Message-ID: <9a707fe6-31c6-da9e-9372-51ca21bf3c88@ti.com>
Date:   Sat, 28 Mar 2020 16:31:23 -0500
From:   Dan Murphy <dmurphy@...com>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>, <pavel@....cz>
CC:     <linux-leds@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v18 4/4] leds: multicolor: Introduce a multicolor class
 definition

Jacek

Thanks for the review

On 3/28/20 9:03 AM, Jacek Anaszewski wrote:
> Hi Dan,
>
> Thanks for the update. The picture would be more complete if
> the patch set contained a client though.

I was going to send the ones I did but they are pretty dirty from a code 
stand point.

Besides I would expect the framework to change which then changes the 
driver code.

> Anyway, please find my review remarks below.
>
> On 3/24/20 7:14 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
> s/files/file/

Ack


>> via brightness file.
>>
>> CC: Greg KH <gregkh@...uxfoundation.org>
>> Signed-off-by: Dan Murphy <dmurphy@...com>
>> ---
>> A design alternative to having files that having multiple values written to a
>> single file is here:
>>
>> https://lore.kernel.org/patchwork/patch/1186194/
>>
>>   .../ABI/testing/sysfs-class-led-multicolor    |  51 ++++
>>   Documentation/leds/index.rst                  |   1 +
>>   Documentation/leds/leds-class-multicolor.rst  | 110 +++++++++
>>   drivers/leds/Kconfig                          |  10 +
>>   drivers/leds/Makefile                         |   1 +
>>   drivers/leds/led-class-multicolor.c           | 224 ++++++++++++++++++
>>   include/linux/led-class-multicolor.h          | 124 ++++++++++
>>   7 files changed, 521 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..a93772212c21
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
>> @@ -0,0 +1,51 @@
>> +What:		/sys/class/leds/<led>/brightness
>> +Date:		March 2020
>> +KernelVersion:	5.8
>> +Contact:	Dan Murphy <dmurphy@...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/<color>_max_intensity
> We now have a single color_intensity file, so this needs to be rephrased.
Ack
>> +
>> +		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@...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_color_leds
> I would go for just num_colors.
Ack
>> +Date:		March 2020
>> +KernelVersion:	5.8
>> +Contact:	Dan Murphy <dmurphy@...com>
>> +Description:	read
>> +		The num_color_leds indicates the number of LEDs defined in the
>> +		color_intensity, color_max_intensity and color_index arrays.
>> +
>> +What:		/sys/class/leds/<led>/color_max_intensity
>> +Date:		March 2020
>> +KernelVersion:	5.8
>> +Contact:	Dan Murphy <dmurphy@...com>
>> +Description:	read
>> +		Maximum intensity level for the LED color within the array.
>> +		The max intensities for each color must be entered based on the
>> +		color_index array.
> I wonder if we should mention here that each LED within a cluster should
> have the same maximum intensity for linear color lightness calculation
> via brightness file.

Does it really have to?


