[PATCH v8 0/6] Add a multicolor LED driver for groups of monochromatic LEDs

[PATCH v8 0/6] Add a multicolor LED driver for groups of monochromatic LEDs

[Jean-Jacques Hiblot]

Some HW design implement multicolor LEDs with several monochromatic LEDs.
Grouping the monochromatic LEDs allows to configure them in sync and use
the triggers.
The PWM multicolor LED driver implements such grouping but only for
PWM-based LEDs. As this feature is also desirable for the other types of
LEDs, this series implements it for any kind of LED device.

changes v7->v8:
 - consistently use "LEDs group multicolor" throughout the code.
 - rename some variables with more explicit names.
 - improve comments.
 - use the 100-characters per line limit.

changes v6->v7:
 - in led_mcg_probe() increment the counter at the end of the loop for
   clarity.

changes v5->v6:
 - restore sysfs access to the leds when the device is removed

changes v4->v5:
 - Use "depends on COMPILE_TEST || OF" in Kconfig to indicate that OF
   is a functional requirement, not just a requirement for the
   compilation.
 - in led_mcg_probe() check if devm_of_led_get_optional() returns an
   error before testing for the end of the list.
 - use sysfs_emit() instead of sprintf() in color_show().
 - some grammar fixes in the comments and the commit logs.

changes v2->v3, only minor changes:
 - rephrased the Kconfig descritpion
 - make the sysfs interface of underlying LEDs read-only only if the probe
   is successful.
 - sanitize the header files
 - removed the useless call to dev_set_drvdata()
 - use dev_fwnode() to get the fwnode to the device.

changes v1->v2:
 - Followed Rob Herrings's suggestion to make the dt binding much simpler.
 - Added a patch to store the color property of a LED in its class
   structure (struct led_classdev).


Jean-Jacques Hiblot (6):
  devres: provide devm_krealloc_array()
  leds: class: simplify the implementation of devm_of_led_get()
  leds: provide devm_of_led_get_optional()
  leds: class: store the color index in struct led_classdev
  dt-bindings: leds: Add binding for a multicolor group of LEDs
  leds: Add a multicolor LED driver to group monochromatic LEDs

 Documentation/ABI/testing/sysfs-class-led     |   9 +
 .../bindings/leds/leds-group-multicolor.yaml  |  64 +++++++
 drivers/leds/led-class.c                      |  65 +++++--
 drivers/leds/rgb/Kconfig                      |  13 ++
 drivers/leds/rgb/Makefile                     |   1 +
 drivers/leds/rgb/leds-group-multicolor.c      | 164 ++++++++++++++++++
 include/linux/device.h                        |  13 ++
 include/linux/leds.h                          |   3 +
 8 files changed, 318 insertions(+), 14 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/leds/leds-group-multicolor.yaml
 create mode 100644 drivers/leds/rgb/leds-group-multicolor.c

-- 
2.25.1

[PATCH v8 1/6] devres: provide devm_krealloc_array()

[Jean-Jacques Hiblot]

Implement the managed variant of krealloc_array().
This internally uses devm_krealloc() and as such is usable with all memory
allocated by devm_kmalloc() (or devres functions using it implicitly like
devm_kmemdup(), devm_kstrdup() etc.).

Managed realloc'ed chunks can be manually released with devm_kfree().

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 include/linux/device.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/include/linux/device.h b/include/linux/device.h
index 44e3acae7b36..a9624478ac24 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -223,6 +223,19 @@ static inline void *devm_kcalloc(struct device *dev,
 {
 	return devm_kmalloc_array(dev, n, size, flags | __GFP_ZERO);
 }
+static inline void *devm_krealloc_array(struct device *dev,
+					void *p,
+					size_t new_n,
+					size_t new_size,
+					gfp_t flags)
+{
+	size_t bytes;
+
+	if (unlikely(check_mul_overflow(new_n, new_size, &bytes)))
+		return NULL;
+
+	return devm_krealloc(dev, p, bytes, flags);
+}
 void devm_kfree(struct device *dev, const void *p);
 char *devm_kstrdup(struct device *dev, const char *s, gfp_t gfp) __malloc;
 const char *devm_kstrdup_const(struct device *dev, const char *s, gfp_t gfp);
-- 
2.25.1

