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Subject: Re: [PATCH v19 04/18] leds: multicolor: Introduce a multicolor class
 definition
To:     Dan Murphy <dmurphy@ti.com>, pavel@ucw.cz
Cc:     linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200402204311.14998-1-dmurphy@ti.com>
 <20200402204311.14998-5-dmurphy@ti.com>
From:   Jacek Anaszewski <jacek.anaszewski@gmail.com>
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Message-ID: <0beb0000-a8a3-4063-d165-fd804021342e@gmail.com>
Date:   Mon, 6 Apr 2020 21:25:41 +0200
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Hi Dan,

Thanks for the update. I have a few comments below.

On 4/2/20 10:42 PM, Dan Murphy wrote:
> Introduce a multicolor class that groups colored LEDs
> within a LED node.
> 
> The multi color class groups monochrome LEDs and allows controlling two
> aspects of the final combined color: hue and lightness. The former is
> controlled via <color>_intensity files and the latter is controlled
> via brightness file.
> 
> Signed-off-by: Dan Murphy <dmurphy@ti.com>
> ---
>  .../ABI/testing/sysfs-class-led-multicolor    |  42 ++++
>  Documentation/leds/index.rst                  |   1 +
>  Documentation/leds/leds-class-multicolor.rst  |  95 ++++++++
>  drivers/leds/Kconfig                          |  10 +
>  drivers/leds/Makefile                         |   1 +
>  drivers/leds/led-class-multicolor.c           | 206 ++++++++++++++++++
>  include/linux/led-class-multicolor.h          | 121 ++++++++++
>  7 files changed, 476 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-led-multicolor
>  create mode 100644 Documentation/leds/leds-class-multicolor.rst
>  create mode 100644 drivers/leds/led-class-multicolor.c
>  create mode 100644 include/linux/led-class-multicolor.h
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-led-multicolor b/Documentation/ABI/testing/sysfs-class-led-multicolor
> new file mode 100644
> index 000000000000..1f50324d24fd
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
> @@ -0,0 +1,42 @@
> +What:		/sys/class/leds/<led>/brightness
> +Date:		March 2020
> +KernelVersion:	5.8
> +Contact:	Dan Murphy <dmurphy@ti.com>
> +Description:	read/write
> +		Writing to this file will update all LEDs within the group to a
> +		calculated percentage of what each color LED intensity is set
> +		to. The percentage is calculated for each grouped LED via the
> +		equation below:
> +
> +		led_brightness = brightness * color_intensity/max_brightness
> +
> +		For additional details please refer to
> +		Documentation/leds/leds-class-multicolor.rst.
> +
> +		The value of the color is from 0 to
> +		/sys/class/leds/<led>/max_brightness.
> +
> +What:		/sys/class/leds/<led>/color_index
> +Date:		March 2020
> +KernelVersion:	5.8
> +Contact:	Dan Murphy <dmurphy@ti.com>
> +Description:	read
> +		The color_index array, when read, will output the LED colors
> +		by name as they are indexed in the color_intensity array.
> +
> +What:		/sys/class/leds/<led>/num_colors
> +Date:		March 2020
> +KernelVersion:	5.8
> +Contact:	Dan Murphy <dmurphy@ti.com>
> +Description:	read
> +		The num_colors indicates the number of LEDs defined in the
> +		color_intensity and color_index arrays.
> +
> +What:		/sys/class/leds/<led>/color_intensity
> +Date:		March 2020
> +KernelVersion:	5.8
> +Contact:	Dan Murphy <dmurphy@ti.com>
> +Description:	read/write
> +		Intensity level for the LED color within the array.
> +		The intensities for each color must be entered based on the
> +		color_index array.
> diff --git a/Documentation/leds/index.rst b/Documentation/leds/index.rst
> index 060f4e485897..bc70c6aa7138 100644
> --- a/Documentation/leds/index.rst
> +++ b/Documentation/leds/index.rst
> @@ -9,6 +9,7 @@ LEDs
>  
>     leds-class
>     leds-class-flash
> +   leds-class-multicolor
>     ledtrig-oneshot
>     ledtrig-transient
>     ledtrig-usbport
> diff --git a/Documentation/leds/leds-class-multicolor.rst b/Documentation/leds/leds-class-multicolor.rst
> new file mode 100644
> index 000000000000..5bb004999248
> --- /dev/null
> +++ b/Documentation/leds/leds-class-multicolor.rst
> @@ -0,0 +1,95 @@
> +====================================
> +Multi Color LED handling under Linux
> +====================================
> +
> +Description
> +===========
> +The multi color class groups monochrome LEDs and allows controlling two
> +aspects of the final combined color: hue and lightness. The former is
> +controlled via the color_intensity array file and the latter is controlled
> +via brightness file.
> +
> +For more details on hue and lightness notions please refer to
> +https://en.wikipedia.org/wiki/CIECAM02.
> +
> +Multicolor Class Control
> +========================
> +The multicolor class presents files that groups the colors as indexes in an
> +array.  These files are children under the LED parent node created by the
> +led_class framework.  The led_class framework is documented in led-class.rst
> +within this documentation directory.
> +
> +Each colored LED will be indexed under the color_* files. The order of the
> +colors are arbitrary the color_index file can be read to determine the color

