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From: "André Almeida" <>
	"André Almeida" <>
Subject: [PATCH v2 4/4] coding-style: add explanation about pr_fmt macro
Date: Fri, 13 Sep 2019 19:03:00 -0300
Message-ID: <> (raw)
In-Reply-To: <>

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

Signed-off-by: André Almeida <>
Cc: Jonathan Corbet <>
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

  parent reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-13 22:02 [PATCH v2 0/4] null_blk: fixes around nr_devices and log improvements André Almeida
2019-09-13 22:02 ` [PATCH v2 1/4] null_blk: do not fail the module load with zero devices André Almeida
2019-09-13 22:15   ` Chaitanya Kulkarni
2019-09-13 22:17   ` Bart Van Assche
2019-09-13 22:37     ` Chaitanya Kulkarni
2019-09-13 22:02 ` [PATCH v2 2/4] null_blk: match the type of parameter nr_devices André Almeida
2019-09-13 22:15   ` Chaitanya Kulkarni
2019-09-13 22:02 ` [PATCH v2 3/4] null_blk: format pr_* logs with pr_fmt André Almeida
2019-09-13 22:16   ` Chaitanya Kulkarni
2019-09-13 22:03 ` André Almeida [this message]
2019-09-13 22:18   ` [PATCH v2 4/4] coding-style: add explanation about pr_fmt macro Chaitanya Kulkarni
2019-09-14  7:50   ` Jonathan Corbet
2019-09-16 13:38     ` André Almeida

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