From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Greg KH <greg@kroah.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: User mode drivers: part 2: PCI device handling (patch 1/2 for 2.6.11)
Date: Mon, 14 Mar 2005 17:46:02 +0000 [thread overview]
Message-ID: <1110822361.17740.141.camel@localhost.localdomain> (raw)
In-Reply-To: <16948.55096.598031.618338@wombat.chubb.wattle.id.au>
On Llu, 2005-03-14 at 00:13, Peter Chubb wrote:
> Greg> see mmap(2)
>
> mmap maps a file's contents into your own virtual memory.
> usr_pci_map maps part of your own virtual memory into pci bus space
> for a particular device (using the IOMMU if your machine has one), and
> returns a scatterlist of bus addresses to hand to the device.
You can't really do it that way around because you don't know what the
memory constraints of the device are compared to your user pages.
Suppose your user pages are in high memory over 4GB and the device is
32bit DMA constrained ? You don't want bounce buffers clearly.
In addition you have to be very careful about shared pages when doing
DMA because you don't want to DMA into a COW page but that is handleable
(as is done by O_DIRECT)
Alan
next prev parent reply other threads:[~2005-03-14 17:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-11 3:37 User mode drivers: part 2: PCI device handling (patch 1/2 for 2.6.11) Peter Chubb
2005-03-11 7:18 ` Greg KH
2005-03-11 8:34 ` Peter Chubb
2005-03-11 10:31 ` Pavel Machek
2005-03-11 15:21 ` Greg KH
2005-03-11 16:45 ` Jesse Barnes
2005-03-12 22:43 ` Jon Smirl
2005-03-14 0:13 ` Peter Chubb
2005-03-14 17:46 ` Alan Cox [this message]
2005-03-11 19:16 ` Alan Cox
2005-03-12 10:49 ` Andrew Grover
-- strict thread matches above, loose matches on Subject: below --
2005-03-11 5:18 Albert Cahalan
2005-03-11 19:15 ` Alan Cox
2005-03-11 21:04 ` Albert Cahalan
2005-03-14 13:34 ` Alan Cox
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