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Message-ID: <1243953404-31799-5-git-send-email-joerg.roedel@amd.com>
Date: Tue, 2 Jun 2009 16:36:44 +0200
From: Joerg Roedel <joerg.roedel@....com>
To: iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
CC: akpm@...ux-foundation.org, Joerg Roedel <joerg.roedel@....com>
Subject: [PATCH 4/4] dma-debug: add documentation for the driver filter
This patch adds the driver filter feature to the dma-debug
documentation.
Signed-off-by: Joerg Roedel <joerg.roedel@....com>
---
Documentation/DMA-API.txt | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index d9aa43d..25fb8bc 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -704,12 +704,24 @@ this directory the following files can currently be found:
The current number of free dma_debug_entries
in the allocator.
+ dma-api/driver-filter
+ You can write a name of a driver into this file
+ to limit the debug output to requests from that
+ particular driver. Write an empty string to
+ that file to disable the filter and see
+ all errors again.
+
If you have this code compiled into your kernel it will be enabled by default.
If you want to boot without the bookkeeping anyway you can provide
'dma_debug=off' as a boot parameter. This will disable DMA-API debugging.
Notice that you can not enable it again at runtime. You have to reboot to do
so.
+If you want to see debug messages only for a special device driver you can
+specify the dma_debug_driver=<drivername> parameter. This will enable the
+driver filter at boot time. The debug code will only print errors for that
+driver afterwards. This filter can be disabled or changed later using debugfs.
+
When the code disables itself at runtime this is most likely because it ran
out of dma_debug_entries. These entries are preallocated at boot. The number
of preallocated entries is defined per architecture. If it is too low for you
--
1.6.3.1
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