On Thu, Mar 31, 2016 at 09:07:09AM +0200, Boris Brezillon wrote: > Hi Guenter, > > On Wed, 30 Mar 2016 15:52:44 -0700 > Guenter Roeck <[email protected]> wrote: > > > On Wed, Mar 30, 2016 at 10:03:31PM +0200, Boris Brezillon wrote: > > > The PWM framework has clarified the concept of reference PWM config > > > (the platform dependent config retrieved from the DT or the PWM > > > lookup table) and real PWM state. > > > > > > Use pwm_get_args() when the PWM user wants to retrieve this reference > > > config and not the current state. > > > > > > This is part of the rework allowing the PWM framework to support > > > hardware readout and expose real PWM state even when the PWM has > > > just been requested (before the user calls pwm_config/enable/disable()). > > > > > > Signed-off-by: Boris Brezillon <[email protected]> > > > --- > > > drivers/hwmon/pwm-fan.c | 19 +++++++++++++------ > > > 1 file changed, 13 insertions(+), 6 deletions(-) > > > > > > diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c > > > index 3e23003..82c5656 100644 > > > --- a/drivers/hwmon/pwm-fan.c > > > +++ b/drivers/hwmon/pwm-fan.c > > > @@ -40,15 +40,18 @@ struct pwm_fan_ctx { > > > > > > static int __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm) > > > { > > > + struct pwm_args pargs = { }; > > > > Hi Boris, > > > > I guess I am missing some context; sorry for that. Unfortunately, > > I did not easily find an explanation, so please bear with me. > > > > Two questions: Why do we need a local copy of struct pwm_args instead > > of a pointer to it ? If it can change while being used, isn't it > > inconsistent anyway ? > > It cannot change after pwm_get() is called. For the reason behind > prototype: I just followed the Thierry's proposal, but I'm perfectly > fine returning a const struct pwm_args pointer intead of passing > pwm_args as a parameter. > > Thierry, what's your opinion?
I do prefer the current variant because it is more consistent with the
new atomic API, even if not strictly necessary because of the immutable
data.
> > Also, assuming the local copy is necessary, why initialize pargs ?
> > After all, pwm_get_args() just overwrites it.
>
> It's a leftover from a previous version where pwm_get_args was
> implemented this way:
>
> static inline void pwm_get_args(pwm, args)
> {
> if (pwm)
> *args = pwm->args
> }
>
> and this implementation was generating a lot of 'uninitialized
> variable' warnings.
>
> I just decided to drop the 'if (pwm)' test, because, IMO, this
> should be checked way before calling pwm_get_args() is called.
Sounds fine to me.
Thierry
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