[PATCH] of: Make of_find_node_by_path() handle /aliases

[PATCH] of: Make of_find_node_by_path() handle /aliases

[Pantelis Antoniou]

Make of_find_node_by_path() handle aliases as prefixes.

Originally by David Daney <ddaney-M3mlKVOIwJVv6pq1l3V1OdBPR1lH4CV8@public.gmane.org>, but
reworked according to remark by Grant Likely.

Handles all cases without allocating memory as requested by
Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

Signed-off-by: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/w@public.gmane.org>
---
 drivers/of/base.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 65 insertions(+), 4 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 7083fad..19bcdb4 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -773,22 +773,83 @@ EXPORT_SYMBOL(of_get_child_by_name);
 /**
  *	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.
  */
 struct device_node *of_find_node_by_path(const char *path)
 {
-	struct device_node *np = of_allnodes;
+	struct device_node *np = NULL;
+	int len;
+	const char *p = NULL;
+	struct property *prop;
 	unsigned long flags;
 
+	/* under lock (not very nice) */
 	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))
+
+	len = strlen(path);
+
+	/* path begins with an alias */
+	if (path[0] != '/') {
+
+		/* now find the relative path (if any)*/
+		p = strchr(path, '/');
+		if (p != NULL)
+			len = p - path;
+
+		/* of_aliases must not be NULL */
+		if (!of_aliases)
+			goto out;
+
+		/* find matching alias */
+		for_each_property_of_node(of_aliases, prop)
+			if (strlen(prop->name) == len &&
+					strncmp(prop->name, path, len) == 0)
+				break;
+
+		/* not found; bail */
+		if (prop == NULL)
+			goto out;
+
+		path = prop->value;
+	}
+
+	/* path lookup */
+	for_each_of_allnodes(np) {
+
+		if (!np->full_name)
+			continue;
+
+		if (p == NULL) {
+			/* full component */
+			if (strcasecmp(np->full_name, path) != 0)
+				continue;
+		} else {
+			/* last component (including '/') */
+			if (strncasecmp(np->full_name, path, len) != 0)
+				continue;
+
+			if (strcasecmp(np->full_name + len, p) != 0)
+				continue;
+		}
+
+		if (of_node_get(np))
 			break;
 	}
+
+out:
 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
+
 	return np;
 }
 EXPORT_SYMBOL(of_find_node_by_path);
-- 
1.7.12

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Re: [PATCH] of: Make of_find_node_by_path() handle /aliases

[Stephen Warren]

On 03/18/2014 03:52 PM, Pantelis Antoniou wrote:
> Make of_find_node_by_path() handle aliases as prefixes.
> 
> Originally by David Daney <ddaney-M3mlKVOIwJVv6pq1l3V1OdBPR1lH4CV8@public.gmane.org>, but
> reworked according to remark by Grant Likely.
> 
> Handles all cases without allocating memory as requested by
> Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

Why not just introduce a new function of_find_node_by_alias()? A single
unified function would make sense if the function did something like:
(1) find my path, and return if found (2) if not found, fall back to
searching /aliases. However, since this modified function takes 2
separate formats of input path based on whether it should search for an
alias or not, it seems like 2 separate functions would be a better API.
Perhaps the new API should simply be a wrapper around
of_find_node_by_path, once the alias has been found?
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Re: [PATCH] of: Make of_find_node_by_path() handle /aliases

[Grant Likely]

On Tue, Mar 18, 2014 at 9:52 PM, Pantelis Antoniou
<pantelis.antoniou@konsulko.com> wrote:
> Make of_find_node_by_path() handle aliases as prefixes.
>
> Originally by David Daney <ddaney@caviumnetworks.com>, but
> reworked according to remark by Grant Likely.
>
> Handles all cases without allocating memory as requested by
> Grant Likely <grant.likely@linaro.org>
>
> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>

I posted a patch that does the same thing with a different method just
a few days ago:

http://www.spinics.net/lists/devicetree/msg26336.html

The above patch also has the advantage of being a more efficient search.

g.

> ---
>  drivers/of/base.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 65 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 7083fad..19bcdb4 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -773,22 +773,83 @@ EXPORT_SYMBOL(of_get_child_by_name);
>  /**
>   *     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.
>   */
>  struct device_node *of_find_node_by_path(const char *path)
>  {
> -       struct device_node *np = of_allnodes;
> +       struct device_node *np = NULL;
> +       int len;
> +       const char *p = NULL;
> +       struct property *prop;
>         unsigned long flags;
>
> +       /* under lock (not very nice) */
>         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))
> +
> +       len = strlen(path);
> +
> +       /* path begins with an alias */
> +       if (path[0] != '/') {
> +
> +               /* now find the relative path (if any)*/
> +               p = strchr(path, '/');
> +               if (p != NULL)
> +                       len = p - path;
> +
> +               /* of_aliases must not be NULL */
> +               if (!of_aliases)
> +                       goto out;
> +
> +               /* find matching alias */
> +               for_each_property_of_node(of_aliases, prop)
> +                       if (strlen(prop->name) == len &&
> +                                       strncmp(prop->name, path, len) == 0)
> +                               break;
> +
> +               /* not found; bail */
> +               if (prop == NULL)
> +                       goto out;
> +
> +               path = prop->value;
> +       }
> +
> +       /* path lookup */
> +       for_each_of_allnodes(np) {
> +
> +               if (!np->full_name)
> +                       continue;
> +
> +               if (p == NULL) {
> +                       /* full component */
> +                       if (strcasecmp(np->full_name, path) != 0)
> +                               continue;
> +               } else {
> +                       /* last component (including '/') */
> +                       if (strncasecmp(np->full_name, path, len) != 0)
> +                               continue;
> +
> +                       if (strcasecmp(np->full_name + len, p) != 0)
> +                               continue;
> +               }
> +
> +               if (of_node_get(np))
>                         break;
>         }
> +
> +out:
>         raw_spin_unlock_irqrestore(&devtree_lock, flags);
> +
>         return np;
>  }
>  EXPORT_SYMBOL(of_find_node_by_path);
> --
> 1.7.12
>