linux-kernel - Re: [PATCH] clk: vt8500: don't return possibly uninitialized data

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Date:	Mon, 1 Feb 2016 17:15:45 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Michael Turquette <mturquette@...libre.com>,
	linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andrzej Hajda <a.hajda@...sung.com>,
	linux-arm-kernel@...ts.infradead.org,
	Tony Prisk <linux@...sktech.co.nz>,
	Roman Volkov <v1ron@...l.ru>
Subject: Re: [PATCH] clk: vt8500: don't return possibly uninitialized data

On 02/01, Arnd Bergmann wrote:
> The clk-vt8500.c driver would previously enter an endless loop
> when invalid settings got requested, this was now fixed. However,
> the driver will now return uninitialized data for a subset of those
> cases instead, as the gcc correctly warns:
> 
> clk/clk-vt8500.c: In function 'wm8650_find_pll_bits':
> clk/clk-vt8500.c:423:12: error: 'best_div2' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>   *divisor2 = best_div2;
>             ^
> clk/clk-vt8500.c:422:12: error: 'best_div1' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>   *divisor1 = best_div1;
>             ^
> clk/clk-vt8500.c:421:14: error: 'best_mul' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>   *multiplier = best_mul;
> 
> This reworks the error handling in the driver so we now return
> -EINVAL from clk_round_rate() and clk_set_rate() when we get
> impossible inputs.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Fixes: 090341b0a95d ("clk: vt8500: fix sign of possible PLL values")

My compiler still gets warnings even after this patch is applied.

drivers/clk/clk-vt8500.c: In function ‘wm8750_find_pll_bits’:
drivers/clk/clk-vt8500.c:509:12: warning: ‘best_div2’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c:508:12: warning: ‘best_div1’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c:507:14: warning: ‘best_mul’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c: In function ‘wm8650_find_pll_bits’:
drivers/clk/clk-vt8500.c:430:12: warning: ‘best_div2’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c:429:12: warning: ‘best_div1’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c:428:14: warning: ‘best_mul’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c: In function ‘wm8850_find_pll_bits’:
drivers/clk/clk-vt8500.c:560:12: warning: ‘best_div2’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c:559:12: warning: ‘best_div1’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/clk/clk-vt8500.c:558:14: warning: ‘best_mul’ may be used uninitialized in this function [-Wmaybe-uninitialized]

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