Something wrong with punctuation here, or it is even a stylistic
problem.

> +to index value.
> +
> +The color_index file is an array that contains the string list of the colors as
> +they are defined in each color_* array file.
> +
> +The color_intensity 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 color_max_intensity is an array that can be read to indicate each color LED
> +maximum intensity value.
> +
> +The num_color_leds file returns the total number of color LEDs that are
> +presented in each color_* array.
> +
> +Directory Layout Example
> +========================
> +root:/sys/class/leds/multicolor:status# ls -lR
> +-rw-r--r--    1 root     root          4096 Oct 19 16:16 brightness
> +-r--r--r--    1 root     root          4096 Oct 19 16:16 color_index
> +-rw-r--r--    1 root     root          4096 Oct 19 16:16 color_intensity
> +-r--r--r--    1 root     root          4096 Oct 19 16:16 num_color_leds
> +
> +Multicolor Class Brightness Control
> +===================================
> +The multiclor class framework will calculate each monochrome LEDs intensity.
> +
> +The brightness level for each LED is calculated based on the color LED
> +intensity setting divided by the parent max_brightness setting multiplied by
> +the requested brightness.
> +
> +led_brightness = brightness * color_intensity/max_brightness
> +
> +Example:
> +A user first writes the color_intensity file with the brightness levels
> +that for each LED that is necessary to achieve a blueish violet output from a
> +RGB LED group.
> +
> +cat /sys/class/leds/multicolor:status/color_index
> +green blue red
> +
> +echo 43 226 138 > /sys/class/leds/multicolor:status/color_intensity
> +
> +red -
> +	intensity = 138
> +	max_brightness = 255
> +green -
> +	intensity = 43
> +	max_brightness = 255
> +blue -
> +	intensity = 226
> +	max_brightness = 255
> +
> +The user can control the brightness of that RGB group by writing the parent

