From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752994Ab3BUJDj (ORCPT ); Thu, 21 Feb 2013 04:03:39 -0500 Received: from cantor2.suse.de ([195.135.220.15]:57203 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752713Ab3BUJDh (ORCPT ); Thu, 21 Feb 2013 04:03:37 -0500 Date: Thu, 21 Feb 2013 10:03:34 +0100 Message-ID: From: Takashi Iwai To: Pawel Moll Cc: Jaroslav Kysela , Daniel Mack , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ALSA: usb: Fix Processing Unit Descriptor parsers In-Reply-To: <1361411750-30056-1-git-send-email-mail@pawelmoll.com> References: <1361411750-30056-1-git-send-email-mail@pawelmoll.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.2 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At Thu, 21 Feb 2013 01:55:50 +0000, Pawel Moll wrote: > > Commit 99fc86450c439039d2ef88d06b222fd51a779176 "ALSA: usb-mixer: > parse descriptors with structs" introduced a set of useful parsers > for descriptors. Unfortunately the parses for the Processing Unit > Descriptor came with a very subtle bug... > > Functions uac_processing_unit_iProcessing() and > uac_processing_unit_specific() were indexing the baSourceID array > forgetting the fields before the iProcessing and process-specific > descriptors. > > The problem was observed with Sound Blaster Extigy mixer, > where nNrModes in Up/Down-mix Processing Unit Descriptor > was accessed at offset 10 of the descriptor (value 0) > instead of offset 15 (value 7). In result the resulting > control had interesting limit values: > > Simple mixer control 'Channel Routing Mode Select',0 > Capabilities: volume volume-joined penum > Playback channels: Mono > Capture channels: Mono > Limits: 0 - -1 > Mono: -1 [100%] > > Fixed by starting from the bmControls, which was calculated > correctly, instead of baSourceID. > > Now the mentioned control is fine: > > Simple mixer control 'Channel Routing Mode Select',0 > Capabilities: volume volume-joined penum > Playback channels: Mono > Capture channels: Mono > Limits: 0 - 6 > Mono: 0 [0%] > > Signed-off-by: Pawel Moll > --- > include/uapi/linux/usb/audio.h | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/include/uapi/linux/usb/audio.h b/include/uapi/linux/usb/audio.h > index ac90037..d2314be 100644 > --- a/include/uapi/linux/usb/audio.h > +++ b/include/uapi/linux/usb/audio.h > @@ -384,14 +384,16 @@ static inline __u8 uac_processing_unit_iProcessing(struct uac_processing_unit_de > int protocol) > { > __u8 control_size = uac_processing_unit_bControlSize(desc, protocol); > - return desc->baSourceID[desc->bNrInPins + control_size]; > + return *(uac_processing_unit_bmControls(desc, protocol) > + + control_size); > } > > static inline __u8 *uac_processing_unit_specific(struct uac_processing_unit_descriptor *desc, > int protocol) > { > __u8 control_size = uac_processing_unit_bControlSize(desc, protocol); > - return &desc->baSourceID[desc->bNrInPins + control_size + 1]; > + return uac_processing_unit_bmControls(desc, protocol) > + + control_size + 1; > } Looks good to me. An alternative would be to change uac_processing_unit_bControlSize() to correct the header size, but I don't think it's good, as bControlSize fields in other units show the value including the header size. Daniel, what do you think? thanks, Takashi