Re: [Jack-Devel] Jack-Devel Digest, Vol 56, Issue 47

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DateSat, 26 Feb 2011 13:43:41 +0100
From Adrian Knoth <[hidden] at drcomp dot erfurt dot thur dot de>
To[hidden] at lists dot jackaudio dot org
In-Reply-ToChristoph Kuhr Re: [Jack-Devel] Jack-Devel Digest, Vol 56, Issue 47
Follow-UpArnold Krille Re: [Jack-Devel] Jack-Devel Digest, Vol 56, Issue 47
On Sat, Feb 26, 2011 at 09:41:52AM +0100, Christoph Kuhr wrote:

> since there is the PTPv2 sw implementation  
> (http://www.bartky.net/products.htm), the endpoint requirements of avb  
> are met by most computer hardware, but requires extensive network kernel  
> module modification.

Hmm, not sure if I entirely understand what you mean here, but last time
I had a look at PTP, I found at least three different versions with
different features.

To my knowledge, there are only thee NICs available which make sense to
be used with PTP: some embedded blackfin, gianfar and the Intel 82576
chips. All those support hardware timestamping, and support for it is
already in the kernel (since 2.6.32, iirc)

The ioctl in question is SIOCSHWTSTAMP, see
Documentation/networking/timestamping.txt in the Linux kernel.

IIRC, there is PTPv1 with SIOCSHWTSTAMP support and no PTPv2-HW except
the bartky freescale thing, but that's tailored to a special embedded
device and not using the common ioctl.

Given that there is no clear PTP upstream, one should first start to
merge all these three implementations and mabye forward-port the
SIOCSHWTSTAMP implementation from PTPv1 to PTPv2 or modify bartky's
v2-implementation to SIOCSHWTSTAMP (given that bartky is using a sane
license, haven't checked that)


So to me, I don't see the need for extensive network kernel module
modifcations, because everything is either already there or won't work
at all, because HW-timestamping needs to be supported physically in the
NIC, and there are only three (grep -R for SIOCSHWTSTAMP in
drivers/net).


I'm also touching this field a bit at the moment, so if you like, it
might make sense to coordinate our work, maybe even with Arnold and/or
Florian who has probably the most experience in this area.


I'll hopefully get my Intel NICs in early March, so I can provide you
with a remote login if you want to work with PTPv2 capable hardware.



Cheers

-- 
mail: [hidden]  	http://adi.thur.de	PGP/GPG: key via keyserver
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