Re: [PATCH v3 2/6] of: Add helper for mapping device node to logical CPU number

[Suzuki K Poulose]

On 27/07/17 16:48, Rob Herring wrote:
> Please use get_maintainers and cc the right people/lists.

Sorry about that, will fix it.

> +Frank, DT list
>
> On Thu, Jul 27, 2017 at 10:10 AM, Suzuki K Poulose
> <suzuki.poulose@xxxxxxx> wrote:
> > Add a helper to map a device node to a logical CPU number to avoid
> > duplication. Currently this is open coded in different places (e.g
> > gic-v3, coresight). The helper tries to map device node to a "possible"
> > logical CPU id, which may not be online yet. It is the responsibility
> > of the user to make sure that the CPU is online. The helper uses
> > of_get_cpu_node() which uses arch specific backends to match the phyiscal
> > ids.
> >
> > Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
> > Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> >  drivers/of/base.c         | 26 ++++++++++++++++++++++++++
> >  include/linux/of_device.h |  7 +++++++
> >  2 files changed, 33 insertions(+)
> >
> > diff --git a/drivers/of/base.c b/drivers/of/base.c
> > index 686628d..0b01515 100644
> > --- a/drivers/of/base.c
> > +++ b/drivers/of/base.c
> > @@ -420,6 +420,32 @@ struct device_node *of_get_cpu_node(int cpu, unsigned int *thread)
> >  EXPORT_SYMBOL(of_get_cpu_node);
> >
> >  /**
> > + * of_device_node_get_cpu: Get the logical CPU number for a given device_node
> > + *
> > + * @cpu_node: Pointer to the device_node for CPU.
> > + *
> > + * Returns the logical CPU number of the given CPU device_node.
> > + * Returns >= nr_cpu_ids if CPU is not found.
>
> Wouldn't negative be easier to test for? Then the caller doesn't need
> to know nr_cpu_ids.

I followed the conventions used by cpu_mask upon error here. But, we
could return -ENODEV upon failure here.
> > + */
> > +int of_device_node_get_cpu(struct device_node *cpu_node)
>
> of_device_* is for functions operating on struct device. So find
> another name. of_cpu_node_to_id perhaps.
>
> _get functions generally imply incrementing ref counts which you are
> not doing here.

OK, I can switch to of_cpu_node_to_id().

> > +{
> > +       int cpu;
> > +       bool found = false;
> > +       struct device_node *np;
> > +
> > +       for_each_possible_cpu(cpu) {
> > +               np = of_get_cpu_node(cpu, NULL);
> > +               found = (cpu_node == np);
> > +               of_node_put(np);
> > +               if (found)
> > +                       break;
> > +       }
> > +
> > +       return cpu;
> > +}
> > +EXPORT_SYMBOL(of_device_node_get_cpu);
> > +
> > +/**
> >   * __of_device_is_compatible() - Check if the node matches given constraints
> >   * @device: pointer to node
> >   * @compat: required compatible string, NULL or "" for any match
> > diff --git a/include/linux/of_device.h b/include/linux/of_device.h
> > index b4ad8b4..00a4ba9 100644
> > --- a/include/linux/of_device.h
> > +++ b/include/linux/of_device.h
> > @@ -40,6 +40,8 @@ extern int of_device_request_module(struct device *dev);
> >  extern void of_device_uevent(struct device *dev, struct kobj_uevent_env *env);
> >  extern int of_device_uevent_modalias(struct device *dev, struct kobj_uevent_env *env);
> >
> > +extern int of_device_node_get_cpu(struct device_node *np);
> > +
>
> Wrong place for this.

How about include/linux/of.h ?

Suzuki