[lkml]   [2009]   [Jul]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Should I use kmap or kmap_atomic to map user pages that will be written in a loop ?
On Sat, 25 Jul 2009 23:41:47 +0200
Laurent Pinchart <> wrote:

> Pages will be written to from the kernel in USB interrupt context. I can then
> either kmap_atomic() pages before copying data and kunmap_atomic() them right
> after, or kmap() them once at the beginning of the video stream and keep them
> mapped until the end.

Video buffers can be big, and the streaming interface requires at least
two of them. That's a lot of kmap'd pages. It seems to me that
kmap_atomic() is the way to go for something like this.

But, then, these are user-space buffers, and you're seemingly buffering
the data through kernel space buffers first? It seems like using
copy_to_user() in a workqueue (or a threaded interrupt handler) might be
a more straightforward way to go, unless I'm missing something.


 \ /
  Last update: 2009-07-26 23:31    [W:0.062 / U:4.164 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site