linux-kernel - Re: [PATCH] x86 byteorder.h: use __asm__/__inline_

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Message-ID: <495693E5.3060604@zytor.com>
Date:	Sat, 27 Dec 2008 12:45:25 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mike Frysinger <vapier@...too.org>
CC:	Sam Ravnborg <sam@...nborg.org>, Ingo Molnar <mingo@...e.hu>,
	tglx@...utronix.de, mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86 byteorder.h: use __asm__/__inline__ for userspace

Mike Frysinger wrote:
> On Saturday 27 December 2008 14:23:19 H. Peter Anvin wrote:
>> Mike Frysinger wrote:
>>> {su}{8,16,32,64} doesnt matter too much to me vs {u,}int_t{8,16,32,64}_t.
>>>  as long as people stop using __{su}{8,16,32,64}.  using the latter
>>> though does mean headers will more likely be "just usable" w/out needing
>>> linux/types.h include.  but then people would be forced to include
>>> stdint.h or similar before a linux header ... and that sucks.
>> That is a total non-starter.  This would mean that the C library itself
>> cannot use these headers without exporting additional symbols into the
>> namespace, *WHICH IT IS NOT ALLOWED TO DO*.
> 
> which is already happening today you mean.  grep the kernel headers and you'll 
> see a ton of [u]intXX_t hits.

Now, keep in mind this is only true for headers exported to userspace.
But this is correct - which is the base of this conversation (Sam
suggesting that they should be warned about, and I suggested
auto-converting them.)

> this logic though means that the kernel should not be defining any structures 
> that the C library is defining (such as asm-generic/fcntl.h).  such structs 
> should get renamed the same way as __[us]XX types

This is also correct, at least for exported headers.  For
kernel-internal headers, it doesn't matter.  Unfortunately we do have at
least several cases of exported interfaces with globally visible names.

There is one other exception of note, which is a header file which can
only be included by the userspace *application*, using a nonportable
top-level include (either directly <linux/*> or indirectly via <sys/*>).
 In those cases we can be looser about at least structure names.  This
is common for ioctl structures.

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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