   order for the color LED intensities to be updated.
>>   
>> +The ``multi_max_intensity`` file is an array that contains the maximum intensity
>> +value supported by each color intensity. Intensity values above this will be
>> +automatically clamped into the supported range.
>> +
>>   Directory Layout Example
>>   ========================
>>   .. code-block:: console
>> @@ -38,6 +42,7 @@ Directory Layout Example
>>       -r--r--r--    1 root     root          4096 Oct 19 16:16 max_brightness
>>       -r--r--r--    1 root     root          4096 Oct 19 16:16 multi_index
>>       -rw-r--r--    1 root     root          4096 Oct 19 16:16 multi_intensity
>> +    -r--r--r--    1 root     root          4096 OCt 19 16:16 multi_max_intensity
> Nit: Oct

Good catch, will fix.

>>   
>>   ..
>>   
>> @@ -104,3 +109,17 @@ the color LED group.
>>       128
>>   
>>   ..
>> +
>> +Writing intensity values larger than the maximum specified in ``multi_max_intensity``
>> +will result in those values being clamped into the supported range.
>> +
>> +.. code-block:: console
>> +
>> +   # cat /sys/class/leds/multicolor:status/multi_max_intensity
>> +   255 255 255
>> +
>> +   # echo 512 512 512 > /sys/class/leds/multicolor:status/multi_intensity
>> +   # cat /sys/class/leds/multicolor:status/multi_intensity
>> +   255 255 255
>> +
>> +..
>> diff --git a/drivers/leds/led-class-multicolor.c b/drivers/leds/led-class-multicolor.c
>> index 6b671f3f9c61..13a35e6a28df 100644
>> --- a/drivers/leds/led-class-multicolor.c
>> +++ b/drivers/leds/led-class-multicolor.c
>> @@ -7,10 +7,28 @@
>>   #include <linux/init.h>
>>   #include <linux/led-class-multicolor.h>
>>   #include <linux/math.h>
>> +#include <linux/minmax.h>
>>   #include <linux/module.h>
>>   #include <linux/slab.h>
>>   #include <linux/uaccess.h>
>>   
>> +static unsigned int led_mc_get_max_intensity(struct led_classdev_mc *mcled_cdev, size_t index)
>> +{
>> +	unsigned int max_intensity;
>> +
>> +	/* The maximum global brightness value might still be changed by
>> +	 * led_classdev_register_ext() using devicetree properties. This
>> +	 * prevents us from changing subled_info[X].max_intensity when
>> +	 * registering a multicolor LED class device, so we have to do
>> +	 * this during runtime.
>> +	 */
>> +	max_intensity = mcled_cdev->subled_info[index].max_intensity;
>> +	if (max_intensity)
>> +		return max_intensity;
>> +
>> +	return mcled_cdev->led_cdev.max_brightness;
>> +}
>> +
>>   int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>>   				 enum led_brightness brightness)
>>   {
>> @@ -27,6 +45,27 @@ int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>>   }
>>   EXPORT_SYMBOL_GPL(led_mc_calc_color_components);
>>   
>> +static ssize_t multi_max_intensity_show(struct device *dev,
>> +					struct device_attribute *intensity_attr, char *buf)
>> +{
>> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> +	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
>> +	unsigned int max_intensity;
>> +	int len = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
>> +		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
>> +		len += sprintf(buf + len, "%u", max_intensity);
>> +		if (i < mcled_cdev->num_colors - 1)
>> +			len += sprintf(buf + len, " ");
>> +	}
> This should be 'sysfs_emit_at()'.

Ok.

