From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967455AbcA1LQE (ORCPT ); Thu, 28 Jan 2016 06:16:04 -0500 Received: from mail-wm0-f41.google.com ([74.125.82.41]:38279 "EHLO mail-wm0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967310AbcA1LP6 (ORCPT ); Thu, 28 Jan 2016 06:15:58 -0500 Date: Thu, 28 Jan 2016 11:15:53 +0000 From: Lee Jones To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, Linus Walleij , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mfd: db8500: avoid uninitialized variable reference Message-ID: <20160128111553.GN3368@x1> References: <1453737752-1960326-1-git-send-email-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1453737752-1960326-1-git-send-email-arnd@arndb.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 25 Jan 2016, Arnd Bergmann wrote: > The prcmu_config_clkout() function ensures that the 'clkout' argument > can only be '0' or '1' using an appropriate BUG_ON(), so the compiler > should know that the div_mask, mask, and bits variables are always > initialized later on. However, it doesn't understand this in gcc-5.2 > and produces a false positive warning instead: > > drivers/mfd/db8500-prcmu.c: In function 'prcmu_config_clkout': > drivers/mfd/db8500-prcmu.c:762:10: error: 'div_mask' may be used uninitialized in this function [-Werror=maybe-uninitialized] > if (val & div_mask) { > ^ > drivers/mfd/db8500-prcmu.c:769:13: error: 'mask' may be used uninitialized in this function [-Werror=maybe-uninitialized] > if ((val & mask & ~div_mask) != bits) { > ^ > drivers/mfd/db8500-prcmu.c:757:7: error: 'bits' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > Replacing the switch() statement with an equivalent if() lets > gcc figure this out reliably and avoids the warnings. > > Signed-off-by: Arnd Bergmann > --- > drivers/mfd/db8500-prcmu.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) Applied, thanks. > diff --git a/drivers/mfd/db8500-prcmu.c b/drivers/mfd/db8500-prcmu.c > index 12099b09a9a7..c0a86aeb1733 100644 > --- a/drivers/mfd/db8500-prcmu.c > +++ b/drivers/mfd/db8500-prcmu.c > @@ -739,20 +739,17 @@ int prcmu_config_clkout(u8 clkout, u8 source, u8 div) > if (!div && !requests[clkout]) > return -EINVAL; > > - switch (clkout) { > - case 0: > + if (clkout == 0) { > div_mask = PRCM_CLKOCR_CLKODIV0_MASK; > mask = (PRCM_CLKOCR_CLKODIV0_MASK | PRCM_CLKOCR_CLKOSEL0_MASK); > bits = ((source << PRCM_CLKOCR_CLKOSEL0_SHIFT) | > (div << PRCM_CLKOCR_CLKODIV0_SHIFT)); > - break; > - case 1: > + } else { > div_mask = PRCM_CLKOCR_CLKODIV1_MASK; > mask = (PRCM_CLKOCR_CLKODIV1_MASK | PRCM_CLKOCR_CLKOSEL1_MASK | > PRCM_CLKOCR_CLK1TYPE); > bits = ((source << PRCM_CLKOCR_CLKOSEL1_SHIFT) | > (div << PRCM_CLKOCR_CLKODIV1_SHIFT)); > - break; > } > bits &= mask; > -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog