Re: [PATCH] bus: arm-cci: constify attribute_group structures.

[Suzuki K Poulose]

On 06/07/17 05:53, Arvind Yadav wrote:
> Hi,
>
>
> On Wednesday 05 July 2017 09:33 PM, Suzuki K Poulose wrote:
> > On 03/07/17 08:46, Arvind Yadav wrote:
> > > attribute_groups are not supposed to change at runtime. All functions
> > > working with attribute_groups provided by <linux/sysfs.h> work with const
> > > attribute_group. So mark the non-const structs as const.
> > >
> > > Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
> > > ---
> > >  drivers/bus/arm-cci.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c
> > > index c49da15..64c75d2 100644
> > > --- a/drivers/bus/arm-cci.c
> > > +++ b/drivers/bus/arm-cci.c
> > > @@ -1445,16 +1445,16 @@ static ssize_t pmu_cpumask_attr_show(struct device *dev,
> > >      NULL,
> > >  };
> > >
> > > -static struct attribute_group pmu_attr_group = {
> > > +static const struct attribute_group pmu_attr_group = {
> > >      .attrs = pmu_attrs, /*This can be const*/
> > >  };
> > >
> > > -static struct attribute_group pmu_format_attr_group = {
> > > +static const struct attribute_group pmu_format_attr_group = {
> > >      .name = "format",
> > >      .attrs = NULL,        /* Filled in cci_pmu_init_attrs */
> > >  };
> >
> >
> >
> > > -static struct attribute_group pmu_event_attr_group = {
> > > +static const struct attribute_group pmu_event_attr_group = {
> > >      .name = "events",
> > >      .attrs = NULL,        /* Filled in cci_pmu_init_attrs */
> > >  };
> >
> > I think we cannot make these const, as the attrs field gets filled in at runtime, indicated
> > by the comments next to them.
>     Yes, Your are right. It's filled at run time.
>         pmu_event_attr_group.attrs = model->event_attrs;
>         pmu_format_attr_group.attrs = model->format_attrs;
>     can we make pmu_attr_group as const.? It's already initialized.
>     If you are ok with this please let me know. I can push updated patch.

Yes, you can do that.

Or you could go a step ahead and create per-model pmu_attr_groups[], with shared
pmu_attr_group and per-model event/format groups and tie it to the model description
and make everything const.

i.e,

static const struct attribute_group cci5xx_pmu_attr_groups[] = {
	&pmu_attr_group,
	&cci5xx_format_attr_group,
	&cci5xx_event_attr_group,
	NULL,
};

static const struct attribute_group cci400r0_pmu_attr_groups = {
	&pmu_attr_group,
	&cci400_pmu_format_attr_group,
	&cci400_pmu_event_attr_group,
	NULL,
};

static const struct attribute_group cci400r1_pmu_attr_groups = {
	&pmu_attr_group,
	&cci400_pmu_format_attr_group,
	&cci400r1_pmu_event_attr_group,
	NULL,
};

and then do :

cci_pmu->pmu = (struct pmu) {
	....
	.attr_groups = model->attr_groups,
};

Suzuki