[PATCH] powerpc: Add/remove/update properties in firmware device tree

Add support for updating and removing device tree
properties.  Since we hand out pointers to properties with gay
abandon, we can't just free the property storage.  Instead we
move deleted, or the old copy of an updated property, to a
"dead properties" list.

Also note, its not feasable to kref device tree properties.
we call get_property() all over the kernel in a wild variety
of contexts.

One consequence of this change is that we now take a
read_lock(&devtree_lock) when doing get_property().

Signed-off-by: Dave Boutcher <sleddog@us.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 02e2115323e49b5f6d43fcd782cea4843c76527c..70057b63de2132b3d3a2c287e863c22044e6fe38 100644 (file)
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -1627,6 +1627,11 @@ static void of_node_release(struct kref *kref)
                kfree(prop->value);
                kfree(prop);
                prop = next;
+
+               if (!prop) {
+                       prop = node->deadprops;
+                       node->deadprops = NULL;
+               }
        }
        kfree(node->intrs);
        kfree(node->full_name);
@@ -1783,13 +1788,16 @@ unsigned char *get_property(struct device_node *np, const char *name,
 {
        struct property *pp;
 
+       read_lock(&devtree_lock);
        for (pp = np->properties; pp != 0; pp = pp->next)
                if (strcmp(pp->name, name) == 0) {
                        if (lenp != 0)
                                *lenp = pp->length;
-                       return pp->value;
+                       break;
                }
-       return NULL;
+       read_unlock(&devtree_lock);
+
+       return pp ? pp->value : NULL;
 }
 EXPORT_SYMBOL(get_property);
 
@@ -1823,4 +1831,82 @@ int prom_add_property(struct device_node* np, struct property* prop)
        return 0;
 }
 
+/*
+ * Remove a property from a node.  Note that we don't actually
+ * remove it, since we have given out who-knows-how-many pointers
+ * to the data using get-property.  Instead we just move the property
+ * to the "dead properties" list, so it won't be found any more.
+ */
+int prom_remove_property(struct device_node *np, struct property *prop)
+{
+       struct property **next;
+       int found = 0;
+
+       write_lock(&devtree_lock);
+       next = &np->properties;
+       while (*next) {
+               if (*next == prop) {
+                       /* found the node */
+                       *next = prop->next;
+                       prop->next = np->deadprops;
+                       np->deadprops = prop;
+                       found = 1;
+                       break;
+               }
+               next = &(*next)->next;
+       }
+       write_unlock(&devtree_lock);
+
+       if (!found)
+               return -ENODEV;
+
+#ifdef CONFIG_PROC_DEVICETREE
+       /* try to remove the proc node as well */
+       if (np->pde)
+               proc_device_tree_remove_prop(np->pde, prop);
+#endif /* CONFIG_PROC_DEVICETREE */
+
+       return 0;
+}
+
+/*
+ * Update a property in a node.  Note that we don't actually
+ * remove it, since we have given out who-knows-how-many pointers
+ * to the data using get-property.  Instead we just move the property
+ * to the "dead properties" list, and add the new property to the
+ * property list
+ */
+int prom_update_property(struct device_node *np,
+                        struct property *newprop,
+                        struct property *oldprop)
+{
+       struct property **next;
+       int found = 0;
+
+       write_lock(&devtree_lock);
+       next = &np->properties;
+       while (*next) {
+               if (*next == oldprop) {
+                       /* found the node */
+                       newprop->next = oldprop->next;
+                       *next = newprop;
+                       oldprop->next = np->deadprops;
+                       np->deadprops = oldprop;
+                       found = 1;
+                       break;
+               }
+               next = &(*next)->next;
+       }
+       write_unlock(&devtree_lock);
+
+       if (!found)
+               return -ENODEV;
 
+#ifdef CONFIG_PROC_DEVICETREE
+       /* try to add to proc as well if it was initialized */
+       if (np->pde)
+               proc_device_tree_update_prop(np->pde, newprop, oldprop);
+#endif /* CONFIG_PROC_DEVICETREE */
+
+       return 0;
+}

diff --git a/include/asm-powerpc/prom.h b/include/asm-powerpc/prom.h
index 329e9bf62260cd69c074430224b547855c70bd12..25d8d5974d19d063acb2feb0d00e1e8556a1aeec 100644 (file)
--- a/include/asm-powerpc/prom.h
+++ b/include/asm-powerpc/prom.h
@@ -87,6 +87,7 @@ struct device_node {
        char    *full_name;
 
        struct  property *properties;
+       struct  property *deadprops; /* removed properties */
        struct  device_node *parent;
        struct  device_node *child;
        struct  device_node *sibling;
@@ -164,6 +165,10 @@ extern int prom_n_size_cells(struct device_node* np);
 extern int prom_n_intr_cells(struct device_node* np);
 extern void prom_get_irq_senses(unsigned char *senses, int off, int max);
 extern int prom_add_property(struct device_node* np, struct property* prop);
+extern int prom_remove_property(struct device_node *np, struct property *prop);
+extern int prom_update_property(struct device_node *np,
+                               struct property *newprop,
+                               struct property *oldprop);
 
 #ifdef CONFIG_PPC32
 /*