Message-ID: <03deb117-4bd4-b636-cbc9-4634afc73e78@gmail.com>
Date:   Sat, 28 Sep 2019 12:09:38 +0200
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Dan Murphy <dmurphy@...com>, pavel@....cz
Cc:     linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 05/15] leds: multicolor: Introduce a multicolor class
 definition

Dan,

On 9/26/19 1:52 PM, Dan Murphy wrote:
> Jacek
> 
> On 9/25/19 4:12 PM, Jacek Anaszewski wrote:
>> Dan,
>>
>> On 9/25/19 7:46 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@...com>
>>> ---
>>>   drivers/leds/Kconfig                 |  10 ++
>>>   drivers/leds/Makefile                |   1 +
>>>   drivers/leds/led-class-multicolor.c  | 220 +++++++++++++++++++++++++++
>>>   include/linux/led-class-multicolor.h |  74 +++++++++
>>>   4 files changed, 305 insertions(+)
>>>   create mode 100644 drivers/leds/led-class-multicolor.c
>>>   create mode 100644 include/linux/led-class-multicolor.h
>>>
>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>> index 6e7703fd03d0..cfb1ebb6517f 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 2da39e896ce8..841038cfe35b 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..25371bd9a860
>>> --- /dev/null
>>> +++ b/drivers/leds/led-class-multicolor.c
>>> @@ -0,0 +1,220 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +// LED Multi Color class interface
>>> +// Copyright (C) 2019 Texas Instruments Incorporated -
>>> http://www.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"
>>> +
>>> +#define INTENSITY_NAME        "_intensity"
>>> +#define MAX_INTENSITY_NAME    "_max_intensity"
>>> +
>>> +void led_mc_calc_brightness(struct led_classdev_mc *mcled_cdev,
>>> +                enum led_brightness brightness,
>>> +                int brightness_val[])
>>> +{
>>> +    struct led_mc_color_entry *priv;
>>> +    int i = 0;
>>> +
>>> +    list_for_each_entry(priv, &mcled_cdev->color_list, list) {
>> I think we should have some way to let the caller know exact mapping
>> of brightness_val to color_id. Possibly LED mc core should provide
>> a helper to get color_id by color entry index.
> 
> Why would we need that?

To make LED mc API more straightforward and avoid making
clients wondering in what order colors will be assigned to array
elements. And finally forcing them to go and analyze LED mc core.

>> But this remark is actually more relevant to the place of calling.
>> I'll try to propose something there.
>>
>> And regarding brightness_val name - how about:
>>
>> s/brightness_val/brightness_component/ ?
> 
> component does not make sense to me in this context.  Actually
> brightness_val
> 
> does not make sense either since it is an adjusted intensity and
> brightness is passed in in the second arg
> 
> I think intensity_values make more sense.

Every variable carries some value. so this is meaningless.
Intensity OTOH can be confused with <color>_intensity, which
is not going to be written to the hardware, but used
as a factor for calculating final LED iout brightness.

The aim of the equation is to multiple the ratio of
color intensity to its max intensity by global brightness.
The resulting value is written to the hardware to set
brightness of a LED being one of the components producing
the final final combined color.

I had to come up with literal description of the equation
to facilitate devising better variable name :-)

Having the above, how about "color_component" ?

>>
>>
>>> +        brightness_val[i] = brightness *
>>> +                    priv->intensity / priv->max_intensity;

Now, looking closer at this equation it becomes obvious to me
why Pavel opted for common max_brightness: in case of
<color>_intensity == <color>_max_intensity we will get the result
equal to max_brightness. And this is problematic: think of a case when
calculated value will be greater than given <color>_max_intensity.
It will have to be limited the that constraint and will fail to
produce proper color combination.

As a solution I see limiting max_brightness to the lowest supported
brightness from the LEDs in the cluster.

