From mboxrd@z Thu Jan 1 00:00:00 1970 From: Liam Girdwood Subject: Re: PATCH[1/1] Add I2S common driver for Intel MID platform Date: Wed, 20 Oct 2010 00:01:47 +0100 Message-ID: <1287529307.3272.579.camel@odin> References: <2A84145621092446B6659B8A0F28E26F46FE77084A@irsmsx501.ger.corp.intel.com> <20101019213212.GB29234@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-wy0-f179.google.com (mail-wy0-f179.google.com [74.125.82.179]) by alsa0.perex.cz (Postfix) with ESMTP id C8F5E244AC for ; Wed, 20 Oct 2010 01:01:47 +0200 (CEST) Received: by wyb32 with SMTP id 32so3145024wyb.38 for ; Tue, 19 Oct 2010 16:01:47 -0700 (PDT) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: pl bossart Cc: "alsa-devel@alsa-project.org" , Mark Brown , Peter Ujfalusi , "Le Gall, Louis" List-Id: alsa-devel@alsa-project.org On Tue, 2010-10-19 at 17:48 -0500, pl bossart wrote: > >> As this is used to transfer speech frames from/to cellular modem that have specific timing constraints (and modem also uses the I2S path to send some side-info), the Alsa SoC interface cannot be used. > > > > What makes you say this? You have provided no detail on what problems > > you believe exist and since ASoC is a *very* thin wrapper around the > > core ALSA for DMA stuff it is very surprising that you would see any > > issues here that don't also affect plain ALSA. If there are any issues > > then it would seem better to resolve these within the current framework > > rather than completely discarding the entire existing infrastructure. > > Louis meant ALSA rather than ASOC. We use burst transfers to reduce > round-trip delay, the whole notion of periods/period elapsed/ring > buffer doesn't make sense here and there is in-band signalling that > should not be interpreted as samples. If ALSA had a simplified API for > byte streams sent over a serial output, we would have no problems > using it and of course ASOC would be used then. Is the inband signaling here done in software ? I'd expect this to be multiplexed in the DAI by the hardware leaving the software to send PCM bursts to the CODEC/MODEM/whatever like Peter's DAC33 driver. Liam -- Freelance Developer, SlimLogic Ltd ASoC and Voltage Regulator Maintainer. http://www.slimlogic.co.uk