Re: [Xen-devel] [PATCH 7/7] xen/arm: get the number of cpus from device tree

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 15 Nov 2012, Ian Campbell wrote:
> On Tue, 2012-11-13 at 15:42 +0000, Stefano Stabellini wrote:
> > diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> > index 3d1f0f4..5b6dab9 100644
> > --- a/xen/common/device_tree.c
> > +++ b/xen/common/device_tree.c
> > @@ -153,6 +153,25 @@ const char *device_tree_bootargs(const void *fdt)
> >      return prop->data;
> >  }
> >  
> > +int device_tree_cpus(const void *fdt)
> > +{
> > +    int node = 0, depth = 1;
> > +    int cpus = 0;
> > +
> > +    node = fdt_path_offset(fdt, "/cpus/cpu");
> > +    if ( node < 0 )
> > +        return 1; /* we have at least one cpu */
> > +
> > +    while ( node >= 0 && depth >= 0 ) {
> > +        if ( strncmp(fdt_get_name(fdt, node, NULL), "cpu", 3) )
> > +            continue;
> > +        node = fdt_next_node(fdt, node, &depth);
> > +        cpus++;
> 
> Do we not need to track the largest <n> for each cpu@<n> which we see,
> in order to handle systems with e.g. CPUs 0, 1, 4 & 5?

Actually the hardware ID is expressed by the <reg> propery.
Maybe we should set the corresponding ID in cpu_present_map from
device_tree_cpus?


> There are some helpers in device_tree.c to walk over trees like this,
> are none of them suitable?
 
Do you mean device_tree_node_matches?
Yes, I can use that instead of strncmp. I'll do that.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel