linux-kernel - Re: [very-RFC 0/8] TSN driver for the kernel

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Date:	Tue, 14 Jun 2016 12:18:44 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	Henrik Austad <henrik@...tad.us>, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, alsa-devel@...r.kernel.org,
	netdev@...r.kernel.org, henrk@...tad.us,
	Arnd Bergmann <arnd@...aro.org>
Subject: Re: [very-RFC 0/8] TSN driver for the kernel

On Mon, 13 Jun 2016 21:51:36 +0200
Richard Cochran <richardcochran@...il.com> wrote:

> On Mon, Jun 13, 2016 at 01:47:13PM +0200, Richard Cochran wrote:
> > 3. ALSA support for tunable AD/DA clocks.  The rate of the Listener's
> >    DA clock must match that of the Talker and the other Listeners.
> >    Either you adjust it in HW using a VCO or similar, or you do
> >    adaptive sample rate conversion in the application. (And that is
> >    another reason for *not* having a shared kernel buffer.)  For the
> >    Talker, either you adjust the AD clock to match the PTP time, or
> >    you measure the frequency offset.  
> 
> Actually, we already have support for tunable clock-like HW elements,
> namely the dynamic posix clock API.  It is trivial to write a driver
> for VCO or the like.  I am just not too familiar with the latest high
> end audio devices.

Why high end ? Even the most basic USB audio is frame based and
isosynchronous to the USB clock. It also reports back the delay
properties.

Alan