linux-kernel - Re: [alsa-devel] [PATCH] ASoC: soc-pcm: Use delay set in pointer function

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Date:   Tue, 31 Jul 2018 12:32:59 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Mark Brown <broonie@...nel.org>
Cc:     "Agrawal, Akshu" <Akshu.Agrawal@....com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        "moderated list:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM..." 
        <alsa-devel@...a-project.org>, Alexander.Deucher@....com,
        djkurtz@...omium.org, Liam Girdwood <lgirdwood@...il.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [alsa-devel] [PATCH] ASoC: soc-pcm: Use delay set in pointer function

On Tue, 31 Jul 2018 12:19:43 +0200,
Mark Brown wrote:
> 
> On Tue, Jul 31, 2018 at 11:25:11AM +0200, Takashi Iwai wrote:
> 
> > It's not necessary that all CPU dais provide the pointer callback.
> > My suggestion is that, if CPU dai *wants* to provide the base delay,
> > it must be tied with the position value, hence it should provide the
> > pointer callback.  If CPU dai has a pointer callback,
> > snd_soc_pcm_pointer() skips the component pointer callback but uses
> > CPU dai pointer callback instead.
> 
> However since it's not supposed to be providing any DMA a CPU DAI really
> shouldn't be doing this...

Well, if so, the CPU dai also cannot get the exact base delay
corresponding to the reported position, either, no?


Takashi