linux-kernel - Re: [RFC v3 3/3] of: Make of_find_node_by

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Message-Id: <20140315123331.7351DC40A1B@trevor.secretlab.ca>
Date:	Sat, 15 Mar 2014 12:33:31 +0000
From:	Grant Likely <grant.likely@...aro.org>
To:	Rob Herring <robherring2@...il.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
	David Daney <david.daney@...ium.com>
Subject: Re: [RFC v3 3/3] of: Make of_find_node_by_path() handle /aliases

On Fri, 14 Mar 2014 16:39:38 -0500, Rob Herring <robherring2@...il.com> wrote:
> On Fri, Mar 14, 2014 at 12:11 PM, Grant Likely <grant.likely@...aro.org> wrote:
> > Make of_find_node_by_path() handle aliases as prefixes. To make this
> > work the name search is refactored to search by path component instead
> > of by full string. This should be a more efficient search, and it makes
> > it possible to start a search at a subnode of a tree.
> >
> > Signed-off-by: David Daney <david.daney@...ium.com>
> > Signed-off-by: Pantelis Antoniou <pantelis.antoniou@...sulko.com>
> > [grant.likely: Rework to not require allocating at runtime]
> > Signed-off-by: Grant Likely <grant.likely@...aro.org>
> 
> I should have read the comments before trying to figure out why you
> had that "pointless" recursion...

Hi Rob,

Thanks for the review. However, I'm a little slow this morning and I
don't understand what you mean. Did I miss an early comment?

g.

> 
> Acked-by: Rob Herring <robh@...nel.org>
> 
> > ---
> >  drivers/of/base.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++----
> >  1 file changed, 56 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/of/base.c b/drivers/of/base.c
> > index 7083fad079a6..b8b673526dbd 100644
> > --- a/drivers/of/base.c
> > +++ b/drivers/of/base.c
> > @@ -770,9 +770,38 @@ struct device_node *of_get_child_by_name(const struct device_node *node,
> >  }
> >  EXPORT_SYMBOL(of_get_child_by_name);
> >
> > +static struct device_node *__of_find_node_by_path(struct device_node *parent,
> > +                                               const char *path)
> > +{
> > +       struct device_node *child;
> > +       int len = strchrnul(path, '/') - path;
> > +
> > +       if (!len)
> > +               return parent;
> > +
> > +       for_each_child_of_node(parent, child) {
> > +               const char *name = strrchr(child->full_name, '/');
> > +               if (WARN(!name, "malformed device_node %s\n", child->full_name))
> > +                       continue;
> > +               name++;
> > +               if (strncmp(path, name, len) == 0 && (strlen(name) == len))
> > +                       return child;
> > +       }
> > +       return NULL;
> > +}
> > +
> >  /**
> >   *     of_find_node_by_path - Find a node matching a full OF path
> >   *     @path:  The full path to match
> > + *     @path: Either the full path to match, or if the path does not
> > + *            start with '/', the name of a property of the /aliases
> > + *            node (an alias).  In the case of an alias, the node
> > + *            matching the alias' value will be returned.
> > + *
> > + *     Valid paths:
> > + *             /foo/bar        Full path
> > + *             foo             Valid alias
> > + *             foo/bar         Valid alias + relative path
> >   *
> >   *     Returns a node pointer with refcount incremented, use
> >   *     of_node_put() on it when done.
> > @@ -780,13 +809,36 @@ EXPORT_SYMBOL(of_get_child_by_name);
> >  struct device_node *of_find_node_by_path(const char *path)
> >  {
> >         struct device_node *np = of_allnodes;
> > +       struct property *pp;
> >         unsigned long flags;
> >
> > +       /* The path could begin with an alias */
> > +       if (*path != '/') {
> > +               char *p = strchrnul(path, '/');
> > +               int len = p - path;
> > +
> > +               /* of_aliases must not be NULL */
> > +               if (!of_aliases)
> > +                       return NULL;
> > +
> > +               np = NULL;
> > +               for_each_property_of_node(of_aliases, pp) {
> > +                       if (strlen(pp->name) == len && !strncmp(pp->name, path, len)) {
> > +                               np = of_find_node_by_path(pp->value);
> > +                               break;
> > +                       }
> > +               }
> > +               if (!np)
> > +                       return NULL;
> > +               path = p;
> > +       }
> > +
> > +       /* Step down the tree matching path components */
> >         raw_spin_lock_irqsave(&devtree_lock, flags);
> > -       for (; np; np = np->allnext) {
> > -               if (np->full_name && (of_node_cmp(np->full_name, path) == 0)
> > -                   && of_node_get(np))
> > -                       break;
> > +       while (np && *path == '/') {
> > +               path++; /* Increment past '/' delimiter */
> > +               np = __of_find_node_by_path(np, path);
> > +               path = strchrnul(path, '/');
> >         }
> >         raw_spin_unlock_irqrestore(&devtree_lock, flags);
> >         return np;
> > --
> > 1.8.3.2
> >
> > --
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