linux/scripts/basic/hash.c
Jason Baron 346e15beb5 driver core: basic infrastructure for per-module dynamic debug messages
Base infrastructure to enable per-module debug messages.

I've introduced CONFIG_DYNAMIC_PRINTK_DEBUG, which when enabled centralizes
control of debugging statements on a per-module basis in one /proc file,
currently, <debugfs>/dynamic_printk/modules. When, CONFIG_DYNAMIC_PRINTK_DEBUG,
is not set, debugging statements can still be enabled as before, often by
defining 'DEBUG' for the proper compilation unit. Thus, this patch set has no
affect when CONFIG_DYNAMIC_PRINTK_DEBUG is not set.

The infrastructure currently ties into all pr_debug() and dev_dbg() calls. That
is, if CONFIG_DYNAMIC_PRINTK_DEBUG is set, all pr_debug() and dev_dbg() calls
can be dynamically enabled/disabled on a per-module basis.

Future plans include extending this functionality to subsystems, that define 
their own debug levels and flags.

Usage:

Dynamic debugging is controlled by the debugfs file, 
<debugfs>/dynamic_printk/modules. This file contains a list of the modules that
can be enabled. The format of the file is as follows:

	<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

For example:

	snd_hda_intel enabled=0
	fixup enabled=1
	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.

[gkh: minor cleanups and tweaks to make the build work quietly]

Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2008-10-16 09:24:47 -07:00

65 lines
1.1 KiB
C

/*
* Copyright (C) 2008 Red Hat, Inc., Jason Baron <jbaron@redhat.com>
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define DYNAMIC_DEBUG_HASH_BITS 6
static const char *program;
static void usage(void)
{
printf("Usage: %s <djb2|r5> <modname>\n", program);
exit(1);
}
/* djb2 hashing algorithm by Dan Bernstein. From:
* http://www.cse.yorku.ca/~oz/hash.html
*/
unsigned int djb2_hash(char *str)
{
unsigned long hash = 5381;
int c;
c = *str;
while (c) {
hash = ((hash << 5) + hash) + c;
c = *++str;
}
return (unsigned int)(hash & ((1 << DYNAMIC_DEBUG_HASH_BITS) - 1));
}
unsigned int r5_hash(char *str)
{
unsigned long hash = 0;
int c;
c = *str;
while (c) {
hash = (hash + (c << 4) + (c >> 4)) * 11;
c = *++str;
}
return (unsigned int)(hash & ((1 << DYNAMIC_DEBUG_HASH_BITS) - 1));
}
int main(int argc, char *argv[])
{
program = argv[0];
if (argc != 3)
usage();
if (!strcmp(argv[1], "djb2"))
printf("%d\n", djb2_hash(argv[2]));
else if (!strcmp(argv[1], "r5"))
printf("%d\n", r5_hash(argv[2]));
else
usage();
exit(0);
}