PWM...

[Olof Johansson]

On Sun, Jan 19, 2014 at 11:08 AM, Arnd Bergmann <arnd at arndb.de> wrote:
> On Sunday 19 January 2014 11:03:24 Olof Johansson wrote:
>> >
>> > Yes, because iMX6 specifies #pwm-cells as 2, there's no flags able to
>> > be specified in the pwms declaration in pwmleds.  So that doesn't work.
>> > There's no property to tell pwmleds that it should use inverted sense
>> > either.
>>
>> Adding a property for active-low to the pwm-leds binding would be
>> easy, and backwards compatible. I'm surprised the original binding
>> didn't specify it. The leds-pwm driver already seems to support it for
>> C-configured instances.
>>
>> I'm also surprised that the imx pwm driver even has a #pwm-cells of
>> two, since the driver only supports one output. It'd be nice if they
>> had allocated the extra cell for flags, but it's hard to change now,
>> unless you do a new binding/compatible value and deprecate the old one.
>
> Actually I think it's not that hard to change: The binding can specify
> that either #pwm-cells=<2> or #pwm-cells=<3> is supported, and the
> driver extended to handle both cases. This would maintain backwards
> compatibility for old dtb files, though no forward compatibility for
> new dtb files with old kernels.

Ah, yes, if you add a cell that can be done. There'll still be the
"dead" first cell that will always be 0, but that's alright.


-Olof