Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760245Ab0FRK33 (ORCPT ); Fri, 18 Jun 2010 06:29:29 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:52933 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759218Ab0FRK31 (ORCPT ); Fri, 18 Jun 2010 06:29:27 -0400 Subject: Re: [PATCH] ASoC: Fix overflow bug in SOC_DOUBLE_R_SX_TLV From: Liam Girdwood To: Stuart Longland Cc: ALSA Development List , Takashi Iwai , Mark Brown , Linux ARM Kernel , Linux Kernel In-Reply-To: <1276829770-31557-1-git-send-email-redhatter@gentoo.org> References: <20100618023810.GS7759@www.longlandclan.yi.org> <1276829770-31557-1-git-send-email-redhatter@gentoo.org> Content-Type: text/plain; charset="UTF-8" Date: Fri, 18 Jun 2010 11:29:24 +0100 Message-ID: <1276856964.3054.1.camel@odin> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1762 Lines: 44 On Fri, 2010-06-18 at 12:56 +1000, Stuart Longland wrote: > When SX_TLV widgets are read, if the gain is set to a value below 0dB, > the mixer control is erroniously read as being at maximum volume. > > The value read out of the CODEC register is never sign-extended, and > when the minimum value is subtracted (read; added, since the minimum is > negative) the result is a number greater than the maximum allowed value > for the control, and hence it saturates. > > Solution: Mask the result so that it "wraps around", emulating > sign-extension. > > Signed-off-by: Stuart Longland > --- > sound/soc/soc-core.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c > index a82a797..0470288 100644 > --- a/sound/soc/soc-core.c > +++ b/sound/soc/soc-core.c > @@ -2400,8 +2400,8 @@ int snd_soc_get_volsw_2r_sx(struct snd_kcontrol *kcontrol, > int val = snd_soc_read(codec, mc->reg) & mask; > int valr = snd_soc_read(codec, mc->rreg) & mask; > > - ucontrol->value.integer.value[0] = ((val & 0xff)-min); > - ucontrol->value.integer.value[1] = ((valr & 0xff)-min); > + ucontrol->value.integer.value[0] = ((val & 0xff)-min) & mask; > + ucontrol->value.integer.value[1] = ((valr & 0xff)-min) & mask; > return 0; > } > EXPORT_SYMBOL_GPL(snd_soc_get_volsw_2r_sx); Acked-by: Liam Girdwood -- Freelance Developer, SlimLogic Ltd ASoC and Voltage Regulator Maintainer. http://www.slimlogic.co.uk -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/