From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [alsa-devel] [PATCH] ASoC: dpcm: don't do hw_param when BE has done hw_param Date: Mon, 13 Jan 2014 11:57:02 +0100 Message-ID: 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> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <1389610131.2326.16.camel@loki> Sender: linux-kernel-owner@vger.kernel.org To: Liam Girdwood Cc: "alsa-devel@alsa-project.org" , Mark Brown , "linux-kernel@vger.kernel.org" , Nenghua Cao List-Id: alsa-devel@alsa-project.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