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>

1 files changed, 6 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 8dd7248508a9..3d854c9ae53a 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=