Re: [PATCH v2 2/2] cpufreq: simplify setpolicy/target check in driver verification

[Zihuan Zhang]

在 2025/8/21 17:17, Viresh Kumar 写道:
> On 21-08-25, 17:00, Zihuan Zhang wrote:
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index a067b5447fe8..92633ff2c4f3 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -2908,6 +2908,8 @@ static int cpuhp_cpufreq_offline(unsigned int cpu)
> >   int cpufreq_register_driver(struct cpufreq_driver *driver_data)
> >   {
> >   	unsigned long flags;
> driver_data can be NULL here. It is checked at a later point.
Thanks for your feedback. I did think about the case where driver_data 
is NULL, but I didn’t think it through properly at the time.

You are right — this clearly can cause issues.

> > +	bool has_setpolicy = driver_data->setpolicy;
> This is a pointer and ..
>
> > +	bool has_target = driver_data->target_index || driver_data->target;
> .. this is bool.
>
> Their comparison will always fail. Did you actually try this with both
> setpolicy and target() set for a cpufreq driver to check if it really
> fails ?
>
> What you need is:
>
> 	bool has_setpolicy = !!driver_data->setpolicy;
Sorry about that. I only tested the case where driver registration succeeds.

Do you have any suggestions on how to better test or handle the cases 
where driver registration could fail?
> >   	int ret;
> >   
> >   	if (cpufreq_disabled())
> > @@ -2921,10 +2923,7 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
> >   		return -EPROBE_DEFER;
> >   
> >   	if (!driver_data || !driver_data->verify || !driver_data->init ||
> > -	    !(driver_data->setpolicy || driver_data->target_index ||
> > -		    driver_data->target) ||
> > -	     (driver_data->setpolicy && (driver_data->target_index ||
> > -		    driver_data->target)) ||
> > +	     (has_setpolicy == has_target) ||
> I would rather do:
>
> 	(!!driver_data->setpolicy == (driver_data->target_index || driver_data->target))

The current version of the code is much better and safer.

Thanks for pointing this out.

I will carefully test all cases, including potential failure paths, and 
send a next version accordingly.

> >   	     (!driver_data->get_intermediate != !driver_data->target_intermediate) ||
> >   	     (!driver_data->online != !driver_data->offline) ||
> >   		 (driver_data->adjust_perf && !driver_data->fast_switch))
> > --
> > 2.25.1