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Diffstat (limited to 'Documentation/DMA-API.txt')
| -rw-r--r-- | Documentation/DMA-API.txt | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index d9aa43d78bc..5aceb88b3f8 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt @@ -676,8 +676,8 @@ this directory the following files can currently be found: dma-api/all_errors This file contains a numeric value. If this value is not equal to zero the debugging code will print a warning for every error it finds - into the kernel log. Be carefull with this - option. It can easily flood your logs. + into the kernel log. Be careful with this + option, as it can easily flood your logs. dma-api/disabled This read-only file contains the character 'Y' if the debugging code is disabled. This can @@ -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 |