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Subject: Re: [PATCH v9 13/15] leds: lp55xx: Update the lp55xx to use the multi
 color framework
To:     Jacek Anaszewski <jacek.anaszewski@gmail.com>, <pavel@ucw.cz>
CC:     <linux-leds@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20190925174616.3714-1-dmurphy@ti.com>
 <20190925174616.3714-14-dmurphy@ti.com>
 <59e58ccf-84fb-5db7-5008-20afc7436d35@gmail.com>
 <64d00aab-501c-d709-94af-4747a27df098@ti.com>
 <35e25398-81de-3755-7979-72638a119c77@gmail.com>
From:   Dan Murphy <dmurphy@ti.com>
Message-ID: <74099f4d-5a90-3241-9c40-47ca6f0c9521@ti.com>
Date:   Mon, 30 Sep 2019 11:31:53 -0500
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Jacek

On 9/29/19 8:01 AM, Jacek Anaszewski wrote:
> Dan,
>
> On 9/26/19 2:02 PM, Dan Murphy wrote:
>> Jacek
>>
>> On 9/25/19 5:00 PM, Jacek Anaszewski wrote:
>>> Dan,
>>>
>>> On 9/25/19 7:46 PM, Dan Murphy wrote:
>>>> Update the lp5523 to allow the use of the multi color framework.
>>>>
>>>> Signed-off-by: Dan Murphy <dmurphy@ti.com>
>>>> ---
>>>>    drivers/leds/Kconfig                      |   1 +
>>>>    drivers/leds/leds-lp5523.c                |  13 ++
>>>>    drivers/leds/leds-lp55xx-common.c         | 150 ++++++++++++++++++----
>>>>    drivers/leds/leds-lp55xx-common.h         |  11 ++
>>>>    include/linux/platform_data/leds-lp55xx.h |   6 +
>>>>    5 files changed, 157 insertions(+), 24 deletions(-)
>>>>
>>>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>>>> index 84f60e35c5ee..dc3d9f2194cd 100644
>>>> --- a/drivers/leds/Kconfig
>>>> +++ b/drivers/leds/Kconfig
>>>> @@ -377,6 +377,7 @@ config LEDS_LP50XX
>>>>    config LEDS_LP55XX_COMMON
>>>>        tristate "Common Driver for TI/National
>>>> LP5521/5523/55231/5562/8501"
>>>>        depends on LEDS_LP5521 || LEDS_LP5523 || LEDS_LP5562 ||
>>>> LEDS_LP8501
>>>> +    depends on LEDS_CLASS_MULTI_COLOR && OF
>>>>        select FW_LOADER
>>>>        select FW_LOADER_USER_HELPER
>>>>        help
>>>> diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
>>>> index d0b931a136b9..8b2cdb98fed6 100644
>>>> --- a/drivers/leds/leds-lp5523.c
>>>> +++ b/drivers/leds/leds-lp5523.c
>>>> @@ -791,6 +791,18 @@ static ssize_t store_master_fader_leds(struct
>>>> device *dev,
>>>>        return ret;
>>>>    }
>>>>    +static int lp5523_led_intensity(struct lp55xx_led *led, int chan_num)
>>> Why do we need this function? brightness op will not suffice?
>> I looked at this before sending it in.  This API adds the chan_num to
>> write to.
>>
>> The brightness_fn does not it takes it from the led structure.
>>
>>>> +{
>>>> +    struct lp55xx_chip *chip = led->chip;
>>>> +    int ret;
>>>> +
>>>> +    mutex_lock(&chip->lock);
>>>> +    ret = lp55xx_write(chip, LP5523_REG_LED_PWM_BASE + chan_num,
>>>> +             led->brightness);
>>>> +    mutex_unlock(&chip->lock);
>>>> +    return ret;
>>>> +}
>>>> +
>>>>    static int lp5523_led_brightness(struct lp55xx_led *led)
>>>>    {
>>>>        struct lp55xx_chip *chip = led->chip;
>>>> @@ -857,6 +869,7 @@ static struct lp55xx_device_config lp5523_cfg = {
>>>>        .max_channel  = LP5523_MAX_LEDS,
>>>>        .post_init_device   = lp5523_post_init_device,
>>>>        .brightness_fn      = lp5523_led_brightness,
>>>> +    .color_intensity_fn = lp5523_led_intensity,
>>>>        .set_led_current    = lp5523_set_led_current,
>>>>        .firmware_cb        = lp5523_firmware_loaded,
>>>>        .run_engine         = lp5523_run_engine,
>>>> diff --git a/drivers/leds/leds-lp55xx-common.c
>>>> b/drivers/leds/leds-lp55xx-common.c
>>>> index 44ced02b49f9..0e4b3a9d3047 100644
>>>> --- a/drivers/leds/leds-lp55xx-common.c
>>>> +++ b/drivers/leds/leds-lp55xx-common.c
>>>> @@ -136,9 +136,26 @@ static int lp55xx_set_brightness(struct
>>>> led_classdev *cdev,
>>>>    {
>>>>        struct lp55xx_led *led = cdev_to_lp55xx_led(cdev);
>>>>        struct lp55xx_device_config *cfg = led->chip->cfg;
>>>> +    int brightness_val[LP55XX_MAX_GROUPED_CHAN];
>>>> +    int ret;
>>>> +    int i;
>>>> +
>>>> +    if (led->mc_cdev.num_leds > 1) {
>>>> +        led_mc_calc_brightness(&led->mc_cdev,
>>>> +                       brightness, brightness_val);
>>>> +        for (i = 0; i < led->mc_cdev.num_leds; i++) {
>>>> +            led->brightness = brightness_val[i];
>>>> +            ret = cfg->color_intensity_fn(led,
>>>> +                              led->grouped_channels[i]);
>>> Now we will have three separate calls for each color component
>>> (and possibly sleeping on mutex on contention).
>>>
>>> Probably LED mc class use case will need a bit different design.
>>>
>>> Also, instead of grouped_channels we could possibly have
>>>
>>> led_mc_get_color_id(&led->mc_dev, i)
>> color_id and grouped_channels are not a 1:1 mapping
> OK, they're channel numbers.
>
>>> which would map entry position index to color_id.
>>>
>>> I will stop reviewing here and will continue after taking
>>> deeper look at this lp55xx design.
> I've analyzed that design in greater detail and have started
> to wonder why you can't pass two arrays to the new op:
> channel numbers and corresponding calculated channel intensities?


OK so I coded this up.  And there is not a clean way to do this since 
the channels and colors are not correlated between two structures.  In 
order to do this we would have to expand the grouped_channel and 
channel_color arrays in the lp55xx_led to LED_COLOR_ID_MAX and put the 
channel and color_component value in the position in the array that is 
associated with the color ID. Then the driver can loop through the 
available colors from the MC class and get the channel and 
color_component information.

Beyond that in coding this and thinking about the design it is better to 
have the lp55xx_common code to do all the heavy lifting and the children 
to just perform the action on the device itself. So doing the loop in 
the common code like we have now and calling the intensity_fn based on x 
number of LEDs.  The child subscriber to the common code should have to 
worry about the color it should only care about the channel and the value.

Dan