From: Helge Hafting <helgehaf@idb.hist.no>
To: Sebastian Heidl <heidl@zib.de>, linux-kernel@vger.kernel.org
Subject: Re: DMA to/from user buffers
Date: Wed, 05 Sep 2001 09:51:22 +0200 [thread overview]
Message-ID: <3B95D97A.DB82E0C4@idb.hist.no> (raw)
In-Reply-To: <20010904164509.A27144@csr-pc1.zib.de>
Sebastian Heidl wrote:
>
> Hi,
>
> two questions about using an user-supplied buffer (e.g. malloced
> in user space) for DMA transfers:
>
> 1. Is it possible ?
> 2. What restrictions/requirements apply for the buffer (alignment...) ?
There are some obvious problems with this. First, a malloc'ed
buffer might not be in memory. It might not be created yet if you
haven't touched it, and it might be on swap if you have.
The recommended way is to allocate in the kernel, (probably by
the driver that want to do DMA), and mmap this buffer into
userspace.
Helge Hafting
prev parent reply other threads:[~2001-09-05 7:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-04 14:45 DMA to/from user buffers Sebastian Heidl
2001-09-04 19:30 ` Gerd Knorr
2001-09-05 7:51 ` Helge Hafting [this message]
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