linux-kernel - Re: [PATCH 12/12] [RFC] can: avoid using timeval for uapi

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Message-ID: <7548522.iLToS4O3HD@wuerfel>
Date:	Tue, 06 Oct 2015 10:32:58 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Oliver Hartkopp <socketcan@...tkopp.net>
Cc:	netdev@...r.kernel.org, y2038@...ts.linaro.org,
	linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	linux-can@...r.kernel.org, linux-api@...r.kernel.org
Subject: Re: [PATCH 12/12] [RFC] can: avoid using timeval for uapi

On Monday 05 October 2015 20:51:08 Oliver Hartkopp wrote:
> 
> I double checked some (more) BCM applications I have access to.
> 
> E.g. https://github.com/linux-can/can-tests
> 
> When you do a 'git grep ival1' there you get something like
> 
> tst-bcm-cycle.c:        msg.msg_head.ival1.tv_sec = 1;
> tst-bcm-cycle.c:        msg.msg_head.ival1.tv_usec = 0;
> tst-bcm-cycle.c:        msg.msg_head.ival1.tv_sec = 0;
> tst-bcm-cycle.c:        msg.msg_head.ival1.tv_usec = 0;
> tst-bcm-dump.c: msg.msg_head.ival1.tv_sec       = timeout / 1000000;
> tst-bcm-dump.c: msg.msg_head.ival1.tv_usec      = timeout % 1000000;
> (..)
> 
> So the usual way to assign values to ival1 and ival2 is NOT to assign an
> existing struct timeval but to directly assign its tv_[u]sec elements.

Ok, very good.

> I applied your bcm.h changes to my local can-tests tree and it compiles
> without any problems - as expected. I don't see any serious drawback with your
> idea. I wonder whether developers would ever notice this change ...
> 
> > We could address problem a) by using '__u32' or 'int' members
> > rather than 'long', but that would have a more significant
> > downside in also breaking support for all existing 64-bit user
> > binaries that might be using this interface, which is likely
> > not acceptable.
> 
> Indeed.
> 
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > Cc: Oliver Hartkopp <socketcan@...tkopp.net>
> 
> Thanks for your good suggestion to make the BCM API y2038 proof!
> 
> Acked-by: Oliver Hartkopp <socketcan@...tkopp.net>

Thanks.

What is the normal path for CAN patches? Should I resend with your
Ack and without the RFC for Marc to pick it up?

	Arnd
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