From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754380AbcGZMCW (ORCPT ); Tue, 26 Jul 2016 08:02:22 -0400 Received: from mailout3.w1.samsung.com ([210.118.77.13]:60970 "EHLO mailout3.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752913AbcGZMCT (ORCPT ); Tue, 26 Jul 2016 08:02:19 -0400 X-AuditID: cbfec7f4-f796c6d000001486-b5-579751470c95 Subject: Re: [RFC PATCH 0/5] USB Audio Gadget refactoring To: Jassi Brar , Ruslan Bilovol References: <1464047440-20496-1-git-send-email-ruslan.bilovol@gmail.com> Cc: Clemens Ladisch , Felipe Balbi , Daniel Mack , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" From: Krzysztof Opasiak Message-id: <57975146.5090501@samsung.com> Date: Tue, 26 Jul 2016 14:02:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-version: 1.0 In-reply-to: Content-type: text/plain; charset=utf-8 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrKLMWRmVeSWpSXmKPExsVy+t/xq7rugdPDDe4cULA41vaE3WLJiYdM FtdWzGW3uLxrDpvFomWtzBY9O08wWnTOWM/kwO6xc9Zddo9NqzrZPH6s6Gf2+LxJLoAlissm JTUnsyy1SN8ugStj2qQFLAUz+Stm7D7P2sC4gKeLkZNDQsBE4sHdB0wQtpjEhXvr2boYuTiE BJYySly995sVJCEk8JxR4vCHUBBbWMBS4tnF6cwgtohAmMT2revYIRpmMEvc2zeTEcRhBmm4 tLgbKMPBwSagLzFvlyhIA6+AlsTJWTvAmlkEVCU+fJvICGKLCkRIzNr+gwmiRlDix+R7LCA2 p0CwxNejJ1lBxjALqEtMmZILEmYWkJfYvOYt8wRGgVlIOmYhVM1CUrWAkXkVo2hqaXJBcVJ6 rqFecWJucWleul5yfu4mRkhgf9nBuPiY1SFGAQ5GJR5ezpRp4UKsiWXFlbmHGCU4mJVEeCv9 p4cL8aYkVlalFuXHF5XmpBYfYpTmYFES5527632IkEB6YklqdmpqQWoRTJaJg1OqgVG7/bhM 1gHB7t28K7crvOWbKq32V05y6bu0eZL2OoveW2vrZmss+Hu8m2v9lv3OJY82fXsXsGKq8ka1 4vPrbzYFSG/csu7fafu6Nbv5nb/0CQQa39T992GDyAEtl4KMR0dOC3GtLp2gIaxlvPym24LQ XsX5E5hnerd6ZPyNFPg92aDrXuH6mbJKLMUZiYZazEXFiQD+tBe6aAIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/26/2016 10:53 AM, Jassi Brar wrote: > On Tue, Jul 26, 2016 at 7:01 AM, Ruslan Bilovol > wrote: >> On Fri, Jul 15, 2016 at 10:43 AM, Clemens Ladisch wrote: >>>>> On Tue, May 24, 2016 at 2:50 AM, Ruslan Bilovol >>>>> wrote: >>>>>> it may break current usecase for some people >>> >>> And what are the benefits that justify breaking the kernel API? >> >> >> Main limitation with current f_uac1 design is - it can be used only on systems >> with real ALSA card present and can have only exact number of >> channels / sampling rate as sink card has. >> Yet it is not flexible - can't do audio processing between f_uac1 and the card. >> Also if someone wants to bind f_uac1 it to another sound card he has to >> unload g_audio or reconfigure it through configfs - that means USB >> reenumeration on host device. >> >> If you have a "virtual sound card", audio processing is done in userspace >> and is more flexible. You even don't need to have a real sound card and >> can use some userspace application for playing/capturing audio samples. >> Moreover, existing f_uac2 (that is USB Audio Class 2.0 function >> implementation) already uses approach of "virtual sound card" >> > While I agree the virtual sound card approach is the right way, I am > not sure if we should break the userspace api that the existing UAC1 > driver exposes. Maybe we should add another virtual-sound-card > exposing UAC1 driver ... and hopefully very similar to (or just port > of) the f_audio_source.c from android. Definitely agree with this opinion. I don't see any benefits of breaking the API here instead of adding just another USB function. Maybe even some pieces of code could be shared with f_uac1.c but I think that this should be a brand new function. Best regards, -- Krzysztof Opasiak Samsung R&D Institute Poland Samsung Electronics