[PATCH v8 2/6] leds: class: simplify the implementation of devm_of_led_get()

[Jean-Jacques Hiblot]

Use the devm_add_action_or_reset() helper.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/leds/led-class.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 6a8ea94834fa..2c0d979d0c8a 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -258,11 +258,9 @@ void led_put(struct led_classdev *led_cdev)
 }
 EXPORT_SYMBOL_GPL(led_put);
 
-static void devm_led_release(struct device *dev, void *res)
+static void devm_led_release(void *cdev)
 {
-	struct led_classdev **p = res;
-
-	led_put(*p);
+	led_put(cdev);
 }
 
 /**
@@ -280,7 +278,7 @@ struct led_classdev *__must_check devm_of_led_get(struct device *dev,
 						  int index)
 {
 	struct led_classdev *led;
-	struct led_classdev **dr;
+	int ret;
 
 	if (!dev)
 		return ERR_PTR(-EINVAL);
@@ -289,15 +287,9 @@ struct led_classdev *__must_check devm_of_led_get(struct device *dev,
 	if (IS_ERR(led))
 		return led;
 
-	dr = devres_alloc(devm_led_release, sizeof(struct led_classdev *),
-			  GFP_KERNEL);
-	if (!dr) {
-		led_put(led);
-		return ERR_PTR(-ENOMEM);
-	}
-
-	*dr = led;
-	devres_add(dev, dr);
+	ret = devm_add_action_or_reset(dev, devm_led_release, led);
+	if (ret)
+		return ERR_PTR(ret);
 
 	return led;
 }
-- 
2.25.1

[PATCH v8 3/6] leds: provide devm_of_led_get_optional()

[Jean-Jacques Hiblot]

This version of devm_of_led_get() doesn't fail if a LED is not found.
Instead it returns a NULL pointer.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/leds/led-class.c | 25 +++++++++++++++++++++++++
 include/linux/leds.h     |  2 ++
 2 files changed, 27 insertions(+)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 2c0d979d0c8a..9cddcd908bce 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -295,6 +295,31 @@ struct led_classdev *__must_check devm_of_led_get(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_of_led_get);
 
+/**
+ * devm_of_led_get_optional - Resource-managed request of an optional LED device
+ * @dev:	LED consumer
+ * @index:	index of the LED to obtain in the consumer
+ *
+ * The device node of the device is parsed to find the requested LED device.
+ * The LED device returned from this function is automatically released
+ * on driver detach.
+ *
+ * @return a pointer to a LED device, ERR_PTR(errno) on failure and NULL if the
+ * led was not found.
+ */
+struct led_classdev *__must_check devm_of_led_get_optional(struct device *dev,
+							int index)
+{
+	struct led_classdev *led;
+
+	led = devm_of_led_get(dev, index);
+	if (IS_ERR(led) && PTR_ERR(led) == -ENOENT)
+		return NULL;
+
+	return led;
+}
+EXPORT_SYMBOL_GPL(devm_of_led_get_optional);
+
 static int led_classdev_next_name(const char *init_name, char *name,
 				  size_t len)
 {
diff --git a/include/linux/leds.h b/include/linux/leds.h
index ba4861ec73d3..41df18f42d00 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -215,6 +215,8 @@ extern struct led_classdev *of_led_get(struct device_node *np, int index);
 extern void led_put(struct led_classdev *led_cdev);
 struct led_classdev *__must_check devm_of_led_get(struct device *dev,
 						  int index);
+struct led_classdev *__must_check devm_of_led_get_optional(struct device *dev,
+						  int index);
 
