printk or pr_<level>?
Arlie Stephens
arlie at worldash.org
Thu Jul 24 14:36:25 EDT 2014
Thank-you Greg
On Jul 23 2014, Greg KH wrote:
>
> On Wed, Jul 23, 2014 at 02:45:05PM -0700, Arlie Stephens wrote:
> > On Jul 23 2014, Kristofer Hallin wrote:
> >
> > > 1. No. Depending on what subsystem your are printing logs from you
> > > should use different functions for logging. In the networking
> > > subsystem netdev_dbg is suitable and so on. Otherwise pr_debug will
> > > always work and is always preferred over printk.
> >
> > Why?
[snip]
> Ok, here's the rule in one sentance:
> Be as _descriptive_ as you can with the device that is emitting
> the message.
>
> So what does that mean in reality?
>
> Use the subsystem's logging macros for your messages. If you are not in
> a subsystem, then fall back to the "default" pr_* messages.
>
> So, if you are a network driver, then use netdev_dbg(). Other
> subsystems of "class" devices have their own form of logging macros, and
> they should be easy to find.
>
> If you aren't in a class driver, but are a driver, then use dev_dbg(),
> because you do have a device pointer accessable to you (if you don't,
> either you are in your module init or exit function, and you shouldn't
> be printing messages then anyway.)
>
> If you are not in a driver, and you do not have _any_ 'struct device'
> accessable to you, reconsider if you really want to be printing
> anything, as the use of it to a user is going to be really low. But if
> you have to, then fall back to the pr_* functions, as those tie into the
> dynamic debugging logic of the kernel, and provide a format that is
> unified that userspace tools can use to hopefully search and find things
> properly.
>
> So there is a method to this madness, and it is pretty simple if you
> think about it this way.
>
> Does that help out?
Yes it does. Thank you.
And I think I see why I needed help - I'm mentally a "core kernel"
person, whatever I may happen to be working on at the moment ;-)
So my archetypal kernel message would be something like the ones
generated by BUG_ON() ;-)
>
> greg k-h
--
Arlie
(Arlie Stephens arlie at worldash.org)
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