linux-kernel - Re: [very-RFC 7/8] AVB ALSA

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Date:	Wed, 15 Jun 2016 14:13:03 +0200
From:	Henrik Austad <henrik@...tad.us>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	alsa-devel@...r.kernel.org, netdev@...r.kernel.org,
	henrk@...tad.us, Henrik Austad <haustad@...co.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Takashi Iwai <tiwai@...e.de>, Mark Brown <broonie@...nel.org>
Subject: Re: [very-RFC 7/8] AVB ALSA - Add ALSA shim for TSN

On Wed, Jun 15, 2016 at 01:49:08PM +0200, Richard Cochran wrote:
> Now that I understand better...
> 
> On Sun, Jun 12, 2016 at 01:01:35AM +0200, Henrik Austad wrote:
> > Userspace is supposed to reserve bandwidth, find StreamID etc.
> > 
> > To use as a Talker:
> > 
> > mkdir /config/tsn/test/eth0/talker
> > cd /config/tsn/test/eth0/talker
> > echo 65535 > buffer_size
> > echo 08:00:27:08:9f:c3 > remote_mac
> > echo 42 > stream_id
> > echo alsa > enabled
> 
> This is exactly why configfs is the wrong interface.  If you implement
> the AVB device in alsa-lib user space, then you can handle the
> reservations, configuration, UDP sockets, etc, in a way transparent to
> the aplay program.

And how would v4l2 benefit from this being in alsalib? Should we require 
both V4L and ALSA to implement the same, or should we place it in a common 
place for all.

And what about those systems that want to use TSN but is not a 
media-device, they should be given a raw-socket to send traffic over, 
should they also implement something in a library?

So no, here I think configfs is an apt choice.

> Heck, if done properly, your layer could discover the AVB nodes in the
> network and present each one as a separate device...

No, you definately do not want the kernel to automagically add devices 
whenever something pops up on the network, for this you need userspace to 
be in control. 1722.1 should not be handled in-kernel.


-- 
Henrik Austad

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