printk: add ignore_loglevel as module parameter

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 could change it by:
/sys/module/printk/parameters/ignore_loglevel

Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Signed-off-by: Andrew Morton <>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b8e038dc41cb4e1e029893376d46cfce98d6eb5f..45b697559947a3b932732effcddc1bdbf2635d3f 100644 (file)
--- 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 92d13358cea5a962aa6e35dc07b0fef1059acb83..e62f949ec14075fd11c0517c9f20514b8a4bc2d0 100644 (file)
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -533,6 +533,8 @@ 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