lkml.org 
[lkml]   [2010]   [Oct]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: Question: how to copy to user space from a tasklet
Date
On Friday 15 October 2010 07:57:59 Stefan Richter wrote:
> Tom Brown wrote:
> > [Sorry to have to ask this here - I can't find any driver-specific
> > newsgroup or mailing lists - are there any??]
>
> linux-newbie perhaps.
>
> > I have a driver which needs to copy device data direct to user space
> > from a tasklet.
>
> One way would be to use mmap() to allocate the DMA buffer and insert it into
> the user address space before DMA commences. An additional poll/read/write
> based protocol or so can be used for buffer management during DMA.

Agreed, that would be best, it's a lot easier than the way Tom describes
the driver to work today.

Just for completeness: doing DMA to random user address would require the
process to register the area using some home grown interface, so that the
driver can do get_user_pages/kmap on all of them and subsequently pass
around an array of pages, while keeping track of ulimits and coherency
with the existing kernel mappings. Don't do that.

Arnd


\
 
 \ /
  Last update: 2010-10-15 11:03    [W:0.069 / U:0.696 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site