From: Matt Porter <mporter@kernel.crashing.org>
To: Oliver King-Smith <oliver.king-smith@nuvation.com>
Cc: "'linuxppc-embedded@lists.linuxppc.org'"
<linuxppc-embedded@lists.linuxppc.org>
Subject: Re: Problem trying to address custom hardware
Date: Wed, 25 Aug 2004 16:05:25 -0700 [thread overview]
Message-ID: <20040825160525.F9986@home.com> (raw)
In-Reply-To: <FC3C0DD86B79DF4FA423AF0379A5476101554372@mailguy2.nuvation.com>; from oliver.king-smith@nuvation.com on Wed, Aug 25, 2004 at 03:29:20PM -0700
On Wed, Aug 25, 2004 at 03:29:20PM -0700, Oliver King-Smith wrote:
>
> Things are working much better. Both the driver and the main code work
> without crashing now.
>
> > Others addressed your core problem, but you should know that this
> > mmap request won't produce the desired result. You need MAP_SHARED
> > since MAP_PRIVATE will result in a COW when you attempt to modify
> > your register.
>
> I am not sure I understand why this needs to be MAP_SHARED (it sure does
> though). Is there a good resource I can read to understand this a bit
> better?
The mmap(2) manpage explains the difference pretty well. MAP_PRIVATE
indicates that any modification are local to the process. So, as
soon as you write to it, it makes a copy of the page for your process
to modify. MAP_SHARED indicates that any modifications are seen by
any processes that also map the region.
googling will probably yield many threads on lkml on this topic.
-Matt
** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
next prev parent reply other threads:[~2004-08-25 23:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-25 22:29 Problem trying to address custom hardware Oliver King-Smith
2004-08-25 23:05 ` Matt Porter [this message]
-- strict thread matches above, loose matches on Subject: below --
2004-08-25 7:50 Rupesh S
2004-08-24 23:10 Oliver King-Smith
2004-08-25 5:56 ` Eugene Surovegin
2004-08-25 17:40 ` Matt Porter
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