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

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Date:   Mon, 24 Oct 2016 17:28:35 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>, Julia Lawall <julia.lawall@...6.fr>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [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@...db.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