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