linux-kernel - [PATCH] clk: fix false-positive Wmaybe-uninitialized warning

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Message-Id: <20180216152807.1629038-1-arnd@arndb.de>
Date:   Fri, 16 Feb 2018 16:27:47 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>
Cc:     Arnd Bergmann <arnd@...db.de>, stable@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>,
        linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] clk: fix false-positive Wmaybe-uninitialized warning

When we build this driver with on x86-32, gcc produces a false-positive warning:

drivers/clk/renesas/clk-sh73a0.c: In function 'sh73a0_cpg_clocks_init':
drivers/clk/renesas/clk-sh73a0.c:155:10: error: 'parent_name' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   return clk_register_fixed_factor(NULL, name, parent_name, 0,

We can work around that warning by adding a fake initialization, I tried
and failed to come up with any better workaround. This is currently one
of few remaining warnings for a 4.14.y randconfig build, so it would be
good to also have it backported at least to that version. Older versions
have more randconfig warnings, so we might not care.

I had not noticed this earlier, because one patch in my randconfig test
tree removes the '-ffreestanding' option on x86-32, and that avoids
the warning. The -ffreestanding flag was originally global but moved
into arch/i386 by Andi Kleen in commit 6edfba1b33c7 ("[PATCH] x86_64:
Don't define string functions to builtin") as a 'temporary workaround'.

Like many temporary hacks, this turned out to be rather long-lived, from
all I can tell we still need a simple fix to asm/string_32.h before it
can be removed, but I'm not sure about how to best do that.

Cc: stable@...r.kernel.org
Cc: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/clk/renesas/clk-sh73a0.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/renesas/clk-sh73a0.c b/drivers/clk/renesas/clk-sh73a0.c
index eea38f6ea77e..3892346c4fcc 100644
--- a/drivers/clk/renesas/clk-sh73a0.c
+++ b/drivers/clk/renesas/clk-sh73a0.c
@@ -46,7 +46,7 @@ struct div4_clk {
 	unsigned int shift;
 };

-static struct div4_clk div4_clks[] = {
+static const struct div4_clk div4_clks[] = {
 	{ "zg", "pll0", CPG_FRQCRA, 16 },
 	{ "m3", "pll1", CPG_FRQCRA, 12 },
 	{ "b",  "pll1", CPG_FRQCRA,  8 },
@@ -79,7 +79,7 @@ sh73a0_cpg_register_clock(struct device_node *np, struct sh73a0_cpg *cpg,
 {
 	const struct clk_div_table *table = NULL;
 	unsigned int shift, reg, width;
-	const char *parent_name;
+	const char *parent_name = NULL;
 	unsigned int mult = 1;
 	unsigned int div = 1;

@@ -135,7 +135,7 @@ sh73a0_cpg_register_clock(struct device_node *np, struct sh73a0_cpg *cpg,
 		shift = 24;
 		width = 5;
 	} else {
-		struct div4_clk *c;
+		const struct div4_clk *c;

 		for (c = div4_clks; c->name; c++) {
 			if (!strcmp(name, c->name)) {
-- 
2.9.0