>> +
>> +	buf[len++] = '\n';
>> +	return len;
>> +}
>> +static DEVICE_ATTR_RO(multi_max_intensity);
>> +
>>   static ssize_t multi_intensity_store(struct device *dev,
>>   				struct device_attribute *intensity_attr,
>>   				const char *buf, size_t size)
>> @@ -35,6 +74,7 @@ static ssize_t multi_intensity_store(struct device *dev,
>>   	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
>>   	int nrchars, offset = 0;
>>   	unsigned int intensity_value[LED_COLOR_ID_MAX];
>> +	unsigned int max_intensity;
>>   	int i;
>>   	ssize_t ret;
>>   
>> @@ -56,8 +96,10 @@ static ssize_t multi_intensity_store(struct device *dev,
>>   		goto err_out;
>>   	}
>>   
>> -	for (i = 0; i < mcled_cdev->num_colors; i++)
>> -		mcled_cdev->subled_info[i].intensity = intensity_value[i];
>> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
>> +		max_intensity = led_mc_get_max_intensity(mcled_cdev, i);
>> +		mcled_cdev->subled_info[i].intensity = min(intensity_value[i], max_intensity);
>> +	}
>>   
>>   	if (!test_bit(LED_BLINK_SW, &led_cdev->work_flags))
>>   		led_set_brightness(led_cdev, led_cdev->brightness);
>> @@ -111,6 +153,7 @@ static ssize_t multi_index_show(struct device *dev,
>>   static DEVICE_ATTR_RO(multi_index);
>>   
>>   static struct attribute *led_multicolor_attrs[] = {
>> +	&dev_attr_multi_max_intensity.attr,
>>   	&dev_attr_multi_intensity.attr,
>>   	&dev_attr_multi_index.attr,
>>   	NULL,
>> diff --git a/drivers/leds/leds-lp50xx.c b/drivers/leds/leds-lp50xx.c
>> index e2a9c8592953..69c3550f1a31 100644
>> --- a/drivers/leds/leds-lp50xx.c
>> +++ b/drivers/leds/leds-lp50xx.c
>> @@ -525,6 +525,7 @@ static int lp50xx_probe_dt(struct lp50xx *priv)
>>   			}
>>   
>>   			mc_led_info[multi_index].color_index = color_id;
>> +			mc_led_info[multi_index].max_intensity = 255;
>>   			num_colors++;
>>   		}
>>   
>> diff --git a/drivers/leds/rgb/leds-ncp5623.c b/drivers/leds/rgb/leds-ncp5623.c
>> index 85d6be6fff2b..f2528f06507d 100644
>> --- a/drivers/leds/rgb/leds-ncp5623.c
>> +++ b/drivers/leds/rgb/leds-ncp5623.c
>> @@ -56,8 +56,7 @@ static int ncp5623_brightness_set(struct led_classdev *cdev,
>>   	for (int i = 0; i < mc_cdev->num_colors; i++) {
>>   		ret = ncp5623_write(ncp->client,
>>   				    NCP5623_PWM_REG(mc_cdev->subled_info[i].channel),
>> -				    min(mc_cdev->subled_info[i].intensity,
>> -					NCP5623_MAX_BRIGHTNESS));
>> +				    mc_cdev->subled_info[i].intensity);
>>   		if (ret)
>>   			return ret;
>>   	}
>> @@ -190,6 +189,7 @@ static int ncp5623_probe(struct i2c_client *client)
>>   			goto release_led_node;
>>   
>>   		subled_info[ncp->mc_dev.num_colors].channel = reg;
>> +		subled_info[ncp->mc_dev.num_colors].max_intensity = NCP5623_MAX_BRIGHTNESS;
>>   		subled_info[ncp->mc_dev.num_colors++].color_index = color_index;
>>   	}
>>   
>> diff --git a/include/linux/led-class-multicolor.h b/include/linux/led-class-multicolor.h
>> index db9f34c6736e..26f6d20b887d 100644
>> --- a/include/linux/led-class-multicolor.h
>> +++ b/include/linux/led-class-multicolor.h
>> @@ -9,10 +9,31 @@
>>   #include <linux/leds.h>
>>   #include <dt-bindings/leds/common.h>
>>   
>> +/**
>> + * struct mc_subled - Color component description.
>> + * @color_index: Color ID.
>> + * @brightness: Scaled intensity.
>> + * @intensity: Current intensity.
>> + * @max_intensity: Maximum supported intensity value.
>> + * @channel: Channel index.
>> + *
>> + * Describes a color component of a multicolor LED. Many multicolor LEDs
>> + * do no support gobal brightness control in hardware, so they use
>> + * the brightness field in connection with led_mc_calc_color_components()
>> + * to perform the intensity scaling in software.
>> + * Such drivers should set max_intensity to 0 to signal the multicolor LED core
>> + * that the maximum global brightness of the LED class device should be used for
>> + * limiting incoming intensity values.
>> + *
>> + * Multicolor LEDs that do support global brightness control in hardware
>> + * should instead set max_intensity to the maximum intensity value supported
>> + * by the hardware for a given color component.
>> + */
>>   struct mc_subled {
>>   	unsigned int color_index;
>>   	unsigned int brightness;
>>   	unsigned int intensity;
>> +	unsigned int max_intensity;
>>   	unsigned int channel;
>>   };
>>   
>> @@ -53,7 +74,14 @@ int led_classdev_multicolor_register_ext(struct device *parent,
>>    */
>>   void led_classdev_multicolor_unregister(struct led_classdev_mc *mcled_cdev);
>>   
>> -/* Calculate brightness for the monochrome LED cluster */
>> +/**
>> + * led_mc_calc_color_components() - Calculates component brightness values of a LED cluster.
>> + * @mcled_cdev - Multicolor LED class device of the LED cluster.
>> + * @led_brightness - Global brightness of the LED cluster.
> The header comment does not match the parameters.
>
> Make sure you compile with W=1 to catch kernel-doc issues.

Will do.

Thanks,
Armin Wolf

>> + * Calculates the brightness values for each color component of a monochrome LED cluster,
>> + * see Documentation/leds/leds-class-multicolor.rst for details.
>> + */
>>   int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
>>   				 enum led_brightness brightness);
>>   
>> -- 
>> 2.39.5
>>
>>