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Subject: Re: [PATCH v15 04/19] 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: <20191028183629.11779-1-dmurphy@ti.com>
 <20191028183629.11779-5-dmurphy@ti.com>
From:   Jacek Anaszewski <jacek.anaszewski@gmail.com>
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Message-ID: <6dbd4e43-4832-4f8e-4eb9-8b7c878c270e@gmail.com>
Date:   Mon, 28 Oct 2019 20:22:39 +0100
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Dan,

Thank you for the v15.

On 10/28/19 7:36 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    |  36 +++
>  Documentation/leds/index.rst                  |   1 +
>  Documentation/leds/leds-class-multicolor.rst  | 100 +++++++
>  drivers/leds/Kconfig                          |  10 +
>  drivers/leds/Makefile                         |   1 +
>  drivers/leds/led-class-multicolor.c           | 271 ++++++++++++++++++
>  include/linux/led-class-multicolor.h          | 139 +++++++++
>  7 files changed, 558 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..3d1f9d726c70
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-led-multicolor
> @@ -0,0 +1,36 @@
> +What:		/sys/class/leds/<led>/brightness
> +Date:		Sept 2019
> +KernelVersion:	5.5
> +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/<color>_max_intensity
> +
> +		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>/colors/<color>_intensity
> +Date:		Sept 2019
> +KernelVersion:	5.5
> +Contact:	Dan Murphy <dmurphy@ti.com>
> +Description:	read/write
> +		The <color>_intensity file is created based on the color
> +		defined by the registrar of the class.
> +		There is one file per color presented.
> +
> +		The value of the color is from 0 to
> +		/sys/class/leds/<led>/colors/<color>_max_intensity.
> +
> +What:		/sys/class/leds/<led>/colors/<color>_max_intensity
> +Date:		Sept 2019
> +KernelVersion:	5.5
> +Contact:	Dan Murphy <dmurphy@ti.com>
> +Description:	read only
> +		Maximum intensity level for the LED color.
> 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..c8a224cead51
> --- /dev/null
> +++ b/Documentation/leds/leds-class-multicolor.rst
> @@ -0,0 +1,100 @@
> +====================================
> +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 <color>_intensity files 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 files only cache the written value and the actual
> +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.
> +
> +Multicolor Class Control
> +========================
> +The multicolor class presents the LED groups under a directory called "colors".
> +This directory is a child 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 have two files created under the colors directory
> +<color>_intensity and <color>_max_intensity. These files will contain
> +one of LED_COLOR_ID_* definitions from the header
> +include/dt-bindings/leds/common.h.
> +
> +Directory Layout Example
> +========================
> +root:/sys/class/leds/rgb:grouped_leds# ls -lR colors/

s/rgb/multicolor/ according to the led_colors[LED_COLOR_ID_MULTI].

> +-rw-r--r--    1 root     root          4096 Jul  7 03:10 blue_intensity
> +-r--r--r--    1 root     root          4096 Jul  7 03:10 blue_max_intensity
> +-rw-r--r--    1 root     root          4096 Jul  7 03:10 green_intensity
> +-r--r--r--    1 root     root          4096 Jul  7 03:10 green_max_intensity
> +-rw-r--r--    1 root     root          4096 Jul  7 03:10 red_intensity
> +-r--r--r--    1 root     root          4096 Jul  7 03:10 red_max_intensity
> +
[...]
> +static int led_multicolor_init_color(struct led_classdev_mc *mcled_cdev,
> +				     int color_id)
> +{
> +	struct led_classdev *led_cdev = mcled_cdev->led_cdev;
> +	struct led_mc_color_entry *mc_priv;
> +	char *intensity_file_name;
> +	char *max_intensity_file_name;
> +	size_t len;
> +	int ret;
> +
> +	mc_priv = devm_kzalloc(led_cdev->dev, sizeof(*mc_priv), GFP_KERNEL);
> +	if (!mc_priv)
> +		return -ENOMEM;
> +
> +	mc_priv->led_color_id = color_id;
> +	mc_priv->mcled_cdev = mcled_cdev;
> +
> +	sysfs_attr_init(&mc_priv->intensity_attr.attr);
> +	len = strlen(led_colors[color_id]) + strlen(INTENSITY_NAME) + 1;
> +	intensity_file_name = kzalloc(len, GFP_KERNEL);
> +	if (!intensity_file_name)
> +		return -ENOMEM;
> +
> +	snprintf(intensity_file_name, len, "%s%s",
> +		 led_colors[color_id], INTENSITY_NAME);
> +	mc_priv->intensity_attr.attr.name = intensity_file_name;
> +	mc_priv->intensity_attr.attr.mode = 0644;
> +	mc_priv->intensity_attr.store = intensity_store;
> +	mc_priv->intensity_attr.show = intensity_show;
> +	ret = sysfs_add_file_to_group(&led_cdev->dev->kobj,
> +				      &mc_priv->intensity_attr.attr,
> +				      led_color_group.name);
> +	if (ret)
> +		goto intensity_err_out;
> +
> +	sysfs_attr_init(&mc_priv->max_intensity_attr.attr);
> +	len = strlen(led_colors[color_id]) + strlen(MAX_INTENSITY_NAME) + 1;
> +	max_intensity_file_name = kzalloc(len, GFP_KERNEL);
> +	if (!max_intensity_file_name) {
> +		ret = -ENOMEM;
> +		goto intensity_err_out;
> +	}
> +
> +	snprintf(max_intensity_file_name, len, "%s%s",
> +		 led_colors[color_id], MAX_INTENSITY_NAME);
> +	mc_priv->max_intensity_attr.attr.name = max_intensity_file_name;
> +	mc_priv->max_intensity_attr.attr.mode = 0444;
> +	mc_priv->max_intensity_attr.show = max_intensity_show;
> +	ret = sysfs_add_file_to_group(&led_cdev->dev->kobj,
> +				      &mc_priv->max_intensity_attr.attr,
> +				      led_color_group.name);
> +	if (ret)
> +		goto max_intensity_err_out;
> +
> +	mc_priv->max_intensity = LED_FULL;
> +	list_add_tail(&mc_priv->list, &mcled_cdev->color_list);

I still would prefer dynamically allocated array here. Also there are
things I would see differently in the patch 13/19 as already discussed.

Nonetheless I am giving my preliminary ack for this series just to
give a hint to others to join the review.

-- 
Best regards,
Jacek Anaszewski