linux-kernel - Re: [PATCH 1/2] leds: ktd20xx: Add the KTD20xx family of the RGB LEDs driver from Kinetic

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Message-ID: <20211109232930.GB26764@amd>
Date:   Wed, 10 Nov 2021 00:29:31 +0100
From:   Pavel Machek <pavel@....cz>
To:     Florian Eckert <fe@....tdt.de>
Cc:     robh+dt@...nel.org, Eckert.Florian@...glemail.com,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] leds: ktd20xx: Add the KTD20xx family of the RGB
 LEDs driver from Kinetic

hi!

> Introduce the KTD2061/58/59/60 RGB LEDs driver. The difference in these
> parts are the address number on the I2C bus the device is listen on.
> 
> All KT20xx device could control up to 12 LEDs. The chip can be operated
> in two variants.

How are the variants selected?

> Variant 1:
> The device has the ability to group LED outputs into two banks so that
> the two LED banks can be controlled with the same color. This could not
> be done via the LEDs 'sysfs' entry because of the limitation on the color
> register count. The color of the two banks can be configured via device
> 'sysfs' entry for all LEDs at once [current_color0|current_color1].
> Which color the LED is to be used can be set via the 'sysfs' of the
> individual LEDs via the 'multi_intensity' file. Valid values for the
> colors (RGB) are 0 | 1. The value 0 selects the color register 0 and the
> value 1 selects the color register 1.

So... you can select two colors (current_color0, current_color1), and
then then each of the 12 LEDs get one of those colors. What about
intensities? Can brightness be set arbitrarily for each LED?

> Variant 2:
> The device can also set the LED color independently. Since the chip only
> has two color registers, but we want to control the 12 LEDs
> independently via the 'led-class-multicolour' sysfs entry,
> the full RGB color depth cannot be used. Due to this limitation, only 7
> colors and the color black (off) can be set. To use this mode the color
> registers must be preset via the device tree or the device 'sysfs'. The
> color registers 0 must be preset with 0x00 (Red=0x00 Green=0x00 Blue=0x00).
> The color register1 should be preset all with the same value. This value
> depends on which light intensity is to be used in the setup.

So now we have 7 colors we can select from. That sounds better than
two colors. Why would we ever want to use variant 1?

Can we simply pretend this is 7 LED RGB driver?

> +/* Device attribute for color0 register
> + *
> + * The device attribute colour1 is intended to adjust the colour space.

Use color, not colour. Plus run this through checkpatch.

> + * The colour strength can be controlled via the current in 125uA steps.

I don't know what "colour strength" is.

> +/*
> + * The chip also offers the option "Fade rate".
> + */
> +static ssize_t faderate_show(struct device *dev, struct device_attribute *a,
> +		char *buf)
> +{
> +	struct i2c_client *client = to_i2c_client(dev);
> +	struct ktd20xx *chip = i2c_get_clientdata(client);
> +	unsigned int value;
> +
> +	mutex_lock(&chip->lock);
> +	regmap_field_read(chip->faderate, &value);
> +	mutex_unlock(&chip->lock);
> +
> +	return sprintf(buf, "%d\n", value);
> +}

That's way too hardware specific.

Best regards,
									Pavel
-- 
http://www.livejournal.com/~pavelmachek

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