>>> +        i++;
>>> +    }
>>> +}
>>> +EXPORT_SYMBOL_GPL(led_mc_calc_brightness);
>>> +
>>> +static ssize_t intensity_store(struct device *dev,
>>> +                struct device_attribute *intensity_attr,
>>> +                const char *buf, size_t size)
>>> +{
>>> +    struct led_mc_color_entry *priv = container_of(intensity_attr,
>>> +                            struct led_mc_color_entry,
>>> +                              intensity_attr);
>>> +    struct led_classdev *led_cdev = priv->mcled_cdev->led_cdev;
>>> +    unsigned long value;
>>> +    ssize_t ret;
>>> +
>>> +    mutex_lock(&led_cdev->led_access);
>>> +
>>> +    ret = kstrtoul(buf, 10, &value);
>>> +    if (ret)
>>> +        goto unlock;
>>> +
>>> +    if (value > priv->max_intensity) {
>>> +        ret = -EINVAL;
>>> +        goto unlock;
>>> +    }
>>> +
>>> +    priv->intensity = value;
>>> +    ret = size;
>>> +
>>> +unlock:
>>> +    mutex_unlock(&led_cdev->led_access);
>>> +    return ret;
>>> +}
>>> +
>>> +static ssize_t intensity_show(struct device *dev,
>>> +                  struct device_attribute *intensity_attr,
>>> +                  char *buf)
>>> +{
>>> +    struct led_mc_color_entry *priv = container_of(intensity_attr,
>>> +                            struct led_mc_color_entry,
>>> +                              intensity_attr);
>>> +
>>> +    return sprintf(buf, "%d\n", priv->intensity);
>>> +}
>>> +
>>> +static ssize_t max_intensity_show(struct device *dev,
>>> +                   struct device_attribute *max_intensity_attr,
>>> +                   char *buf)
>>> +{
>>> +    struct led_mc_color_entry *priv = container_of(max_intensity_attr,
>>> +                            struct led_mc_color_entry,
>>> +                              max_intensity_attr);
>>> +
>>> +    return sprintf(buf, "%d\n", priv->max_intensity);
>>> +}
>>> +
>>> +static struct attribute *led_color_attrs[] = {
>>> +    NULL,
>>> +};
>>> +
>>> +static struct attribute_group led_color_group = {
>>> +    .name = "colors",
>>> +    .attrs = led_color_attrs,
>>> +};
>>> +
>>> +static int led_multicolor_init_color(struct led_classdev_mc
>>> *mcled_cdev,
>>> +                     int color_id, int color_index)
>>> +{
>>> +    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 = 644;
>> Proper octal value should begin with 0.
>> But please use combinations of dedicated S_I* definitions
>> from include/uapi/linux/stat.h.
> 
> Using the S_I* causes checkpatch warnings
> 
> WARNING: Symbolic permissions 'S_IRUGO' are not preferred. Consider
> using octal permissions '0444'.
> #139: FILE: drivers/leds/led-class-multicolor.c:139:
> +    mc_priv->max_intensity_attr.attr.mode = S_IRUGO;

Ah, right. Anyway, you need to add leading 0.

>>
>>> +    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 = 444;
>>> +    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);
>>> +
>>> +max_intensity_err_out:
>>> +    kfree(max_intensity_file_name);
>>> +intensity_err_out:
>>> +    kfree(intensity_file_name);
>>> +    return ret;
>>> +}
>>> +
>>> +static int led_multicolor_init_color_dir(struct led_classdev_mc
>>> *mcled_cdev)
>>> +{
>>> +    struct led_classdev *led_cdev = mcled_cdev->led_cdev;
>>> +    int ret;
>>> +    int i, color_index = 0;
>>> +
>>> +    ret = sysfs_create_group(&led_cdev->dev->kobj, &led_color_group);
>>> +    if (ret)
>>> +        return ret;
>>> +
>>> +    for (i = 0; i < LED_COLOR_ID_MAX; i++) {
>>> +        if (test_bit(i, &mcled_cdev->available_colors)) {
>>> +            ret = led_multicolor_init_color(mcled_cdev, i,
>>> +                            color_index);
>> color_index is now unused AFAICS.
> 
> Ack
> 
>>
>>> +            if (ret)
>>> +                break;
>>> +
>>> +            color_index++;
>>> +        }
>>> +    }
>>> +
>>> +    return ret;
>>> +}
>>> +
>>> +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 ret;
>>> +
>>> +    if (!mcled_cdev)
>>> +        return -EINVAL;
>>> +
>>> +    led_cdev = mcled_cdev->led_cdev;
>>> +    INIT_LIST_HEAD(&mcled_cdev->color_list);
>>> +
>>> +    /* Register led class device */
>>> +    ret = led_classdev_register_ext(parent, led_cdev, init_data);
>>> +    if (ret)
>>> +        return ret;
>>> +
>>> +    return led_multicolor_init_color_dir(mcled_cdev);
>>> +}
>>> +EXPORT_SYMBOL_GPL(led_classdev_multicolor_register_ext);
>> Why devm_* versions are missing now?
> 
> I was using the led-class-flash.c as an example and that class does not
> have the devm_* versions either.

Why did you have them in v8 then?

> Tried to make the 2 child classes look the same.

We can fix the shortcomings while adding new code.

> If they are missing from the led-class-flash code then that needs to be
> fixed as well.

Well, yes.

>>
>>> +
>>> +void led_classdev_multicolor_unregister(struct led_classdev_mc
>>> *mcled_cdev)
>>> +{
>>> +    struct led_mc_color_entry *priv, *next;
>>> +
>>> +    if (!mcled_cdev)
>>> +        return;
>>> +
>>> +    list_for_each_entry_safe(priv, next, &mcled_cdev->color_list, list)
>>> +        list_del(&priv->list);
>>> +
>>> +    sysfs_remove_group(&mcled_cdev->led_cdev->dev->kobj,
>>> &led_color_group);
>>> +    led_classdev_unregister(mcled_cdev->led_cdev);
>>> +}
>>> +EXPORT_SYMBOL_GPL(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..280ba5a614b4
>>> --- /dev/null
>>> +++ b/include/linux/led-class-multicolor.h
>>> @@ -0,0 +1,74 @@
>>> +/* 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;
>>> +
>>> +struct led_mc_color_entry {
>>> +    struct led_classdev_mc *mcled_cdev;
>>> +
>>> +    struct device_attribute max_intensity_attr;
>>> +    struct device_attribute intensity_attr;
>>> +
>>> +    enum led_brightness max_intensity;
>>> +    enum led_brightness intensity;
>>> +
>>> +    struct list_head list;
>>> +
>>> +    int led_color_id;
>>> +};
>>> +
>>> +struct led_classdev_mc {
>>> +    /* led class device */
>>> +    struct led_classdev *led_cdev;
>>> +    struct list_head color_list;
>>> +
>>> +    unsigned long available_colors;
>>> +    int num_leds;
>>> +};
>>> +
>>> +static inline struct led_classdev_mc *lcdev_to_mccdev(
>>> +                        struct led_classdev *lcdev)
>>> +{
>>> +    return container_of(lcdev, struct led_classdev_mc, led_cdev);
>>> +}
>>> +
>>> +/**
>>> + * 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);
>>> +
>>> +#define led_classdev_multicolor_register(parent, mcled_cdev)        \
>>> +    led_classdev_multicolor_register_ext(parent, mcled_cdev, NULL)
>> Please turn it into inline.
> 
> Again same statement as above on the led-class-flash.  This is how this
> is defined there.
> 
> If that is not correct in the flash class then that needs to be fixed as
> well.

Did you see my patch fixing these things in leds.h [0]?
I just missed that problem in led-class-flash.h.

>>> +
>>> +/**
>>> + * 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 */
>>> +void led_mc_calc_brightness(struct led_classdev_mc *mcled_cdev,
>>> +                enum led_brightness brightness,
>>> +                int brightness_val[]);
>>> +
>>> +#endif    /* __LINUX_MULTICOLOR_LEDS_H_INCLUDED */
>>>
> 

[0]
https://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds.git/commit/?h=for-next&id=7c322056e3564da1b5bdc3f3cb79229582955eb2

-- 
Best regards,
Jacek Anaszewski

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