From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH] ASoC: kirkwood: add S/PDIF support Date: Fri, 18 Oct 2013 15:27:40 +0100 Message-ID: <20131018142740.GY25034@n2100.arm.linux.org.uk> References: <20130924124122.64834b2a@armhf> <20131018003439.GG2443@sirena.org.uk> <20131018103019.GW25034@n2100.arm.linux.org.uk> <20131018124832.GK2443@sirena.org.uk> <20131018125638.GX25034@n2100.arm.linux.org.uk> <20131018134829.GQ2443@sirena.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20131018134829.GQ2443-GFdadSzt00ze9xe1eoZjHA@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mark Brown Cc: Jean-Francois Moine , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, alsa-devel-K7yf7f+aM1XWsZ/bQMPhNw@public.gmane.org, Takashi Iwai , Liam Girdwood , Rob Herring , Jaroslav Kysela , Grant Likely , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org On Fri, Oct 18, 2013 at 02:48:29PM +0100, Mark Brown wrote: > On Fri, Oct 18, 2013 at 01:56:38PM +0100, Russell King - ARM Linux wrote: > > > Let me remind you that I had a definition of what a front end and a back > > end DAI was from Liam, and your definition is at odds with that. > > Could you please provide some detail on this? I was aware that you were > for a time confused about this but had not been aware of the source of > the confusion. Let's see: 16:10 < rmk> broonie: can you explain this pcm frontend/backend stuff in asoc. what exactly is a frontend and backend pcm, and how do they relate to the CPU hardware and codec links? Which are the ones which are given ALSA PCMs? 17:22 < broonie> rmk: A front end is the bit that does DMA from memory, a back end is a physical interface. 17:22 < broonie> The bit in the middle is usually a DSP. 17:23 < broonie> To be frank I've not actually *used* this stuff myself except in bolting a new CODEC on the edge of it during system integrations - going to be rectifying that very soon with the Samsung drivers I hope. 17:24 < broonie> But the general idea is that the front end is what the application sees, the back end is what comes out of the hardware at the other end. 17:25 < broonie> And the bit in the middle does any routing an rewriting of formats between the two. 17:26 < broonie> (The Samsung picture should be very similar to Kirkwood but the opposite way around - two front ends mixed togther to a single back end) ... 16:49 < rmk> oh, another question 16:49 < rmk> .dynamic in the dai link structure, that's for backends only, right? 16:50 < broonie> Think so, yes. 16:52 < rmk> hmm 16:52 < rmk> if (rtd->dai_link->dynamic) { 16:52 < rmk> rtd->ops.open = dpcm_fe_dai_open; 16:52 < rmk> probably needed for frontends -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html