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Date: Fri, 16 May 2014 11:54:44 +0100
From: Grant Likely <grant.likely@...aro.org>
To: frowand.list@...il.com
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
David Daney <david.daney@...ium.com>,
Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Subject: Re: [PATCH 2/3] of: Make of_find_node_by_path() handle /aliases
On Thu, 15 May 2014 19:51:17 -0700, Frank Rowand <frowand.list@...il.com> wrote:
> On 5/13/2014 7:58 AM, Grant Likely 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]
> > Acked-by: Rob Herring <robh@...nel.org>
> > Signed-off-by: Grant Likely <grant.likely@...aro.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 6e240698353b..60089b9a3014 100644
> > --- a/drivers/of/base.c
> > +++ b/drivers/of/base.c
> > @@ -771,9 +771,38 @@ 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;
>
> (!len) is true if the the final character of the path passed into of_find_node_by_path()
> was "/". Strictly speaking, ->full_name will never end with "/", so the return value
> should be NULL, indicating that the match fails.
Ah, good catch. I should add a test case for that.
>
> > +
> > + 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++;
>
> Why go to the effort of finding the final component of child->full_name instead
> of just using child->name?
Because child->name and the final component of child->full_name is not
the same thing. child->name has the unit address stripped off. It is
part of how OpenFirmware expects to be used. New drivers are never
supposed to be matching by node name, but I don't currently have a good
way to go through any driver depending on the OpenFirmware behaviour.
Ideally I'd like to get rid of the difference.
>
> > + 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
>
> Delete the old @path description.
Oops, thanks.
>
>
> > + * 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.
> > @@ -781,13 +810,36 @@ 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;
> >
>
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