linux-kernel - Re: [PATCH] mtd: ichxrom: maybe-uninitialized with gcc-4.9

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Date:   Mon, 24 Oct 2016 22:47:59 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     Arnd Bergmann <arnd@...db.de>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>
Cc:     Julia Lawall <julia.lawall@...6.fr>, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mtd: ichxrom: maybe-uninitialized with gcc-4.9

On 10/24/2016 05:28 PM, Arnd Bergmann wrote:
> pci_read_config_word() might fail and not initialize its output,
> as pointed out by older versions of gcc when using the -Wmaybe-unintialized
> flag:
> 
> drivers/mtd/maps/ichxrom.c: In function ‘ichxrom_cleanup’:
> drivers/mtd/maps/ichxrom.c:63:2: error: ‘word’ is used uninitialized in this function [-Werror=uninitialized]
> 
> This is apparently a correct warning, though it does not show up
> with newer compilers. Changing the code to not attempt to write
> back uninitialized data into PCI config space is a correct
> fix for the problem and avoids the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Marek Vasut <marex@...x.de>

> ---
>  drivers/mtd/maps/ichxrom.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/maps/ichxrom.c b/drivers/mtd/maps/ichxrom.c
> index e17d02ae03f0..976d42f63aef 100644
> --- a/drivers/mtd/maps/ichxrom.c
> +++ b/drivers/mtd/maps/ichxrom.c
> @@ -57,10 +57,12 @@ static void ichxrom_cleanup(struct ichxrom_window *window)
>  {
>  	struct ichxrom_map_info *map, *scratch;
>  	u16 word;
> +	int ret;
>  
>  	/* Disable writes through the rom window */
> -	pci_read_config_word(window->pdev, BIOS_CNTL, &word);
> -	pci_write_config_word(window->pdev, BIOS_CNTL, word & ~1);
> +	ret = pci_read_config_word(window->pdev, BIOS_CNTL, &word);
> +	if (!ret)
> +		pci_write_config_word(window->pdev, BIOS_CNTL, word & ~1);
>  	pci_dev_put(window->pdev);
>  
>  	/* Free all of the mtd devices */
> 


-- 
Best regards,
Marek Vasut