netdev - Re: [PATCH] isdn capi driver broken on 64 bit.

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Date:	Mon, 27 Aug 2007 09:16:55 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Karsten Keil <kkeil@...e.de>
Cc:	isdn4linux@...tserv.isdn4linux.de, netdev@...r.kernel.org
Subject: Re: [PATCH] isdn capi driver broken on 64 bit.

On Mon, 27 Aug 2007 13:02:26 +0200
Karsten Keil <kkeil@...e.de> wrote:

> On Fri, Aug 24, 2007 at 11:08:11AM -0700, Stephen Hemminger wrote:
> > The following driver API is broken on any architecture with 64 bit addresses.
> > because of cast that loses high bits.
> > 
> > Signed-off-by: Stephen Hemminger <shemminger@...ux-foundation.org>
> > 
> > 
> > --- a/drivers/isdn/capi/capidrv.c	2007-06-25 09:03:12.000000000 -0700
> > +++ b/drivers/isdn/capi/capidrv.c	2007-08-24 11:06:46.000000000 -0700
> > @@ -1855,6 +1855,9 @@ static int if_sendbuf(int id, int channe
> >  		return 0;
> >  	}
> >  	datahandle = nccip->datahandle;
> > +
> > +	/* This won't work on 64 bit! */
> > +	BUILD_BUG_ON(sizeof(skb->data) > sizeof(u32));
> >  	capi_fill_DATA_B3_REQ(&sendcmsg, global.ap.applid, card->msgid++,
> >  			      nccip->ncci,	/* adr */
> >  			      (u32) skb->data,	/* Data */
> 
> 
> NACK.
> 
> It is not a BUG.
> 
> This is OK, since this field must have a value and on 32 it has the correct
> one) On 64 bit this field is ignored (but also need a value, random data is
> bad as well).

If you are using it as a transaction ID, then you should generate one.
There is no guarantee that two skb's won't have the same 32 bit data value
on 64 bit.
-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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