From: Russ Cox <russcox@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] kernel - kmap/KADDR ?
Date: Sat, 27 Nov 2004 19:54:46 -0500 [thread overview]
Message-ID: <ee9e417a0411271654304afe6d@mail.gmail.com> (raw)
In-Reply-To: <Pine.BSI.4.58.0411271141430.6130@malasada.lava.net>
> I'm confused about the usage of kmap and KADDR in the code. I
> had assumed that kmap() was used to map a page into kernel memory,
> and kunmap() was used to unmap that page. I just noticed that the
> KADDR() macro is used in the port code in a similar way. The
> port code calls KADDR on a physical addr, and then starts reading
> and writing the returned address.
KADDR is only used to access the physical memory occupied
by the kernel and its data. Kmap/kunmap are used to access the
whole of physical memory. So they're not redundant, and that's
why there's no unmap for KADDR.
Kmap/kunmap are exactly what you think they are.
Russ
prev parent reply other threads:[~2004-11-28 0:54 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-27 21:50 Tim Newsham
2004-11-28 0:54 ` Russ Cox [this message]
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