diff options
| author | Thomas Renninger <trenn@suse.de> | 2010-08-06 16:11:02 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-10-22 10:16:42 -0700 |
| commit | a648ec05bb950fae2f35d0490ddd6cf15010af72 (patch) | |
| tree | cde3ca36db486e51d85c31619bf67f8d60215179 /Documentation | |
| parent | fd89cfb8718753459fcea3fe6103d19de5e86c9b (diff) | |
Dynamic Debug: Introduce ddebug_query= boot parameter
Dynamic debug lacks the ability to enable debug messages at boot time.
One could patch initramfs or service startup scripts to write to
/sys/../dynamic_debug/control, but this sucks.
This patch makes it possible to pass a query in the same format one can
write to /sys/../dynamic_debug/control via boot param.
When dynamic debug gets initialized, this query will automatically be
applied.
Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: jbaron@redhat.com
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/dynamic-debug-howto.txt | 22 | ||||
| -rw-r--r-- | Documentation/kernel-parameters.txt | 7 |
2 files changed, 27 insertions, 2 deletions
diff --git a/Documentation/dynamic-debug-howto.txt b/Documentation/dynamic-debug-howto.txt index 674c5663d34..58ea64a9616 100644 --- a/Documentation/dynamic-debug-howto.txt +++ b/Documentation/dynamic-debug-howto.txt @@ -24,7 +24,7 @@ Dynamic debug has even more useful features: read to display the complete list of known debug statements, to help guide you Controlling dynamic debug Behaviour -=============================== +=================================== The behaviour of pr_debug()/dev_debug()s are controlled via writing to a control file in the 'debugfs' filesystem. Thus, you must first mount the debugfs @@ -212,6 +212,26 @@ Note the regexp ^[-+=][scp]+$ matches a flags specification. Note also that there is no convenient syntax to remove all the flags at once, you need to use "-psc". + +Debug messages during boot process +================================== + +To be able to activate debug messages during the boot process, +even before userspace and debugfs exists, use the boot parameter: +ddebug_query="QUERY" + +QUERY follows the syntax described above, but must not exceed 1023 +characters. The enablement of debug messages is done as an arch_initcall. +Thus you can enable debug messages in all code processed after this +arch_initcall via this boot parameter. +On an x86 system for example ACPI enablement is a subsys_initcall and +ddebug_query="file ec.c +p" +will show early Embedded Controller transactions during ACPI setup if +your machine (typically a laptop) has an Embedded Controller. +PCI (or other devices) initialization also is a hot candidate for using +this boot parameter for debugging purposes. + + Examples ======== diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 8dd7248508a..3d854c9ae53 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -43,10 +43,11 @@ parameter is applicable: AVR32 AVR32 architecture is enabled. AX25 Appropriate AX.25 support is enabled. BLACKFIN Blackfin architecture is enabled. - DRM Direct Rendering Management support is enabled. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled EFI EFI Partitioning (GPT) is enabled EIDE EIDE/ATAPI support is enabled. + DRM Direct Rendering Management support is enabled. + DYNAMIC_DEBUG Build in debug messages and enable them at runtime FB The frame buffer device is enabled. GCOV GCOV profiling is enabled. HW Appropriate hardware is enabled. @@ -570,6 +571,10 @@ and is between 256 and 4096 characters. It is defined in the file Format: <port#>,<type> See also Documentation/input/joystick-parport.txt + ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot + time. See Documentation/dynamic-debug-howto.txt for + details. + debug [KNL] Enable kernel debugging (events log level). debug_locks_verbose= |