s/RGB/multicolor/

> +'brightness' control.  Assuming a parent max_brightness of 255 the user may want
> +to dim the LED color group to half.  The user would write a value of 128 to the
> +parent brightness file then the values written to each LED will be adjusted
> +base on this value
> +
> +cat /sys/class/leds/multicolor:status/max_brightness
> +255
> +echo 128 > /sys/class/leds/multicolor:status/brightness
> +
> +adjusted_red_value = 128 * 138/255 = 69
> +adjusted_green_value = 128 * 43/255 = 21
> +adjusted_blue_value = 128 * 226/255 = 113
> +
> +Reading the parent brightness file will return the current brightness value of
> +the color LED group.
> +
> +cat /sys/class/leds/multicolor:status/brightness
> +128
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index d82f1dea3711..2e4611b25054 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -30,6 +30,16 @@ config LEDS_CLASS_FLASH
>  	  for the flash related features of a LED device. It can be built
>  	  as a module.
>  
> +config LEDS_CLASS_MULTI_COLOR
> +	tristate "LED Multi Color LED Class Support"
> +	depends on LEDS_CLASS
> +	help
> +	  This option enables the multicolor LED sysfs class in /sys/class/leds.
> +	  It wraps LED class and adds multicolor LED specific sysfs attributes
> +	  and kernel internal API to it. You'll need this to provide support
> +	  for multicolor LEDs that are grouped together. This class is not
> +	  intended for single color LEDs. It can be built as a module.
> +
>  config LEDS_BRIGHTNESS_HW_CHANGED
>  	bool "LED Class brightness_hw_changed attribute support"
>  	depends on LEDS_CLASS
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index d7e1107753fb..310b5518783a 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -4,6 +4,7 @@
>  obj-$(CONFIG_NEW_LEDS)			+= led-core.o
>  obj-$(CONFIG_LEDS_CLASS)		+= led-class.o
>  obj-$(CONFIG_LEDS_CLASS_FLASH)		+= led-class-flash.o
> +obj-$(CONFIG_LEDS_CLASS_MULTI_COLOR)	+= led-class-multicolor.o
>  obj-$(CONFIG_LEDS_TRIGGERS)		+= led-triggers.o
>  
>  # LED Platform Drivers
> diff --git a/drivers/leds/led-class-multicolor.c b/drivers/leds/led-class-multicolor.c
> new file mode 100644
> index 000000000000..838b1d679647
> --- /dev/null
> +++ b/drivers/leds/led-class-multicolor.c
> @@ -0,0 +1,206 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// LED Multi Color class interface
> +// Copyright (C) 2019-20 Texas Instruments Incorporated - http://www.ti.com/
> +// Author: Dan Murphy <dmurphy@ti.com>
> +
> +#include <linux/device.h>
> +#include <linux/init.h>
> +#include <linux/led-class-multicolor.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +#include "leds.h"
> +
> +int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
> +				 enum led_brightness brightness)
> +{
> +	struct led_classdev *led_cdev = &mcled_cdev->led_cdev;
> +	int i;
> +
> +	for (i = 0; i < mcled_cdev->num_colors; i++)
> +		mcled_cdev->multicolor_info[i].color_brightness = (brightness *
> +					  mcled_cdev->multicolor_info[i].color_led_intensity /
> +					  led_cdev->max_brightness);

Why the need for brackets?

> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(led_mc_calc_color_components);
> +
> +static ssize_t color_intensity_store(struct device *dev,
> +				struct device_attribute *intensity_attr,
> +				const char *buf, size_t size)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
> +	int nrchars, offset = 0;
> +	int intensity_value[LED_COLOR_ID_MAX];
> +	int i;
> +	ssize_t ret;
> +
> +	mutex_lock(&led_cdev->led_access);
> +
> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
> +		ret = sscanf(buf + offset, "%i%n",
> +			     &intensity_value[i], &nrchars);
> +		if (ret != 1) {
> +			dev_err(led_cdev->dev,
> +				"Incorrect number of LEDs expected %i values intensity was not applied\n",
> +				mcled_cdev->num_colors);
> +			goto err_out;
> +		}
> +		offset += nrchars;
> +	}
> +
> +	for (i = 0; i < mcled_cdev->num_colors; i++)
> +		mcled_cdev->multicolor_info[i].color_led_intensity =
> +					intensity_value[i];
> +
> +	led_set_brightness(led_cdev, led_cdev->brightness);
> +err_out:
> +	ret = size;
> +	mutex_unlock(&led_cdev->led_access);
> +	return ret;
> +}
> +
> +static ssize_t color_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);
> +	int len = 0;
> +	int i;
> +
> +	for (i = 0; i < mcled_cdev->num_colors; i++)
> +		len += sprintf(buf + len, "%d ",
> +			    mcled_cdev->multicolor_info[i].color_led_intensity);
> +
> +	len += sprintf(buf + len, "%s", "\n");
> +
> +	return len;
> +}
> +static DEVICE_ATTR_RW(color_intensity);
> +
> +static ssize_t color_index_show(struct device *dev,
> +			      struct device_attribute *color_index_attr,
> +			      char *buf)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
> +	int len = 0;
> +	int index;
> +	int i;
> +
> +	for (i = 0; i < mcled_cdev->num_colors; i++) {
> +		index = mcled_cdev->multicolor_info[i].color_index;
> +		len += sprintf(buf + len, "%s ", led_colors[index]);
> +	}
> +
> +	len += sprintf(buf + len, "%s", "\n");
> +
> +	return len;
> +}
> +static DEVICE_ATTR_RO(color_index);
> +
> +static ssize_t num_colors_show(struct device *dev,
> +				   struct device_attribute *max_intensity_attr,
> +				   char *buf)
> +{
> +	struct led_classdev *led_cdev = dev_get_drvdata(dev);
> +	struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
> +
> +	return sprintf(buf, "%d\n", mcled_cdev->num_colors);
> +}
> +static DEVICE_ATTR_RO(num_colors);
> +
> +static struct attribute *led_multicolor_attrs[] = {
> +	&dev_attr_color_intensity.attr,
> +	&dev_attr_color_index.attr,
> +	&dev_attr_num_colors.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(led_multicolor);
> +
> +int led_classdev_multicolor_register_ext(struct device *parent,
> +				     struct led_classdev_mc *mcled_cdev,
> +				     struct led_init_data *init_data)
> +{
> +	struct led_classdev *led_cdev;
> +
> +	if (!mcled_cdev)
> +		return -EINVAL;
> +
> +	if (!mcled_cdev->num_colors)
> +		return -EINVAL;
> +
> +	led_cdev = &mcled_cdev->led_cdev;
> +	mcled_cdev->led_cdev.groups = led_multicolor_groups;
> +
> +	return led_classdev_register_ext(parent, led_cdev, init_data);
> +}
> +EXPORT_SYMBOL_GPL(led_classdev_multicolor_register_ext);
> +
> +void led_classdev_multicolor_unregister(struct led_classdev_mc *mcled_cdev)
> +{
> +	if (!mcled_cdev)
> +		return;
> +
> +	led_classdev_unregister(&mcled_cdev->led_cdev);
> +}
> +EXPORT_SYMBOL_GPL(led_classdev_multicolor_unregister);
> +
> +static void devm_led_classdev_multicolor_release(struct device *dev, void *res)
> +{
> +	led_classdev_multicolor_unregister(*(struct led_classdev_mc **)res);
> +}
> +
> +int devm_led_classdev_multicolor_register_ext(struct device *parent,
> +					     struct led_classdev_mc *mcled_cdev,
> +					     struct led_init_data *init_data)
> +{
> +	struct led_classdev_mc **dr;
> +	int ret;
> +
> +	dr = devres_alloc(devm_led_classdev_multicolor_release,
> +			  sizeof(*dr), GFP_KERNEL);
> +	if (!dr)
> +		return -ENOMEM;
> +
> +	ret = led_classdev_multicolor_register_ext(parent, mcled_cdev,
> +						   init_data);
> +	if (ret) {
> +		devres_free(dr);
> +		return ret;
> +	}
> +
> +	*dr = mcled_cdev;
> +	devres_add(parent, dr);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(devm_led_classdev_multicolor_register_ext);
> +
> +static int devm_led_classdev_multicolor_match(struct device *dev,
> +					      void *res, void *data)
> +{
> +	struct led_classdev_mc **p = res;
> +
> +	if (WARN_ON(!p || !*p))
> +		return 0;
> +
> +	return *p == data;
> +}
> +
> +void devm_led_classdev_multicolor_unregister(struct device *dev,
> +					     struct led_classdev_mc *mcled_cdev)
> +{
> +	WARN_ON(devres_release(dev,
> +			       devm_led_classdev_multicolor_release,
> +			       devm_led_classdev_multicolor_match, mcled_cdev));
> +}
> +EXPORT_SYMBOL_GPL(devm_led_classdev_multicolor_unregister);
> +
> +MODULE_AUTHOR("Dan Murphy <dmurphy@ti.com>");
> +MODULE_DESCRIPTION("Multi Color LED class interface");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/linux/led-class-multicolor.h b/include/linux/led-class-multicolor.h
> new file mode 100644
> index 000000000000..a6a3715c0d48
> --- /dev/null
> +++ b/include/linux/led-class-multicolor.h
> @@ -0,0 +1,121 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* LED Multicolor class interface
> + * Copyright (C) 2019-20 Texas Instruments Incorporated - http://www.ti.com/
> + */
> +
> +#ifndef __LINUX_MULTICOLOR_LEDS_H_INCLUDED
> +#define __LINUX_MULTICOLOR_LEDS_H_INCLUDED
> +
> +#include <linux/leds.h>
> +#include <dt-bindings/leds/common.h>
> +
> +struct led_multicolor_info {
> +	int color_index;
> +	int color_brightness;
> +	int color_led_intensity;
> +	int color_channel;
> +};
> +
> +struct led_classdev_mc {
> +	/* led class device */
> +	struct led_classdev led_cdev;
> +	int num_colors;
> +
> +	struct led_multicolor_info multicolor_info[LED_COLOR_ID_MAX];

I still have a problem with this fixed array that can grow for each
driver as new color identifiers are added to the LED core. Not
mentioning waste of memory due to unused colors. This is bad design.

