lkml.org 
[lkml]   [2002]   [Sep]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: Streaming DMA mapping question
From
   From: Adam Kropelin <akropel1@rochester.rr.com>
Date: Fri, 13 Sep 2002 15:39:16 -0400

According to the docs, you should either unmap or sync your DMA buffer before
touching it from the host. The i386 implementation of pci_unmap is empty --no
problem; there must not be any unmap work to do on this arch. But the
implementation of pci_dma_sync does contain a flush_write_buffers() call. This
makes me think that perhaps if I'm going to modify the buffer before I submit it
back to the controller I need to do:

Actually, rather it appears that the i386 pci_unmap_*() routines need
the write buffer flush as well.

The x86 implementation is a bad example to read if you're trying to
see what the worst case scenerio is.

Just follow the document and your driver will work properly on all
platforms. DMA-mapping.txt was meant to be written in a way such
that you should not ever need to look at an implementation of the
interfaces to figure out how to use them.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:28    [W:0.093 / U:1.664 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site