Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751567AbaAMK5G (ORCPT ); Mon, 13 Jan 2014 05:57:06 -0500 Received: from cantor2.suse.de ([195.135.220.15]:57744 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750730AbaAMK5E (ORCPT ); Mon, 13 Jan 2014 05:57:04 -0500 Date: Mon, 13 Jan 2014 11:57:02 +0100 Message-ID: From: Takashi Iwai To: Liam Girdwood Cc: "alsa-devel@alsa-project.org" , Mark Brown , "linux-kernel@vger.kernel.org" , Nenghua Cao Subject: Re: [alsa-devel] [PATCH] ASoC: dpcm: don't do hw_param when BE has done hw_param In-Reply-To: <1389610131.2326.16.camel@loki> References: <1389332195-15900-1-git-send-email-nhcao@marvell.com> <52CFD7BE.5030907@marvell.com> <1389354435.2293.32.camel@loki> <52CFE0AE.1030606@marvell.com> <1389356948.2293.55.camel@loki> <1389379389.2293.114.camel@loki> <1389610131.2326.16.camel@loki> 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/24.3 (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 Mon, 13 Jan 2014 10:48:51 +0000, Liam Girdwood wrote: > > On Sat, 2014-01-11 at 10:35 +0100, Takashi Iwai wrote: > > At Fri, 10 Jan 2014 18:43:09 +0000, > > Liam Girdwood wrote: > > > > > > On Fri, 2014-01-10 at 14:46 +0100, Takashi Iwai wrote: > > > > At Fri, 10 Jan 2014 12:29:08 +0000, > > > > Liam Girdwood wrote: > > > > > > > > > > > > The intention was to use the existing alsa-lib/tinyalsa PCM hw_params > > > APIs. The BE would just export itself to usespace as a PCM (but without > > > the capability for direct playback/capture - just format, rate setting) > > > > Does it mean that, from kernel perspective, a BE creates a dedicated > > (virtual) PCM device and expose it to user-space? Or just through > > special API? > > I'm thinking a virtual PCM if you agree. > > We could keep the same userspace API for configuration OR we could > extend the API slightly to add some snd_pcm_virtual_() functions. > Extending the API would imply the virtual PCM only supports a subset of > PCM API calls (avoiding any confusion/mixing with regular PCM APIs). Yeah, I agree that a simple PCM device exposure would be more straightforward. thanks, Takashi -- 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/