On Fri, 10 Jun 2016, Thierry Reding wrote:

On Fri, Jun 10, 2016 at 03:06:35PM +0100, Lee Jones wrote:

quoted

On Fri, 10 Jun 2016, Thierry Reding wrote:

quoted

quoted

quoted

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The second documentation adaption entails adding support for PWM
capture devices.  A new clock is required as well as an IRQ line.
We're also adding a new property similar to the one described
above, but for capture channels.  Typically, there will be less
capture channels than PWM-out, since all channels have the latter
capability, but only some have capture support.

Humm, sounds like all of this should be implied from compatible strings.

You mean have a bunch of of_machine_is_compatibles() scattered around?

I don't understand why you need this at all. Quite frankly I don't even
know why st,pwm-num-devs exists. I probably missed it back at the time.
Usually, like Rob suggests, this should be inferred from the compatible
string. One commonly used way to avoid scattering explicit checks for
the compatible string is to add this information to the of_device_id
table. See a bunch of existing drivers for reference.

Yes, I am aware of the strategy, and happy to oblige if this is your
suggestion.  I'll move all platform data into the driver and eradicate
the DT properties.

Great!

Sorry it's taken so long to get back around to this.

So I just had a crack at implementing this solution and ran into
issues.  Unfortunately, the configuration isn't easy to describe using
compatible strings.

Unless we are prepared to have strings like:

  st,sti-pwm-stih407-pwm0
  st,sti-pwm-stih407-pwm1
  st,sti-pwm-stih416-pwm0
  st,sti-pwm-stih416-pwm1

Or perhaps:

  st,sti-pwm-4out-2cpt
  st,sti-pwm-1out-1cpt

... since some of the PWMs have an odd number of OUT and CPT
channels/devices.  In my opinion however, this is ugly.  I don't think
we do this for any other type of channel/device/port etc, do we?

Personally I think there isn't anything wrong with having DT
properties describing how many channels/devices there are, but I'm
okay with whatever you both decide.  No skin of my nose really. :)

What say you?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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