Re: Dynamic debug on by default?

From: Joe Perches
Date: Wed Aug 14 2013 - 12:52:01 EST

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

you probably want to turn this off


when dynamic_debug is on.


This will cause all pr_debug/dev_dbg statements to be
emitted without specific enabling via the dynamic_debug
control file.

(from include/linux/dynamic_debug.h)

#if defined DEBUG

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