s390/debug: Add s390dbf kernel parameter

Problem determination using s390dbf logging sometimes requires changing
the default logging level or log area size. While this is possible
using sysfs interfaces, there is no easy way to adjust these parameters
for early boot code that emits logs before userspace is available.

Add an s390dbf kernel parameter to address this shortcoming. The
parameter can be used to specify log level and area size (in units of
pages). A level of '-' turns logging off for an area. Logs can be
identified by name or a shell-style pattern.

Parameter format:

  s390dbf=<name|pattern>:[<level>|-]:[<pages>][,...]

Example:

  s390dbf=cio*:6:128,sclp_err::2

Specified parameters are applied immediately during debug area
registration for regular log areas. For early, static debug areas,
log levels are changed during early_param() parsing, while size
changes are applied at arch_initcall-time.

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Tested-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions