Re: [PATCH] arch/tile: Add driver to enable access to the user dynamic network.

[Chris Metcalf <cmetcalf@tilera.com>]

[The question is how to use <linux/list.h> from within <asm/processor.h>.]

On 6/28/2010 3:34 PM, Arnd Bergmann wrote:
>> I think the only "true" fix would be to have a new <linux/list_types.h>
>> > header that provides list_head (and presumably hlist_head and
>> > hlist_node), which <linux/list.h> would include, as would our
>> > <asm/processor.h>.  This is certainly in line with recent
>> > header-separation changes (e.g. mm_types.h).  Would there be interest in
>> > a change like this?  I implemented it in my tree, and if it sounds
>> > plausible to you, I'll send out a git diff, but it looks pretty much
>> > exactly like this description :-)
>>     
> Yes, I think that would be a reasonable change.
>
> Another alternative might be to move the prefetch stuff from asm/processor.h
> to asm/prefetch.h on all architectures, which also breaks the dependency loop,
> unless I'm mistaken again

In principle I like the <asm/prefetch.h> idea, but I'm concerned that
the #include of <asm/system.h> from <linux/list.h> will recursively
include <asm/processor.h> on some platforms; for example, s390 and
xtensa include it directly.  We (tile) were including it indirectly via
<asm/irqflags.h>, though this seems to be a spurious include on our
part, but other platforms may also include it indirectly.  To be fair,
I'm not sure why <asm/system.h> is included from <linux/list.h>.  It
doesn't seem required for a tile build, at least, but no doubt it was
put there for some reason.

So, if there's a good reason for it to be there, I'd say that pushes us
back toward a separate <linux/list_types.h>.  Otherwise we can
investigate splitting out the prefetch content on every platform to
<asm/prefetch.h> (presumably creating some empty <asm/prefetch.h>
headers on architectures that just use the gcc builtin) and adding new
#includes of <asm/prefetch.h> to files that reference the prefetch
functionality.  Arnd and other list folks, what's your instinct?

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com