Messages in this thread | | | From | "Alan Shih" <> | Subject | RE: Question regarding DMA xfer to user space directly | Date | Wed, 9 Jul 2003 10:35:15 -0700 |
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Next question would be what are the steps that the driver need to ping user pages before setting up the xfer?
Thanks.
-----Original Message----- From: Alan Cox [mailto:alan@lxorguk.ukuu.org.uk] Sent: Tuesday, July 08, 2003 8:22 AM To: Alan Shih Cc: Linux Kernel Mailing List Subject: Re: Question regarding DMA xfer to user space directly
On Maw, 2003-07-08 at 15:50, Alan Shih wrote: > Is there a provision in MM for DMA transfer to user space directly without > allocating a kernel buffer?
Yes. Its used both for O_DIRECT I/O (direct to disk I/O from userspace) and for things like tv capture cards. The kernel allows a driver to pin user pages and obtain mappings for them. Note that for large systems user pages may be above the 32bit boundary so you need DAC capable hardware to get the best results
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