 /**
  * led_blink_set - set blinking with software fallback
-- 
2.25.1

[PATCH v8 4/6] leds: class: store the color index in struct led_classdev

[Jean-Jacques Hiblot]

This information might be useful for more than only deriving the led's
name. And since we have this information, we can expose it in the sysfs.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
---
 Documentation/ABI/testing/sysfs-class-led |  9 +++++++++
 drivers/leds/led-class.c                  | 20 ++++++++++++++++++++
 include/linux/leds.h                      |  1 +
 3 files changed, 30 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led
index 2e24ac3bd7ef..c6e53213b1e7 100644
--- a/Documentation/ABI/testing/sysfs-class-led
+++ b/Documentation/ABI/testing/sysfs-class-led
@@ -59,6 +59,15 @@ Description:
 		brightness. Reading this file when no hw brightness change
 		event has happened will return an ENODATA error.
 
+What:		/sys/class/leds/<led>/color
+Date:		March 2023
+KernelVersion:	6.3
+Description:
+		Color of the led.
+
+		This is a read-only file. Reading this file returns the color
+		of the led as a string (ex: "red", "green").
+
 What:		/sys/class/leds/<led>/trigger
 Date:		March 2006
 KernelVersion:	2.6.17
diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 9cddcd908bce..4432e85a5fc6 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -74,6 +74,18 @@ static ssize_t max_brightness_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(max_brightness);
 
+static ssize_t color_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	const char *color_text = "invalid";
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+
+	if (led_cdev->color < LED_COLOR_ID_MAX)
+		color_text = led_colors[led_cdev->color];
+	return sysfs_emit(buf, "%s\n", color_text);
+}
+static DEVICE_ATTR_RO(color);
+
 #ifdef CONFIG_LEDS_TRIGGERS
 static BIN_ATTR(trigger, 0644, led_trigger_read, led_trigger_write, 0);
 static struct bin_attribute *led_trigger_bin_attrs[] = {
@@ -88,6 +100,7 @@ static const struct attribute_group led_trigger_group = {
 static struct attribute *led_class_attrs[] = {
 	&dev_attr_brightness.attr,
 	&dev_attr_max_brightness.attr,
+	&dev_attr_color.attr,
 	NULL,
 };
 
@@ -375,6 +388,10 @@ int led_classdev_register_ext(struct device *parent,
 			if (fwnode_property_present(init_data->fwnode,
 						    "retain-state-shutdown"))
 				led_cdev->flags |= LED_RETAIN_AT_SHUTDOWN;
+
+			if (fwnode_property_present(init_data->fwnode, "color"))
+				fwnode_property_read_u32(init_data->fwnode, "color",
+							 &led_cdev->color);
 		}
 	} else {
 		proposed_name = led_cdev->name;
@@ -384,6 +401,9 @@ int led_classdev_register_ext(struct device *parent,
 	if (ret < 0)
 		return ret;
 
+	if (led_cdev->color >= LED_COLOR_ID_MAX)
+		dev_warn(parent, "LED %s color identifier out of range\n", final_name);
+
 	mutex_init(&led_cdev->led_access);
 	mutex_lock(&led_cdev->led_access);
 	led_cdev->dev = device_create_with_groups(leds_class, parent, 0,
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 41df18f42d00..9d38cb90331d 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -71,6 +71,7 @@ struct led_classdev {
 	const char		*name;
 	unsigned int brightness;
 	unsigned int max_brightness;
+	unsigned int color;
 	int			 flags;
 
 	/* Lower 16 bits reflect status */
-- 
2.25.1

[PATCH v8 5/6] dt-bindings: leds: Add binding for a multicolor group of LEDs

[Jean-Jacques Hiblot]

