This patch adds documentation that clarifies the use of various diagnostic printing messages. It shows the preference of subsystem_dbg calls to dev_dbg (whenever possible), as the first preferred format of logging debug messages. Signed-off-by: Yogesh Chaudhari <mr.yog...@gmail.com> --- Documentation/CodingStyle | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle index 7fe0546..cd14cc8 100644 --- a/Documentation/CodingStyle +++ b/Documentation/CodingStyle @@ -662,6 +662,23 @@ 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_debug() and pr_info(). +If the subsystem has its own diagnostic macros then they should be used +instead of dev_dbg calls. +E.g. If you are using network subsystem, use netdev_dbg; +if you are using V4L, use v4l_dbg etc. +This standardises the output format in every subsystem. + +Depending on your changes, the following order of precedence +applies to printing messages: +1. [subsystem]_dbg() is preferred when the subsystem has its own +diagnostic macros. +2. dev_dbg() is preferred when you have a generic struct device object. +3. pr_debug() should be used when 1 and 2 above are not applicable. +4. printk() should be avoided. + +Note: The above order applies to diagnostic calls of all log levels viz: +*_emerg, *_alert, *_crit, *_err, *_warn, *_notice, *_info and *_dbg. + 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. Such messages should be compiled out when the DEBUG symbol is not defined (that -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