> +};
> +
> +static inline struct led_classdev_mc *lcdev_to_mccdev(
> +						struct led_classdev *led_cdev)
> +{
> +	return container_of(led_cdev, struct led_classdev_mc, led_cdev);
> +}
> +
> +#if IS_ENABLED(CONFIG_LEDS_CLASS_MULTI_COLOR)
> +/**
> + * led_classdev_multicolor_register_ext - register a new object of led_classdev
> + *				      class with support for multicolor LEDs
> + * @parent: the multicolor LED to register
> + * @mcled_cdev: the led_classdev_mc structure for this device
> + * @init_data: the LED class Multi color device initialization data
> + *
> + * Returns: 0 on success or negative error value on failure
> + */
> +int led_classdev_multicolor_register_ext(struct device *parent,
> +					    struct led_classdev_mc *mcled_cdev,
> +					    struct led_init_data *init_data);
> +
> +static inline int led_classdev_multicolor_register(struct device *parent,
> +					    struct led_classdev_mc *mcled_cdev)
> +{
> +	return led_classdev_multicolor_register_ext(parent, mcled_cdev, NULL);
> +}
> +
> +/**
> + * led_classdev_multicolor_unregister - unregisters an object of led_classdev
> + *					class with support for multicolor LEDs
> + * @mcled_cdev: the multicolor LED to unregister
> + *
> + * Unregister a previously registered via led_classdev_multicolor_register
> + * object
> + */
> +void led_classdev_multicolor_unregister(struct led_classdev_mc *mcled_cdev);
> +
> +/* Calculate brightness for the monochrome LED cluster */
> +int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
> +				 enum led_brightness brightness);
> +
> +int devm_led_classdev_multicolor_register_ext(struct device *parent,
> +					  struct led_classdev_mc *mcled_cdev,
> +					  struct led_init_data *init_data);
> +
> +static inline int devm_led_classdev_multicolor_register(struct device *parent,
> +				     struct led_classdev_mc *mcled_cdev)
> +{
> +	return devm_led_classdev_multicolor_register_ext(parent, mcled_cdev,
> +							 NULL);
> +}
> +
> +void devm_led_classdev_multicolor_unregister(struct device *parent,
> +					    struct led_classdev_mc *mcled_cdev);
> +#else
> +
> +static inline  int led_classdev_multicolor_register_ext(struct device *parent,
> +					    struct led_classdev_mc *mcled_cdev,
> +					    struct led_init_data *init_data)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int led_classdev_multicolor_register(struct device *parent,
> +					    struct led_classdev_mc *mcled_cdev)
> +{
> +	return led_classdev_multicolor_register_ext(parent, mcled_cdev, NULL);
> +}
> +
> +static inline void led_classdev_multicolor_unregister(struct led_classdev_mc *mcled_cdev) {};
> +static inline int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
> +					       enum led_brightness brightness)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int devm_led_classdev_multicolor_register_ext(struct device *parent,
> +					  struct led_classdev_mc *mcled_cdev,
> +					  struct led_init_data *init_data)
> +{
> +	return -EINVAL;
> +}
> +
> +static inline int devm_led_classdev_multicolor_register(struct device *parent,
> +					     struct led_classdev_mc *mcled_cdev)
> +{
> +	return devm_led_classdev_multicolor_register_ext(parent, mcled_cdev,
> +							 NULL);
> +}
> +
> +static inline void devm_led_classdev_multicolor_unregister(struct device *parent,
> +					    struct led_classdev_mc *mcled_cdev)
> +{};
> +
> +#endif  /* IS_ENABLED(CONFIG_LEDS_CLASS_MULTI_COLOR) */
> +#endif	/* __LINUX_MULTICOLOR_LEDS_H_INCLUDED */
> 

-- 
Best regards,
Jacek Anaszewski