linux-kernel - Dynamic debug on by default?

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Date:	Wed, 14 Aug 2013 09:40:22 -0700
From:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
To:	Xenia Ragiadakou <burzalodowa@...il.com>,
	Jason Baron <jbaron@...mai.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Dynamic debug on by default?

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.

I've attached my .config file, in case I have something misconfigured.

Sarah Sharp

View attachment ".config" of type "text/plain" (101848 bytes)