This allows to group multiple monochromatic LEDs into a multicolor
LED, e.g. RGB LEDs.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Reviewed-by: Rob Herring <robh@kernel.org>
---
 .../bindings/leds/leds-group-multicolor.yaml  | 64 +++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/leds-group-multicolor.yaml

diff --git a/Documentation/devicetree/bindings/leds/leds-group-multicolor.yaml b/Documentation/devicetree/bindings/leds/leds-group-multicolor.yaml
new file mode 100644
index 000000000000..8ed059a5a724
--- /dev/null
+++ b/Documentation/devicetree/bindings/leds/leds-group-multicolor.yaml
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/leds/leds-group-multicolor.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Multi-color LED built with monochromatic LEDs
+
+maintainers:
+  - Jean-Jacques Hiblot <jjhiblot@traphandler.com>
+
+description: |
+  This driver combines several monochromatic LEDs into one multi-color
+  LED using the multicolor LED class.
+
+properties:
+  compatible:
+    const: leds-group-multicolor
+
+  leds:
+    description:
+      An aray of monochromatic leds
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+
+required:
+  - leds
+
+allOf:
+  - $ref: leds-class-multicolor.yaml#
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/leds/common.h>
+
+    monochromatic-leds {
+        compatible = "gpio-leds";
+
+        led0: led-0 {
+            gpios = <&mcu_pio 0 GPIO_ACTIVE_LOW>;
+            color = <LED_COLOR_ID_RED>;
+        };
+
+        led1: led-1 {
+            gpios = <&mcu_pio 1 GPIO_ACTIVE_HIGH>;
+            color = <LED_COLOR_ID_GREEN>;
+        };
+
+        led2: led-2 {
+            gpios = <&mcu_pio 2 GPIO_ACTIVE_HIGH>;
+            color = <LED_COLOR_ID_BLUE>;
+        };
+    };
+
+    multi-led {
+        compatible = "leds-group-multicolor";
+        color = <LED_COLOR_ID_RGB>;
+        function = LED_FUNCTION_INDICATOR;
+        leds = <&led0>, <&led1>, <&led2>;
+    };
+
+...
-- 
2.25.1

[PATCH v8 6/6] leds: Add a multicolor LED driver to group monochromatic LEDs

[Jean-Jacques Hiblot]

Grouping multiple monochrome LEDs into a multicolor LED device has a few
benefits over handling the group in user-space:
- The state of the LEDs relative to each other is consistent. In other
  words, if 2 threads competes to set the LED to green and red, the
  end-result cannot be black or yellow.
- The multicolor LED as a whole can be driven through the sysfs LED
  interface.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
---
 drivers/leds/rgb/Kconfig                 |  13 ++
 drivers/leds/rgb/Makefile                |   1 +
 drivers/leds/rgb/leds-group-multicolor.c | 164 +++++++++++++++++++++++
 3 files changed, 178 insertions(+)
 create mode 100644 drivers/leds/rgb/leds-group-multicolor.c

diff --git a/drivers/leds/rgb/Kconfig b/drivers/leds/rgb/Kconfig
index 204cf470beae..1f85df5b691d 100644
--- a/drivers/leds/rgb/Kconfig
+++ b/drivers/leds/rgb/Kconfig
@@ -2,6 +2,19 @@
 
