scripts/checkpatch.pl

[Yogesh Chaudhari]

Hello,

I recently ran "scripts/checkpatch.pl" after adding the simplest form
of "hello world" module to the source tree. I used the old "printk"s
in this module and got this warning message:

WARNING: Prefer netdev_dbg(netdev, ... then dev_dbg(dev, ... then
pr_debug(...  to printk(KERN_DEBUG ...

It has come to my understanding that the dynamic debugging interface
offered by pr_debug and dev_dbg have obvious advantages to printk and
therefore they are preferred to printk.

Even amongst dev_dbg and pr_debug, we prefer dev_dbg if we have a
struct device to standardize device information output along with our
debug message. It offers escape from the "edit/rebuild/reboot cycle"
and also allows to maintain a neat log through dynamic_debug/control
interface.

I was not clear as to why netdev_dbg would be preferred to dev_dbg and
was given this asnwer on stackoverflow:

http://stackoverflow.com/questions/22077540/order-of-preference-printk-vs-dev-dbg-vs-netdev-dbg

Particularly, in regards to this part:
"netdev_dbg it is not the absolutly prefered print style. It is
prefered if you are working with a netdevice."

If this is the case, then I think the WARNING message should be
modified to mention that [subsystem]_dbg is preferred over dev_dbg. In
case this is correct and I am not missing something, I would like to
propose a patch to modify this script to give appropriate error
message. But in case I am wrong about this I would like
comments/suggestions/explanations before starting anything.

Thanks
Yogesh
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