>> +
>> +What:		/sys/class/leds/<led>/color_intensity
>> +Date:		March 2020
>> +KernelVersion:	5.8
>> +Contact:	Dan Murphy <dmurphy@...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..902a281a44d4
>> --- /dev/null
>> +++ b/Documentation/leds/leds-class-multicolor.rst
>> @@ -0,0 +1,110 @@
>> +====================================
>> +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.
>> +
>> +Note that intensity file only caches the written values and the actual
> s/intensity/color_intensity/
Ack
>
>> +change of hardware state occurs upon writing brightness file. This
>> +allows for changing many factors of the perceived color in a virtually
>> +unnoticeable way for the human observer.
> It will have to be changed after we agree upon exact semantics and
> interface of color_intensity, as I raised an issue below.
OK
>> +
>> +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
>> +to index value.
> This paragraph seems to be a leftover from some older version of the
> patch set.
>
Ack. I thought I vetted the file for completeness.
>> +
>> +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:grouped_leds# 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 color_max_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 color LED max intensity setting multiplied by
>> +the requested brightness.
>> +
>> +led_brightness = brightness * color_intensity/color_max_intensity
> Maybe some pseudo code would allow for better understanding here:
>
> for color in color_intensity
>      led[color].brightness = brightness *
> 	led[color].intensity / led[color].max_intensity
I think this would be fine at least there is a documented equation. I 
don't think we need to document the code.
>> +
>> +It is important to note that for each LED within the cluster the
>> +color_max_intensity value should be the same. This will help maintain a
>> +consistent hue across brightness levels.
>> +
>> +Example:
>> +A user first writes the color LEDs intensity file with the brightness levels
> s/color LEDs intensity/color_intensity/
Ack
>
>> +that for each LED that is necessary to achieve a blueish violet output from a
>> +RGB LED group.
>> +
>> +cat /sys/class/leds/multicolor:grouped_leds/color_index
> We don't have "grouped_leds" LED function so let's better use
> something available, like e.g "status".
Ack.
>
>> +green blue red
>> +
>> +echo 43 226 138 > /sys/class/leds/multicolor:grouped_leds/color_intensity
>> +
>> +red -
>> +	intensity = 138
>> +	max_intensity = 255
>> +green -
>> +	intensity = 43
>> +	max_intensity = 255
>> +blue -
>> +	intensity = 226
>> +	max_intensity = 255
>> +
>> +The user can control the brightness of that RGB group by writing the parent
>> +'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:grouped_leds/max_brightness
>> +255
>> +echo 128 > /sys/class/leds/multicolor:grouped_leds/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:grouped_leds/max_brightness
>> +255
>> +
>> +echo 128 > /sys/class/leds/multicolor:grouped_leds/brightness
> It was already written once above, no need to repeat.
Copy paste issue
>> +
>> +cat /sys/class/leds/multicolor:grouped_leds/brightness
>> +128
>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>> index d82f1dea3711..37dcdb06a29b 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 Mulit 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..0dbafede6e58
>> --- /dev/null
>> +++ b/drivers/leds/led-class-multicolor.c
>> @@ -0,0 +1,224 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +// LED Multi Color class interface
>> +// Copyright (C) 2019 Texas Instruments Incorporated - http://www.ti.com/
> I think that you deserve mentioning yourself as an author too.
Meh.
>> +
>> +#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)
>> +{
>> +	int i;
>> +
>> +	for (i = 0; i < mcled_cdev->num_colors; i++)
>> +		mcled_cdev->color_brightness[i] = brightness *
>> +					  mcled_cdev->color_led_intensity[i] /
>> +					  mcled_cdev->color_led_max_intensity[i];
>> +
>> +	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 *priv = 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 < priv->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",
>> +				priv->num_colors);
>> +			goto err_out;
>> +		}
>> +		offset += nrchars;
>> +	}
> I've just realized that moving to single color_intensity file
> doesn't allow setting all colors together with new brightness
> atomically. In effect, we will need to pass brightness to this file too,
> if we want to avoid "interesting" latching via brightenss file.
>
> Then we would need to call led_set_brightness() from here as well.

Why?  This just caches the intensity of each colored LED.  Then the 
actual brightness is calculated only when the brightness file is updated.

This would be an automatic update of the LED and that is not the intent 
of the intensity file per the documentation.

The user should be able to set the colors x number of times before the 
LED group is actually updated with the brightness.

