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Message-ID: <CAAP7uc+ytdWWDQU0eFozK1d=HkQ5YnvOqNbLQcjdy9qdJbgKYQ@mail.gmail.com>
Date: Wed, 4 Nov 2015 10:51:25 +0100
From: Aleksander Morgado <aleksander@...ksander.es>
To: Oliver Hartkopp <socketcan@...tkopp.net>
Cc: Marek Vasut <marex@...x.de>,
Vostrikov Andrey <andrey.vostrikov@...entembedded.com>,
Marc Kleine-Budde <mkl@...gutronix.de>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"David S. Miller" <davem@...emloft.net>,
Wolfgang Grandegger <wg@...ndegger.com>,
Andrew Lunn <andrew@...n.ch>
Subject: Re: [RFC][PATCH] net: arinc429: Add ARINC-429 stack
On Tue, Nov 3, 2015 at 6:01 PM, Oliver Hartkopp <socketcan@...tkopp.net> wrote:
>> Unrelated to all this, another key point in ARINC is the timing for
>> each label when transmitting. The common case you get is different
>> labels being sent continuously with a given rate for each. E.g. labels
>> 310 and 311 every 80ms, label 312 every 120ms and so on. I'm not sure
>> the HOLT chips have any specific way of configuring this, but I've
>> seen some USB devices which actually have APIs to say e.g. "send label
>> 310 every 80ms" and then you can just update the value being sent
>> without needing to take care of the TX rate. I'd have loved to see
>> that instead of the complex filtering :) I know this is way too much
>> for the generic kernel driver, though, so just a heads up of how this
>> usually works.
>>
>
> The CAN stack already has a solution for this.
>
> The CAN_BCM socket is a programmable (content) filter for cyclic messages
> which are common in automotive setups to detect timeouts in cyclic messages
> (sender fails).
>
> An the best thing: You can use the Linux internal high-res timers to send
> messages - just by creating a TX_SETUP configuration for the BCM.
>
> Read this:
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/Documentation/networking/can.txt?h=linux-4.2.y#n634
>
> Just one more reason to use PF_CAN :-)
This setup is actually very interesting for ARINC transmitters, indeed.
--
Aleksander
https://aleksander.es
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