Re: [PATCH 2/2] i2c-hid: remove mostly useless parameter 'debug'

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Fri, 2013-08-02 at 20:14 +0200, Benjamin Tissoires wrote: 
> On 02/08/13 16:49, Andy Shevchenko wrote:
> > On Fri, 2013-08-02 at 16:30 +0200, Benjamin Tissoires wrote: 

[]

> >> Moreover, the dev_dbg calls are compiled out if DEBUG symbol is not
> >> set.
> > 
> > Yes, and what is the difference between previously used
> > if (debug)
> >   dev_dbg(...)
> > 
> > ?
> 
> That's because the previous code was directly using
> dev_printk(KERN_DEBUG,...) and not dev_dbg() within the condition.
> 
> This call does not use dynamic debugging or does not get compiled out if
> DEBUG is not set.

Yeah, I've checked this just after I sent the message.

> Also, to my defence, I can add that I developed this driver on an ARM
> board without dynamic debugging support enabled... :)


So, the problem is DYNAMIC_DEBUG is not default option in kernel (and I
could imagine why).

I checked few distros for that: Debian/Ubuntu - off,
Fedora/OpenSuse/ArchLinux - on.

Just to understand what kind of user might run this with debug? Is it
developer or person who knows the subject? If it's not a such person, it
would be difficult  to him or her to enable dynamic debug in distros
like Ubuntu, which sucks.

> >> So, if we ever have to change this debug variable, I would prefer
> >> using the hid debug environment which would at least limit the number
> >> of debug outputs to the HID subsystem.
> > 
> > Usually when I see such code I understood it was written in
> > pre-dynamic-debug epoch. So, my point is to switch to dynamic debug and
> > use it efficiently.
> 
> Ok, so if you can guarantee me that adding the proper kernel parameter
> will allow me to retrieve all the i2c-hid logs from the boot, then I'd
> be happy to ack this. However, I have no way to test this right now, so
> I'll need to trust you (that's why I'm asking you to do proper testing).

With only one condition if dynamic debug is enabled in kernel.
So, it would be nice to gather opinions, however, the decision is
totally depends on type of user who wants to debug the module.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy