Re: [PATCH v2 4/4] coding-style: add explanation about pr_fmt macro
From: Jonathan Corbet <corbet@lwn.net>
Date: 2019-09-14 07:50:26
Also in:
linux-doc, lkml
On Fri, 13 Sep 2019 19:03:00 -0300 André Almeida [off-list ref] wrote:
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.
So I've finally had a chance to take a real look at this...
quoted hunk ↗ jump to hunk
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
Honestly, I think that this is out of scope for a document on coding style. That document is already far too long for most people to read, I don't think we should load it down with more stuff that isn't directly style related. That said, the information can be useful. I wanted to say that it should go with the documentation of the pr_* macros but ... well ... um ... we don't seem to have a whole lot of that. Figures. I suspect this is more than you wanted to sign up for, but...IMO, the right thing to do is to fill printk.h with a nice set of kerneldoc comments describing how this stuff should be used, then to pull that information into the core-api manual, somewhere near our extensive discussion of printk formats. It's amazing that we lack docs for something so basic. Thanks, jon