From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:41888 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750842Ab2FKIFP (ORCPT ); Mon, 11 Jun 2012 04:05:15 -0400 From: Laurent Pinchart To: Ezequiel Garcia Cc: linux-media , Hans Verkuil , Mauro Carvalho Chehab Subject: Re: [Q] Why is it needed to add an alsa module to v4l audio capture devices? Date: Mon, 11 Jun 2012 10:05:20 +0200 Message-ID: <2041118.ct8h3d9SmG@avalon> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Ezequiel, On Thursday 07 June 2012 15:26:04 Ezequiel Garcia wrote: > Hi all, > > (I hope this is a genuine question, and I'm not avoiding my own homework > here.) > > I'm trying to support the audio part of the stk1160 usb bridge (similar to > em28xx). Currently, the snd-usb-audio module is being loaded when I > physically plug my device, but I can't seem to capture any sound with vlc. > > I still have to research and work a lot to understand the connection between > my device and alsa, and altough I could write a working module similar to > em28xx-alsa.ko, I still can't figure out why do I need to write one in the > first place. > > Why is this module suffficient for gspca microphone devices (gspca, to name > one) and why is a new alsa driver needed for em28xx (or stk1160)? Some devices expose audio functionality by implementing the UAC (USB Audio Class) specification. The snd-usb-audio module is all you should need for those devices. Other vendors support audio by using their own proprietary protocol. In those cases you will need a device-specific kernel module. -- Regards, Laurent Pinchart