Date: Wed, 14 Aug 2013 10:20:43 -0700
From: Sarah Sharp <sarah.a.sharp@linux.intel.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Joe Perches <joe@perches.com>, Xenia Ragiadakou <burzalodowa@gmail.com>,
        Jason Baron <jbaron@akamai.com>, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: Dynamic debug on by default?
Message-ID: <20130814172043.GB22934@xanatos>
References: <20130814164022.GA22934@xanatos>
 <1376499114.1949.81.camel@joe-AO722>
 <20130814170410.GA7668@kroah.com>
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On Wed, Aug 14, 2013 at 10:04:10AM -0700, Greg KH wrote:
> On Wed, Aug 14, 2013 at 09:51:54AM -0700, Joe Perches wrote:
> > On Wed, 2013-08-14 at 09:40 -0700, Sarah Sharp wrote:
> > > Hi Xenia,
> > > 
> > > I'm a bit confused.  I thought that debugging messages would be turned
> > > off by default for a module if CONFIG_DYNAMIC_DEBUG was turned on.  When
> > > I tested your patch to remove the CONFIG_USB_XHCI_HCD_DEBUGGING and just
> > > use dev_dbg, the messages from the xHCI driver appeared in dmesg by
> > > default.
> > > 
> > > That generates a lot of log spew.  We can have distros add a boot
> > > parameter option to turn off debug messages, but that boot parameter is
> > > limited to 1023 characters.  I'm concerned that if more drivers add
> > > dynamic debugging, the distros will eventually run out of space in the
> > > dynamic debugging boot parameter.  I know Greg was ripping out debugging
> > > config options in other USB drivers, so this is a bit concerning.
> > > 
> > > Jason, is there a way within the xHCI driver to say that dynamic
> > > debugging should be off by default?  I've looked through the
> > > documentation, and I can't find anything like that documented.
> > 
> > #undefine DEBUG
> > 
> > > I've attached my .config file, in case I have something misconfigured.
> > 
> > Because of:
> > 
> > drivers/usb/host/Makefile:ccflags-$(CONFIG_USB_DEBUG) := -DDEBUG
> 
> Yes, that's the problem, I'm trying to get rid of the CONFIG_USB_DEBUG
> flag, and I'm almost there.  There are some host controllers that still
> use it for some things that I have not cleaned up fully yet.

Do you think those patches will land in 3.12?  If not, I'll add an
#undefine DEBUG to xhci.h to avoid the log spew.

Sarah Sharp
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