printk: add module parameter ignore_loglevel to control ignore_loglevel

We are enabling some power features on medfield.  To test suspend-2-RAM
conveniently, we need turn on/off ignore_loglevel frequently without
rebooting.

Add a module parameter, so users can change it by:
/sys/module/printk/parameters/ignore_loglevel

Signed-off-by: Yanmin Zhang <yanmin.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 27e0488d54d2..106efe1e2bab 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -973,6 +973,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
         ignore_loglevel [KNL]
                         Ignore loglevel setting - this will print /all/
                         kernel messages to the console. Useful for debugging.
+                        We also add it as printk module parameter, so users
+                        could change it dynamically, usually by
+                        /sys/module/printk/parameters/ignore_loglevel.
 
         ihash_entries=  [KNL]
                         Set number of hash buckets for inode cache.
diff --git a/kernel/printk.c b/kernel/printk.c
index b7da18391c38..e62f949ec140 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -532,6 +532,9 @@ static int __init ignore_loglevel_setup(char *str)
 }
 
 early_param("ignore_loglevel", ignore_loglevel_setup);
+module_param_named(ignore_loglevel, ignore_loglevel, bool, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
+        "print all kernel messages to the console.");
 
 /*
  * Write out chars from start to end - 1 inclusive