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authorIngo Molnar <mingo@elte.hu>2009-06-07 11:36:02 +0200
committerIngo Molnar <mingo@elte.hu>2009-06-07 11:36:02 +0200
commit62a6f465f6572e1f28765c583c12753bb3e23715 (patch)
tree35ccf596b4abbeec9e1244f31e5b4e5d079899f5 /Documentation
parent56fdd18c7b89a2fac1dfe5d54750c9143867fdc4 (diff)
parentbdc2911cde7d18580a545483844d75fdb3551729 (diff)
downloadop-kernel-dev-62a6f465f6572e1f28765c583c12753bb3e23715.zip
op-kernel-dev-62a6f465f6572e1f28765c583c12753bb3e23715.tar.gz
Merge branch 'dma-debug/2.6.31' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/linux-2.6-iommu into core/iommu
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/DMA-API.txt12
-rw-r--r--Documentation/kernel-parameters.txt7
2 files changed, 19 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
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e2999cb..8f9e17c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -641,6 +641,13 @@ and is between 256 and 4096 characters. It is defined in the file
DMA-API debugging code disables itself because the
architectural default is too low.
+ dma_debug_driver=<driver_name>
+ With this option the DMA-API debugging driver
+ filter feature can be enabled at boot time. Just
+ pass the driver to filter for as the parameter.
+ The filter can be disabled or changed to another
+ driver later using sysfs.
+
dscc4.setup= [NET]
dtc3181e= [HW,SCSI]
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