CONFIG_SND_DEBUG

[Takashi Iwai]

At Wed, 05 Jun 2013 13:38:55 +0200,
David Henningsson wrote:
> 
> On 06/05/2013 12:53 PM, Andy Whitcroft wrote:
> > On Wed, Jun 05, 2013 at 09:47:30AM +0200, David Henningsson wrote:
> >>>>> On Wed, 2013-06-05 at 08:54 +0200, Takashi Iwai wrote:
> >>>>>> At Tue, 04 Jun 2013 23:52:01 -0700, Joe Perches wrote:
> >>>>>>> On Wed, 2013-06-05 at 08:32 +0200, Takashi Iwai wrote:
> >>>>>>>> Yes.  These are snd_printd() just to be conditionally built in.
> >>>>>>>> But in most cases it's rather useful to print them (as most distros
> >>>>>>>> set CONFIG_SND_DEBUG=y).
> >>>>>>> Ubuntu doesn't,  I believe Fedora doesn't.
> >>>>>> Then they should have done so :)
> >>>>> But they don't, so what distros do?
> >>>>
> >>>> RedHat (including Fedora) and SUSE do at least.
> >>>
> >>> Mandriva does too.  (still looking around for others)
> >>>
> >>> We can ask Ubuntu to enable CONFIG_SND_DEBUG.
> >>> (cc'd Andy Whitcroft, Leann Ogasawara and David Henningsson)
> >>>
> >>> Maybe there are others Canonical folk that
> >>> should be cc'd?
> >>
> >> Adding kernel team mailing list to CC.
> >>
> >> Andy/Leann - apparently CONFIG_SND_DEBUG is on by default from
> >> upstream, and we explicitly disable it. Is there any reason why we
> >> do that?
> >
> > config SND_DEBUG
> >          bool "Debug"
> >          help
> >            Say Y here to enable ALSA debug code.
> >
> > It is off by default in upstream, and the really helpful description
> > would cirtainly tend to lead to it being disabled.  But if it is helpful
> > to your debugging efforts David then I suspect we can enable it in Saucy
> > and see what happens.
> 
> Okay, so then the ball is back in Takashi's area - if we're recommended 
> to turn CONFIG_SND_DEBUG on, why is it off by default in the upstream 
> Linux kernel?

It's not off as default.  Simply there is no default, just like most
of other options.

As already mentioned, if the device is known to work well with the
kernel, there is no reason to set it on.  Then it'll saves the memory
and code space.  That is, for custom kernels, it's good to be off.
But for generic kernels like distro kernel, it'd be better to take a
safer side with more safety checks that is built in by that option.


Takashi