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

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  [PATCH] mtd: ichxrom: maybe-uninitialized with gcc-4.9 Arnd Bergmann <arnd@arndb.de> - 2016-10-24 17:30 +0200
    Re: [PATCH] mtd: ichxrom: maybe-uninitialized with gcc-4.9 Marek Vasut <marek.vasut@gmail.com> - 2016-10-24 22:50 +0200

#1507303 — [PATCH] mtd: ichxrom: maybe-uninitialized with gcc-4.9

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@arndb.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 */
-- 
2.9.0

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#1507717

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@arndb.de>

Reviewed-by: Marek Vasut <marex@denx.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

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