 if LEDS_CLASS_MULTICOLOR
 
+config LEDS_GROUP_MULTICOLOR
+	tristate "LEDs group multi-color support"
+	depends on OF || COMPILE_TEST
+	help
+	  This option enables support for monochrome LEDs that are
+	  grouped into multicolor LEDs.
+	  This useful in the case where LEDs of different colors are
+	  physically grouped in a single multi-color LED and driven
+	  by a controller that doesn't have multi-color support.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called leds-group-multicolor.
+
 config LEDS_PWM_MULTICOLOR
 	tristate "PWM driven multi-color LED Support"
 	depends on PWM
diff --git a/drivers/leds/rgb/Makefile b/drivers/leds/rgb/Makefile
index 0675bc0f6e18..64d0d7ad5341 100644
--- a/drivers/leds/rgb/Makefile
+++ b/drivers/leds/rgb/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 
+obj-$(CONFIG_LEDS_GROUP_MULTICOLOR)	+= leds-group-multicolor.o
 obj-$(CONFIG_LEDS_PWM_MULTICOLOR)	+= leds-pwm-multicolor.o
 obj-$(CONFIG_LEDS_QCOM_LPG)		+= leds-qcom-lpg.o
diff --git a/drivers/leds/rgb/leds-group-multicolor.c b/drivers/leds/rgb/leds-group-multicolor.c
new file mode 100644
index 000000000000..27c80c84de88
--- /dev/null
+++ b/drivers/leds/rgb/leds-group-multicolor.c
@@ -0,0 +1,164 @@
+// 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 the 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 led_mcg_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_access(void *data)
+{
+	struct led_classdev *led_cdev = data;
+
+	mutex_lock(&led_cdev->led_access);
+	led_sysfs_enable(led_cdev);
+	mutex_unlock(&led_cdev->led_access);
+}
+
+static int led_mcg_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 = led_mcg_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 = led_mcg_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 sysfs of the monochromatic LED read-only */
+		mutex_lock(&led_cdev->led_access);
+		led_sysfs_disable(led_cdev);
+		mutex_unlock(&led_cdev->led_access);
+
+		/* Restore sysfs access when the multicolor LED is released */
+		devm_add_action_or_reset(dev, restore_sysfs_access, led_cdev);
+	}
+
+	return 0;
+}
+
+static const struct of_device_id of_led_group_multicolor_match[] = {
+	{ .compatible = "leds-group-multicolor" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, of_led_group_multicolor_match);
+
+static struct platform_driver led_group_multicolor_driver = {
+	.probe		= led_mcg_probe,
+	.driver		= {
+		.name	= "leds_group_multicolor",
+		.of_match_table = of_led_group_multicolor_match,
+	}
+};
+module_platform_driver(led_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");
-- 
2.25.1

Re: [PATCH v8 4/6] leds: class: store the color index in struct led_classdev

[Andy Shevchenko]

On Tue, Mar 28, 2023 at 7:15 PM Jean-Jacques Hiblot
<jjhiblot@traphandler.com> wrote:
>
> This information might be useful for more than only deriving the led's
> name. And since we have this information, we can expose it in the sysfs.

...

> +Date:          March 2023
> +KernelVersion: 6.3

Outdated version.

...

> +               Color of the led.
> +
> +               This is a read-only file. Reading this file returns the color
> +               of the led as a string (ex: "red", "green").

There are no strict rules about colour and I don't think it's a good
idea. Why in such a case is it different to label? My proposal here at
least documenting that the colour must follow one of the existing
naming standards (like RGB in hex, HTML, or name in accordance with
chosen standard).

Yet, it won't technically prevent abusing that, but at least will show
the intention and allow pointing out to the bugs or develop user space
tooling based on existing parsers (if any).

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v8 6/6] leds: Add a multicolor LED driver to group monochromatic LEDs

[Andy Shevchenko]

On Tue, Mar 28, 2023 at 7:15 PM Jean-Jacques Hiblot
<jjhiblot@traphandler.com> wrote:
>
> Grouping multiple monochrome LEDs into a multicolor LED device has a few
> benefits over handling the group in user-space:
> - The state of the LEDs relative to each other is consistent. In other
>   words, if 2 threads competes to set the LED to green and red, the
>   end-result cannot be black or yellow.
> - The multicolor LED as a whole can be driven through the sysfs LED
>   interface.

...

> +config LEDS_GROUP_MULTICOLOR
> +       tristate "LEDs group multi-color support"
> +       depends on OF || COMPILE_TEST

Why is OF a dependency?
Can't we make it a firmware provider agnostic solution from day 1?

> +       help
> +         This option enables support for monochrome LEDs that are
> +         grouped into multicolor LEDs.
> +         This useful in the case where LEDs of different colors are

This is

> +         physically grouped in a single multi-color LED and driven
> +         by a controller that doesn't have multi-color support.
> +
> +         To compile this driver as a module, choose M here: the module
> +         will be called leds-group-multicolor.

