clk: fix parent validation in __clk_set_parent()
Rajendra Nayak [Tue, 3 Jul 2012 06:41:41 +0000 (11:41 +0530)]
The below commit introduced a bug in __clk_set_parent()
which could cause it to *skip* the parent validation
which makes sure the parent passed to the api is a valid
one.

    commit 7975059db572eb47f0fb272a62afeae272a4b209
    Author: Rajendra Nayak <rnayak@ti.com>
    Date:   Wed Jun 6 14:41:31 2012 +0530

        clk: Allow late cache allocation for clk->parents

This was identified by the following compiler warning..

    drivers/clk/clk.c: In function '__clk_set_parent':
    drivers/clk/clk.c:1083:5: warning: 'i' may be used uninitialized in this function [-Wuninitialized]

.. as reported by Marc Kleine-Budde.

There were various options discussed on how to fix this, one
being initing 'i' to clk->num_parents, but the below approach
was found to be more appropriate as it also makes the 'parent
validation' code simpler to read.

Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
Cc: stable@kernel.org

drivers/clk/clk.c

index dcbe056..9a1eb0c 100644 (file)
@@ -1067,26 +1067,24 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent)
 
        old_parent = clk->parent;
 
-       /* find index of new parent clock using cached parent ptrs */
-       if (clk->parents)
-               for (i = 0; i < clk->num_parents; i++)
-                       if (clk->parents[i] == parent)
-                               break;
-       else
+       if (!clk->parents)
                clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
                                                                GFP_KERNEL);
 
        /*
-        * find index of new parent clock using string name comparison
-        * also try to cache the parent to avoid future calls to __clk_lookup
+        * find index of new parent clock using cached parent ptrs,
+        * or if not yet cached, use string name comparison and cache
+        * them now to avoid future calls to __clk_lookup.
         */
-       if (i == clk->num_parents)
-               for (i = 0; i < clk->num_parents; i++)
-                       if (!strcmp(clk->parent_names[i], parent->name)) {
-                               if (clk->parents)
-                                       clk->parents[i] = __clk_lookup(parent->name);
-                               break;
-                       }
+       for (i = 0; i < clk->num_parents; i++) {
+               if (clk->parents && clk->parents[i] == parent)
+                       break;
+               else if (!strcmp(clk->parent_names[i], parent->name)) {
+                       if (clk->parents)
+                               clk->parents[i] = __clk_lookup(parent->name);
+                       break;
+               }
+       }
 
        if (i == clk->num_parents) {
                pr_debug("%s: clock %s is not a possible parent of clock %s\n",