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From: "André Almeida" <>
	"André Almeida" <>
Subject: [PATCH 4/4] coding-style: add explanation about pr_fmt macro
Date: Fri, 13 Sep 2019 15:57:46 -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 <>
 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..276787bc2ff2 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 including ``include/printk.h``, to avoid compiler warning about
+redefinitions. 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) "module_name: " 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 18:57 [PATCH 0/4] null_blk: fixes around nr_devices and log improvements André Almeida
2019-09-13 18:57 ` [PATCH 1/4] null_blk: do not fail the module load with zero devices André Almeida
2019-09-13 18:57 ` [PATCH 2/4] null_blk: match the type of parameter nr_devices André Almeida
2019-09-13 18:57 ` [PATCH 3/4] null_blk: format pr_* logs with pr_fmt André Almeida
2019-09-13 20:18   ` Chaitanya Kulkarni
2019-09-13 18:57 ` André Almeida [this message]
2019-09-13 19:08   ` [PATCH 4/4] coding-style: add explanation about pr_fmt macro Joe Perches
2019-09-13 19:36     ` André Almeida
2019-09-13 20:22   ` Bart Van Assche
2019-09-14  7:08     ` Jonathan Corbet
2019-09-13 19:03 ` [PATCH 0/4] null_blk: fixes around nr_devices and log improvements Jens Axboe
2019-09-13 19:22   ` André Almeida
2019-09-13 20:50     ` Jens Axboe

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