netdev - Re: [RFC][PATCH] net: arinc429: Add ARINC-429 stack

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Message-ID: <CAAP7ucJZxqUdA-B4m=u-+-BGkydYaSdnutiPf4ik36EcfjiUzQ@mail.gmail.com>
Date:	Wed, 4 Nov 2015 16:45:20 +0100
From:	Aleksander Morgado <aleksander@...ksander.es>
To:	Marek Vasut <marex@...x.de>
Cc:	Vostrikov Andrey <andrey.vostrikov@...entembedded.com>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	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 Wed, Nov 4, 2015 at 4:33 PM, Marek Vasut <marex@...x.de> wrote:
> On Wednesday, November 04, 2015 at 04:19:45 PM, Aleksander Morgado wrote:
>> On Wed, Nov 4, 2015 at 4:18 PM, Vostrikov Andrey
>>
>> <andrey.vostrikov@...entembedded.com> wrote:
>> >>> > About the parity -- can we add some flag into the datagram to
>> >>> > indicate we want hardware to calculate the parity for that
>> >>> > particular datagram for us? And we'd also need to indicate what type
>> >>> > of parity. I dunno if this is worth the hassle.
>> >>>
>> >>> This  is HW configuration property, it does not belong to  datagram.
>> >>> Also for TX channels,  parity could  be  two  kinds:  odd and even,
>> >>> for RX it is only on/off.
>> >>
>> >> There are datagrams which do contain parity and ones which do not
>> >> contain it, correct ? Thus, it's a property of that particular
>> >> datagram.
>>
>> All ARINC words have bit #31 as parity bit; whether it's used or not
>> depends on the setup as Andrey says below.
>
> Can bit 31 be ever used for DATA instead of parity ? Or is this just me
> not understanding the parlance of the specification, where "DATA" actually
> means "DATA with parity" ?

Well, as far as I know bit 31 is always parity bit, never used for
actual data contents. Which is the spec section that got you confused?
Maybe I'm the one which didn't read it well?

-- 
Aleksander
https://aleksander.es
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