1 files changed, 55 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index aa81d2848448..31d784dd80d0 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -807,6 +807,61 @@ menuconfig BUILD_DOCSRC
 
           Say N if you are unsure.
 
+config DYNAMIC_PRINTK_DEBUG
+        bool "Enable dynamic printk() call support"
+        default n
+        depends on PRINTK
+        select PRINTK_DEBUG
+        help
+
+          Compiles debug level messages into the kernel, which would not
+          otherwise be available at runtime. These messages can then be
+          enabled/disabled on a per module basis. This mechanism implicitly
+          enables all pr_debug() and dev_dbg() calls. The impact of this
+          compile option is a larger kernel text size of about 2%.
+
+          Usage:
+
+          Dynamic debugging is controlled by the debugfs file,
+          dynamic_printk/modules. This file contains a list of the modules that
+          can be enabled. The format of the file is the module name, followed
+          by a set of flags that can be enabled. The first flag is always the
+          'enabled' flag. For example:
+
+                <module_name> <enabled=0/1>
+                                .
+                                .
+                                .
+
+          <module_name> : Name of the module in which the debug call resides
+          <enabled=0/1> : whether the messages are enabled or not
+
+          From a live system:
+
+                snd_hda_intel enabled=0
+                fixup enabled=0
+                driver enabled=0
+
+          Enable a module:
+
+                $echo "set enabled=1 <module_name>" > dynamic_printk/modules
+
+          Disable a module:
+
+                $echo "set enabled=0 <module_name>" > dynamic_printk/modules
+
+          Enable all modules:
+
+                $echo "set enabled=1 all" > dynamic_printk/modules
+
+          Disable all modules:
+
+                $echo "set enabled=0 all" > dynamic_printk/modules
+
+          Finally, passing "dynamic_printk" at the command line enables
+          debugging for all modules. This mode can be turned off via the above
+          disable command.
+
 source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"