On 11/23/2012 10:44 AM, Peter Ujfalusi wrote:

Hi Grant,

On 11/23/2012 10:13 AM, Peter Ujfalusi wrote:

quoted

Hi Grant,

On 11/23/2012 08:55 AM, Grant Likely wrote:

quoted

Ugh. and this is why I wanted the PWM and GPIO subsystems to use the
same namespace and binding. <grumble, mutter> But that's not your fault.

It's pretty horrible to have a separate translator node to convert a PWM
into a GPIO (with output only of course). The gpio properties should
appear directly in the PWM node itself and the translation code should
be in either the pwm or the gpio core. I don't think it should look like
a separate device.

Let me see if I understand your suggestion correctly. In the DT you suggest
something like this:

twl_pwmled: pwmled {
	compatible = "ti,twl4030-pwmled";
	#pwm-cells = <2>;
	#gpio-cells = <2>;
	gpio-controller;
};

After I thought about this.. Is this what we really want?
After all what we have here is a PWM generator used to emulate a GPIO signal.
The PWM itself can be used for driving a LED (standard LED or backlight and we
have DT bindings for these already), vibra motor, or other things.
If we combine the PWM with GPIO we should go and 'bloat' the DT node to also
include all sort of other uses of PWM at once?

IMHO it is better to keep them as separate things.
pwm node to describe the PWM generator,
separate nodes to describe it's uses like led, backlight, motor and gpio.

The difference here is that the LED, backlight, etc are all different
physical devices begin driven by the pwm pin, so it makes sense to have a
device tree node for them, while using the pwm as gpio is just a different
function of the same physical pin.  So in a sense the pwm controller also
becomes a gpio controller. I like the idea of the pwm core automatically
instantiating a pwm-gpo device if it sees a gpio-controller property in the
pwm device devicetree node.

- Lars