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authorJoerg Roedel <joerg.roedel@amd.com>2009-05-22 21:57:23 +0200
committerJoerg Roedel <joerg.roedel@amd.com>2009-06-02 16:21:42 +0200
commit016ea6874a6d58df85b54f56997d26df13c307b2 (patch)
treec81215544023864104a840384a215aa5e3e43db7
parent1745de5e5639457513fe43440f2800e23c3cbc7d (diff)
downloadlinux-016ea6874a6d58df85b54f56997d26df13c307b2.tar.gz
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@amd.com>
-rw-r--r--Documentation/DMA-API.txt12
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index d9aa43d78bc..25fb8bcf32a 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