lkml.org 
[lkml]   [2008]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/1] Userspace I/O (UIO): Add support for userspace DMA (corrected)
On Wed, Dec 03, 2008 at 05:51:30PM -0800, Edward Estabrook wrote:
> From: Edward Estabrook <Edward_Estabrook@agilent.com>
>
> Here is a patch that adds the ability to dynamically allocate and use
> coherent DMA
> from userspace by extending the Userspace IO driver. This patch applies against
> 2.6.28-rc6.
>
> The gist of this implementation is to overload uio's mmap
> functionality to allocate
> and map a new DMA region on demand. The bus-specific DMA address as returned by
> dma_alloc_coherent is made available to userspace in the 1st long word
> of the newly
> created region (as well as through the conventional 'addr' file in sysfs).
>
> The kernel-api change is that passing an offset value of 0xFFFFF000UL
> to the a uio
> device's mmap operation will dynamically allocate a DMA region. This
> cannot change/
> break existing behavior as the previous UIO code only allowed a maximum of 5
> mappings.

Odd formatting of your paragraphs :(

Anyway, what about 64bit processors? What happens if they try to use a
valid address in this range?

Is this value always an "invalid" value for all arches that Linux runs
on?

thanks,

greg k-h


\
 
 \ /
  Last update: 2008-12-04 05:49    [W:0.492 / U:3.168 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site