If we should reuse blink_set to control hw blink I need to understand 2
thing.

The idea to implement the function hw_control_configure was to provide
the triggers some way to configure the various blink_mode. (and by using
the cmd enum provide different info based on the return value)

The advised path from Marek is to make the changes in the trigger_data
and the LED driver will then use that to configure blink mode.

I need to call an example to explain my concern:
qca8k switch. Can both run in hardware mode and software mode (by
controlling the reg to trigger manual blink) and also there is an extra
mode to blink permanently at 4hz.

Now someone would declare the brightness_set to control the led
manually and blink_set (for the permanent 4hz blink feature)
So that's where my idea comes about introducting another function and
the fact that it wouldn't match that well with blink_set with some LED.

I mean if we really want to use blink_set also for this(hw_control), we
can consider adding a bool to understand when hw_control is active or not.
So blink_set can be used for both feature.

I don't see why we need the bool. The driver should know that speeds
it supports. If asked to do something it cannot do in the current mode
it should return either -EINVAL, or maybe -EOPNOTSUPP. Depending on
how to the trigger works, we might want -EOPNOTSUPP when in a hardware
offload mode, which gets returned to user space. If we are in a
software blinking mode -EINVAL, so that the trigger does the blinking
in software.

   Andrew