[PATCH v2] clk: __clk_set_parent: set uninitialized variable

[rnayak@ti.com (Rajendra Nayak)]

On Monday 02 July 2012 01:11 PM, Marc Kleine-Budde wrote:
> This patch fixes the following 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]
>
> which has been introduced with commit:
>
>      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 patch applies to linux-3.5-rc5
>
> Cc: Rajendra Nayak<rnayak@ti.com>
> Signed-off-by: Marc Kleine-Budde<mkl@pengutronix.de>
> ---
> Hello,
>
> here an updated version. Changes since v1:
> - Set i to clk->num_parents as Uwe pointed out.

I started looking at how to avoid this initing
of i to clk->parents (which is correct for the logic
used below, but somehow seems error prone if someone
happens to change the logic without noticing the init
part)
This is what I came up with, not tested at all, but
worth considering if Mike dislikes the idea of initing
i to clk->parents.

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index dcbe056..af737cc 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1067,26 +1067,23 @@ 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",

regards,
Rajendra

>
> regards, Marc
>
>   drivers/clk/clk.c |    6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index dcbe056..9a75635 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1068,13 +1068,15 @@ 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)
> +	if (clk->parents) {
>   		for (i = 0; i<  clk->num_parents; i++)
>   			if (clk->parents[i] == parent)
>   				break;
> -	else
> +	} else {
> +		i = clk->num_parents
>   		clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents),
>   								GFP_KERNEL);
> +	}
>
>   	/*
>   	 * find index of new parent clock using string name comparison