I'm currently looking into kernel source code of WiFI (net/mac80211) (of Samsung's Galaxy S3---GT-I9300---kernel)
And I've seen the code like below:
/*
* Scanning implementation
*
* Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
* Copyright 2004, Instant802 Networks, Inc.
* Copyright 2005, Devicescape Software, Inc.
* Copyright 2006-2007 Jiri Benc <jbenc@suse.cz>
* Copyright 2007, Michael Wu <flamingice@sourmilk.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/if_arp.h>
#include <linux/rtnetlink.h>
#include <linux/pm_qos_params.h>
#include <net/sch_generic.h>
#include <linux/slab.h>
#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "driver-ops.h"
#include "mesh.h"
#define IEEE80211_PROBE_DELAY (HZ / 33)
#define IEEE80211_CHANNEL_TIME (HZ / 33)
#define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 8)
At the bottom of the code, it defines PROBE_DELAY, CHANNEL_TIME, PASSIVE_CHANNEL_TIME with respect to variable 'HZ'
Therefore, I typed grep -r "HZ" ./ >> ~/grep_result to find where the HZ is defined.
But , as a result, there's no definition, declaration of HZ.
Where can I find exact value of HZ ?
And if I find HZ value, what is the unit measure?
HZ is typically defined to be CONFIG_HZ. CONFIG_HZ is defined during the make config process
The generic definition is in
include/asm-generic/param.h;
The architecture specific definitions are in
arch//include/asm/param.h
which tends to simply define it to be CONFIG_HZ as well; note that you may find some hard-coded definitions of HZ in
arch//include/asm/uapi/param.h
These definitions of HZ are NOT used by the kernel they are user-space API interface values;
Hope this helps.