From 1745de5e5639457513fe43440f2800e23c3cbc7d Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 22 May 2009 21:49:51 +0200 Subject: dma-debug: add dma_debug_driver kernel command line This patch add the dma_debug_driver= boot parameter to enable the driver filter for early boot. Signed-off-by: Joerg Roedel --- Documentation/kernel-parameters.txt | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'Documentation') diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index e87bdbfbcc7..b3f1314588c 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -646,6 +646,13 @@ 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= + 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] -- cgit v1.2.3 From 016ea6874a6d58df85b54f56997d26df13c307b2 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 22 May 2009 21:57:23 +0200 Subject: 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 --- Documentation/DMA-API.txt | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'Documentation') 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= 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 -- cgit v1.2.3