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Message-ID: <517f3f820901031048p36e65f92l20bb7250cc4d82e5@mail.gmail.com> Date: Sun, 4 Jan 2009 07:48:39 +1300 From: "Michael Kerrisk" <mtk.manpages@...il.com> To: "Jason Baron" <jbaron@...hat.com> Cc: "Tilman Schmidt" <t.schmidt@...enixsoftware.de>, linux-kernel@...r.kernel.org, "Michael Kerrisk" <mtk.manpages@...il.com> Subject: Re: dynamic_printk documentation On Wed, Dec 24, 2008 at 5:22 AM, Jason Baron <jbaron@...hat.com> wrote: > On Tue, Dec 23, 2008 at 01:25:25PM +0100, Tilman Schmidt wrote: >> Where is the current debugfs interface to dynamic_printk documented? >> From the source in lib/dynamic_printk.c I deduced that >> >> echo "set enable=1 <module_name>" > /sys/kernel/debug/dynamic_printk/modules >> >> should enable debug output for module <module_name>, and verified >> experimentally that this does indeed work. Is that already described >> somewhere I just overlooked? If not, I would propose creating a file >> Documentation/dynamic_printk.txt. >> >> Thanks, >> Tilman > > hi, > > Most of it is with the config parameter definition in lib/Kconfig.debug > (copied below). I can propose copying it into Documentation/ if you think it'd > be useful. That would make some sense. Kconfig isn't usually the place where where one expects to look for usage documentation. Cheers, Michael > config DYNAMIC_PRINTK_DEBUG > bool "Enable dynamic printk() call support" > default n > depends on PRINTK > select PRINTK_DEBUG > help > > Compiles debug level messages into the kernel, which would not > otherwise be available at runtime. These messages can then be > enabled/disabled on a per module basis. This mechanism implicitly > enables all pr_debug() and dev_dbg() calls. The impact of this > compile option is a larger kernel text size of about 2%. > > Usage: > > Dynamic debugging is controlled by the debugfs file, > dynamic_printk/modules. This file contains a list of the modules that > can be enabled. The format of the file is the module name, followed > by a set of flags that can be enabled. The first flag is always the > 'enabled' flag. For example: > > <module_name> <enabled=0/1> > . > . > . > > <module_name> : Name of the module in which the debug call resides > <enabled=0/1> : whether the messages are enabled or not > > From a live system: > > snd_hda_intel enabled=0 > fixup enabled=0 > driver enabled=0 > > Enable a module: > > $echo "set enabled=1 <module_name>" > dynamic_printk/modules > > Disable a module: > > $echo "set enabled=0 <module_name>" > dynamic_printk/modules > > Enable all modules: > > $echo "set enabled=1 all" > dynamic_printk/modules > > Disable all modules: > > $echo "set enabled=0 all" > dynamic_printk/modules > > Finally, passing "dynamic_printk" at the command line enables > debugging for all modules. This mode can be turned off via the above > disable command. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Found a documentation bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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