Re: [PATCH v5 05/46] pwm: introduce the pwm_args concept

Boris Brezillon
2016-04-12T12:55:11Z

On Tue, 12 Apr 2016 14:20:29 +0200
Thierry Reding <thierry.reding@gmail.com> wrote:

> On Tue, Apr 12, 2016 at 02:04:12PM +0200, Boris Brezillon wrote:
> > On Tue, 12 Apr 2016 13:39:12 +0200
> > Thierry Reding <thierry.reding@gmail.com> wrote:
> >
> > > On Wed, Mar 30, 2016 at 10:03:28PM +0200, Boris Brezillon wrote:
> > > > Currently the PWM core mixes the current PWM state with the per-platform
> > > > reference config (specified through the PWM lookup table, DT definition or
> > > > directly hardcoded in PWM drivers).
> > > >
> > > > Create a pwm_args struct to store this reference config, so that PWM users
> > > > can differentiate the current config from the reference one.
> > > >
> > > > Patch all places where pwm->args should be initialized. We keep the
> > > > pwm_set_polarity/period() calls until all PWM users are patched to
> > > > use pwm_args instead of pwm_get_period/polarity().
> > >
> > > Perhaps a helper would be useful? Something like:
> > >
> > > static inline void
> > > pwm_apply_args(struct pwm_device *pwm, const struct pwm_args *args)
> > > {
> > > pwm_set_duty_cycle(pwm, args->duty_cycle);
> > > pwm_set_period(pwm, args->period);
> > > }
> > >
> > > ? That would make it slightly easier to get rid of it again after all
> > > clients have been converted.
> >
> > Sure. I'll add this helper.
> >
> > >
> > > With the exception of pwm-clps711x all of these args are set at of_xlate
> > > time (for DT) or from the lookup table in pwm_get() (for non-DT), so it
> > > might even be possible to move this call to the core, so that removal of
> > > it will be a one-liner.
> >
> > Not sure I get that one. Some drivers are implementing their own
> > ->of_xlate() method, how would you get rid of this pwm_apply_args() in
> > those custom implementations?
>
> I was proposing to have pwm_apply_args() called from the core.
> of_pwm_get() is where ->of_xlate() is called from, and the lookup table
> arguments would be applied in pwm_get(). Taking into account clps711x,
> which sets the arguments in ->request() it might be possible to simply
> call pwm_apply_args() from pwm_device_request(), since that's also
> called by all other request functions, even the legacy ones.
>
> That said, the amount of code to modify isn't that large, so I'm fine if
> you want to keep sprinkling the calls across multiple files, especially
> since it's temporary.

No, I'm fine addressing that, but I just don't get where you'd get the
pwm_args to apply. Do you suggest to pass 'struct pwm_args *' to the
->of_xlate() and ->request() methods?

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering