Re: [PATCH] clk: remove unreachable code

[Mike Turquette <mturquette-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

Quoting Rajagopal Venkat (2013-01-08 22:29:48)
> while reparenting a clock, NULL check is done for clock in
> consideration and its new parent. So re-check is not required.
> If done, else part becomes unreachable.
> 
> Signed-off-by: Rajagopal Venkat <rajagopal.venkat-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
>  drivers/clk/clk.c |   13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 251e45d..1c4097c 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1040,7 +1040,6 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent)
>  {
>  #ifdef CONFIG_COMMON_CLK_DEBUG
>         struct dentry *d;
> -       struct dentry *new_parent_d;
>  #endif
>  
>         if (!clk || !new_parent)
> @@ -1048,22 +1047,14 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent)
>  
>         hlist_del(&clk->child_node);
>  
> -       if (new_parent)
> -               hlist_add_head(&clk->child_node, &new_parent->children);
> -       else
> -               hlist_add_head(&clk->child_node, &clk_orphan_list);
> +       hlist_add_head(&clk->child_node, &new_parent->children);

Rajagopal,

You found a bug, but not the right one :)

This change would result in never moving a clock into the orphan list if
the parent is missing.  The right thing to do is to allow the operation
to succeed and migrate this clock into the orphan list.  In keeping
with the clk.h api we need to treat struct clk new_parent as an opaque
cookie and not care whether or not it is NULL.

Untested patch below fixes the real bug:



>From a4d56e3ee51452366365749873710e16631e9de7 Mon Sep 17 00:00:00 2001
From: Mike Turquette <mturquette-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Date: Tue, 15 Jan 2013 14:39:06 -0800
Subject: [PATCH] clk: allow re-parenting to NULL clks

__clk_reparent presently bails early if the new parent of a clk is NULL.
This is wrong and prevents dynamically migrating clocks into the orphan
list.  The fix is to remove the NULL pointer check for new_parent in
__clk_parent.

Signed-off-by: Mike Turquette <mturquette-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 drivers/clk/clk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 593a2e4..f056230 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1186,7 +1186,7 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent)
 	struct dentry *new_parent_d;
 #endif
 
-	if (!clk || !new_parent)
+	if (!clk)
 		return;
 
 	hlist_del(&clk->child_node);
-- 
1.7.10.4