From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Subject: Re: [RFC][PATCH] net: arinc429: Add ARINC-429 stack Date: Tue, 10 Nov 2015 17:15:39 +0100 Message-ID: <201511101715.39253.marex@denx.de> References: <1446419775-5215-1-git-send-email-marex@denx.de> <201511041633.33504.marex@denx.de> Mime-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Vostrikov Andrey , Oliver Hartkopp , "Marc Kleine-Budde" , "netdev@vger.kernel.org" , "David S. Miller" , Wolfgang Grandegger , Andrew Lunn To: Aleksander Morgado Return-path: Received: from mail-out.m-online.net ([212.18.0.10]:46405 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752872AbbKJQQZ (ORCPT ); Tue, 10 Nov 2015 11:16:25 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Wednesday, November 04, 2015 at 04:45:20 PM, Aleksander Morgado wrote: > On Wed, Nov 4, 2015 at 4:33 PM, Marek Vasut 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 > >> > >> 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? Sorry for being so late into the discussion. I got confused by hi-3585_v-rev-l.pdf page 7 right, CR4 lets you treat bit 32 as either data or parity. But I guess this is not the general case. So I wonder, does it make sense to treat the P bit as data always and do parity in software or not ? Best regards, Marek Vasut