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Date: Fri, 21 Mar 2003 11:21:08 +0100
From: Pavel Machek <pavel@suse.cz>
To: Andi Kleen <ak@suse.de>
Cc: "David S. Miller" <davem@redhat.com>, linux-kernel@vger.kernel.org,
       torvalds@transmeta.com
Subject: Re: share COMPATIBLE_IOCTL()s across architectures
Message-ID: <20030321102108.GA2458@atrey.karlin.mff.cuni.cz>
References: <20030319232157.GA13415@elf.ucw.cz> <20030319.160130.112180221.davem@redhat.com> <20030320193212.GA312@elf.ucw.cz> <1048191889.15338.189.camel@averell>
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Hi!

> > >    This patche moves common COMPATIBLE_IOCTLs to
> > >    include/linux/compat_ioctl.h, enabling pretty nice cleanups:
> > > 
> > > Please be careful.  For anything non-trivial there can be major
> > > differences between compat layers.
> > 
> > I'm trying to be carefull. How common are ioctls that are
> > COMPATIBLE_IOCTL(foo) on one arch, but not on another? So far I tried
> > to decide, and mostly decided that one architecture was simply
> > missing...
> 
> The only issue I'm aware of are structures with long long. IA64 and
> x86-64 are special in that long long has a different alignmnet in 32bit
> and 64bit (4 bytes in 32bit, 8 bytes in 64bit). All the other archs with
> compat code have always 8 byte alignment. This means if sparc64 doesn't
> do a conversion, but x86-64 does you cannot put it into the COMPAT_IOCTL
> list. Make sure you only use the common set.
> 
> Fortunately long long is not that common and many uses of it are already
> 8 byte aligned, but not all are.

Okay, I was carefull this time to only include common set. (I still
think that most differences are simple bugs).

									Pavel
-- 
Horseback riding is like software...
...vgf orggre jura vgf serr.
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