Re: [PATCH 1/5] cpufreq: Define cpufreq_set_drv_attr_files() to add per CPU sysfs attributes

Lukasz Majewski
2013-06-06T08:58:14Z

Hi Viresh,

> On 6 June 2013 12:37, Lukasz Majewski <l.majewski@samsung.com> wrote:
>
> > Subject: cpufreq: Define cpufreq_set_drv_attr_files() to add per
> > CPU sysfs attributes
>
> Its not per-cpu. We just add it for policy->cpu and other routines
> actually create links.
>
> > The cpufreq_set_drv_attr_files() function creates sysfs file entry
> > for each available CPU. With it in place it is possible to add
> > different set of attributes without code duplication.
>
> Not for each available cpu but are linked to a policy->kobj and so
> shows up on each policy->cpus.

Yes, you are right here. Thanks for detailed explanation. Being
"per-cpu" comes from kobj embedded at policy, which has information
about cpus affected.

>
> > Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
> > Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>
> > ---
> > drivers/cpufreq/cpufreq.c | 23 +++++++++++++++--------
> > 1 file changed, 15 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 1b8a48e..ca74e27 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -730,12 +730,23 @@ static int cpufreq_add_dev_symlink(unsigned
> > int cpu, return ret;
> > }
> >
> > +static int cpufreq_set_drv_attr_files(struct cpufreq_policy
> > *policy,
> > + struct freq_attr **drv_attr)
> > +{
> > + while ((drv_attr) && (*drv_attr)) {
> > + if (sysfs_create_file(&policy->kobj,
> > &((*drv_attr)->attr)))
> > + return 1;
>
> You are changing the semantics here. We used to return error
> value from sysfs_create_file() and you are returning 1.

Yes, correct. The ret from sysfs_create_file shall be returned.
Returning 1 causes information lost.

>
> > + drv_attr++;
>
> If drv_attr was valid initially, then drv_attr++ can't make it NULL.
> So, we don't need to check validity of drv_attr for every loop.

I'm confused here.

So you want to check dev_attr for NULL just after:
drv_attr = cpufreq_driver->attr;
if (!drv_attr)
goto error;

and skip the check at the while loop:
while ((drv_attr) && (*drv_attr))

to

while ((*drv_attr))

Am I correct?

--
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group