The pr_fmt macro is useful to format log messages printed by pr_XXXX() functions. Add text to explain the purpose of it, how to use and an example. Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> --- Changes from v1: - Add Jonathan as explict Cc - Replace "include/printk.h" by "#include <linux/kernel.h> - Add note about #undef - Replace hardcore string by KBUILD_MODNAME at the example --- Documentation/process/coding-style.rst | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst index f4a2198187f9..1a33a933fbd3 100644 --- a/Documentation/process/coding-style.rst +++ b/Documentation/process/coding-style.rst @@ -819,7 +819,15 @@ which you should use to make sure messages are matched to the right device and driver, and are tagged with the right level: dev_err(), dev_warn(), dev_info(), and so forth. For messages that aren't associated with a particular device, <linux/printk.h> defines pr_notice(), pr_info(), -pr_warn(), pr_err(), etc. +pr_warn(), pr_err(), etc. It's possible to format pr_XXX() messages using the +macro pr_fmt() to prevent rewriting the style of messages. It should be +defined before ``#include <linux/kernel.h>``, to avoid compiler warning about +redefinitions, or just use ``#undef pr_fmt``. This is particularly useful for +adding the name of the module at the beginning of the message, for instance: + +.. code-block:: c + + #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt Coming up with good debugging messages can be quite a challenge; and once you have them, they can be a huge help for remote troubleshooting. However -- 2.23.0