>> +
>> +	memcpy(&priv->color_led_intensity, intensity_value,
>> +	       sizeof(intensity_value));
>> +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 *priv = lcdev_to_mccdev(led_cdev);
>> +	int len = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < priv->num_colors; i++)
>> +		len += sprintf(buf + len, "%d ", priv->color_led_intensity[i]);
>> +
>> +	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 *priv = lcdev_to_mccdev(led_cdev);
>> +	int len = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < priv->num_colors; i++)
>> +		len += sprintf(buf + len, "%s ", priv->color_index[i]);
>> +
>> +	len += sprintf(buf + len, "%s", "\n");
>> +
>> +	return len;
>> +}
>> +static DEVICE_ATTR_RO(color_index);
>> +
>> +static ssize_t color_max_intensity_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 *priv = lcdev_to_mccdev(led_cdev);
>> +	int len = 0;
>> +	int i;
>> +
>> +	for (i = 0; i < priv->num_colors; i++)
>> +		len += sprintf(buf + len, "%d ",
>> +			       priv->color_led_max_intensity[i]);
>> +
>> +	len += sprintf(buf + len, "%s", "\n");
>> +
>> +	return len;
>> +}
>> +static DEVICE_ATTR_RO(color_max_intensity);
>> +
>> +static ssize_t num_color_leds_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 *priv = lcdev_to_mccdev(led_cdev);
>> +
>> +	return sprintf(buf, "%d\n", priv->num_colors);
>> +}
>> +static DEVICE_ATTR_RO(num_color_leds);
>> +
>> +static struct attribute *led_multicolor_attrs[] = {
>> +	&dev_attr_color_intensity.attr,
>> +	&dev_attr_color_index.attr,
>> +	&dev_attr_color_max_intensity.attr,
>> +	&dev_attr_num_color_leds.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;
>> +	int i;
>> +
>> +	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;
>> +
>> +	for (i = 0; i <= mcled_cdev->num_colors; i++)
>> +		if (!mcled_cdev->color_led_max_intensity[i])
>> +			mcled_cdev->color_led_max_intensity[i] = LED_FULL;
>> +
>> +	return led_classdev_register_ext(parent, &mcled_cdev->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@...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..bfbde2e98340
>> --- /dev/null
>> +++ b/include/linux/led-class-multicolor.h
>> @@ -0,0 +1,124 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/* LED Multicolor class interface
>> + * Copyright (C) 2019 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_classdev_mc {
>> +	/* led class device */
>> +	struct led_classdev led_cdev;
>> +
>> +	struct device_attribute color_max_intensity_attr;
>> +	struct device_attribute color_intensity_attr;
>> +	struct device_attribute color_index_attr;
> These are no longer needed as you define attrs statically.
Ack
>> +
>> +	int color_brightness[LED_COLOR_ID_MAX];
>> +
>> +	int color_led_intensity[LED_COLOR_ID_MAX];
>> +	int color_led_max_intensity[LED_COLOR_ID_MAX];
>> +	const char *color_index[LED_COLOR_ID_MAX];
> I think that we should get back to the available_colors bitmask
> and allow the framework to allocate arrays by itself.
> And yes, all the above should be pointers.
>
> Driver would only need to set led_mcdev->available_colors bits.

Nack to the available_colors.  I did this originally and the issue is 
that the driver sets the bits in available_colors and no matter what the 
order is in the DT file the indexing is always red green and blue per 
the LED_COLORS array.  The framework has no legitimate way to know the 
order in which the colors were added.

This posed an issue with the LP55xx code as the RGB was defined with 
different colors assigned to different channels.  Green was 0 blue was 2 
and red was 6.  So the driver would have to map the channels to the 
colors.  In forcing the device driver to set the color index it can then 
map the output channels itself.  The framework should not care what 
channel is for what color.  In either case the device driver will need 
to store the color index mapped to the channel output but having the 
index to color being a 1-1 mapping made the code much simpler for the 
device driver.

Basically it turned out to be a simple for loop that just stored both 
channel and color as opposed to having to re-map the colors to indexes.

So for the LP55xx I can get an index of green, blue red and that maps to 
the channels per the DT.  I don't think the framework should enforce a 
standard color index array ordering.

If we use the available_colors we don't even need the color_index and we 
can just pass the available_colors to the user space as a u32 and let 
the user space figure what colors are available. Which means the user 
space would assume the order per the LED_COLORS array.

Dan

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