...

> +               led_cdev = devm_of_led_get_optional(dev, count);

I don't see how this is OF specific to this driver. Maybe it needs to
be patched first, so we will have something non-OF specific?

> +               if (IS_ERR(led_cdev))
> +                       return dev_err_probe(dev, PTR_ERR(led_cdev), "Unable to get LED #%d",
> +                                            count);

At least we need to have a FIXME or so here.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v8 4/6] leds: class: store the color index in struct led_classdev

[Jean-Jacques Hiblot]

On 28/03/2023 19:15, Andy Shevchenko wrote:
> On Tue, Mar 28, 2023 at 7:15 PM Jean-Jacques Hiblot
> <jjhiblot@traphandler.com> wrote:
>>
>> This information might be useful for more than only deriving the led's
>> name. And since we have this information, we can expose it in the sysfs.
> 
> ...
> 
>> +Date:          March 2023
>> +KernelVersion: 6.3
> 
> Outdated version.
> 
> ...
> 
>> +               Color of the led.
>> +
>> +               This is a read-only file. Reading this file returns the color
>> +               of the led as a string (ex: "red", "green").
> 
> There are no strict rules about colour and I don't think it's a good
> idea. Why in such a case is it different to label? My proposal here at
> least documenting that the colour must follow one of the existing
> naming standards (like RGB in hex, HTML, or name in accordance with
> chosen standard).
Actually the colors are defined in an array: led_colors (led-core.c: 88)
So the color is one of the following: white, red, reen, blue, amber, 
violet, yellow, ir, multicolor, rgb

There is mention in the TODO file of changing the way RGB leds are 
handled and the RGB leds would probably show the hex RGB values here.

> 
> Yet, it won't technically prevent abusing that, but at least will show
> the intention and allow pointing out to the bugs or develop user space
> tooling based on existing parsers (if any).
> 

Re: [PATCH v8 6/6] leds: Add a multicolor LED driver to group monochromatic LEDs

[Jean-Jacques Hiblot]

On 28/03/2023 19:20, Andy Shevchenko wrote:
> On Tue, Mar 28, 2023 at 7:15 PM Jean-Jacques Hiblot
> <jjhiblot@traphandler.com> wrote:
>>
>> Grouping multiple monochrome LEDs into a multicolor LED device has a few
>> benefits over handling the group in user-space:
>> - The state of the LEDs relative to each other is consistent. In other
>>    words, if 2 threads competes to set the LED to green and red, the
>>    end-result cannot be black or yellow.
>> - The multicolor LED as a whole can be driven through the sysfs LED
>>    interface.
> 
> ...
> 
>> +config LEDS_GROUP_MULTICOLOR
>> +       tristate "LEDs group multi-color support"
>> +       depends on OF || COMPILE_TEST
> 
> Why is OF a dependency?
> Can't we make it a firmware provider agnostic solution from day 1?
That would be possible, unfortunately I have no way of testing the ACPI 
stuff. That's why I prefer sticking to OF.

> 
>> +       help
>> +         This option enables support for monochrome LEDs that are
>> +         grouped into multicolor LEDs.
>> +         This useful in the case where LEDs of different colors are
> 
> This is
> 
>> +         physically grouped in a single multi-color LED and driven
>> +         by a controller that doesn't have multi-color support.
>> +
>> +         To compile this driver as a module, choose M here: the module
>> +         will be called leds-group-multicolor.
> 
> ...
> 
>> +               led_cdev = devm_of_led_get_optional(dev, count);
> 
> I don't see how this is OF specific to this driver. Maybe it needs to
> be patched first, so we will have something non-OF specific?
> 
>> +               if (IS_ERR(led_cdev))
>> +                       return dev_err_probe(dev, PTR_ERR(led_cdev), "Unable to get LED #%d",
>> +                                            count);
> 
> At least we need to have a FIXME or so here.
>