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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>
 <6dbd4e43-4832-4f8e-4eb9-8b7c878c270e@gmail.com>
 <5e4ff68d-bb53-d3cd-f1b7-68c418342657@ti.com>
From:   Jacek Anaszewski <jacek.anaszewski@gmail.com>
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Message-ID: <df5d8868-d332-6320-b065-29b596fdc855@gmail.com>
Date:   Mon, 28 Oct 2019 21:04:55 +0100
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Dan,

On 10/28/19 8:36 PM, Dan Murphy wrote:
> Jacek
> 
> On 10/28/19 2:22 PM, Jacek Anaszewski wrote:
>> 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].
> 
> Ack but this probably would not be multicolor either based on LED node
> naming conventions.

Why? We still have LED color section in the LED name pattern.
And for multicolor LEDs this would make sense.

>>> +-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.
>>
> Replies were given on the 13/19 patch.

AFAIR they referred to channel mapping but my request related to
replacing list with array was rather more general. We simply don't
need a list for fixed set of colors.

-- 
Best regards,
Jacek Anaszewski