205 lines
7.1 KiB
Plaintext
205 lines
7.1 KiB
Plaintext
Linux wireless regulatory documentation
|
|
---------------------------------------
|
|
|
|
This document gives a brief review over how the Linux wireless
|
|
regulatory infrastructure works.
|
|
|
|
More up to date information can be obtained at the project's web page:
|
|
|
|
http://wireless.kernel.org/en/developers/Regulatory
|
|
|
|
Keeping regulatory domains in userspace
|
|
---------------------------------------
|
|
|
|
Due to the dynamic nature of regulatory domains we keep them
|
|
in userspace and provide a framework for userspace to upload
|
|
to the kernel one regulatory domain to be used as the central
|
|
core regulatory domain all wireless devices should adhere to.
|
|
|
|
How to get regulatory domains to the kernel
|
|
-------------------------------------------
|
|
|
|
When the regulatory domain is first set up, the kernel will request a
|
|
database file (regulatory.db) containing all the regulatory rules. It
|
|
will then use that database when it needs to look up the rules for a
|
|
given country.
|
|
|
|
How to get regulatory domains to the kernel (old CRDA solution)
|
|
---------------------------------------------------------------
|
|
|
|
Userspace gets a regulatory domain in the kernel by having
|
|
a userspace agent build it and send it via nl80211. Only
|
|
expected regulatory domains will be respected by the kernel.
|
|
|
|
A currently available userspace agent which can accomplish this
|
|
is CRDA - central regulatory domain agent. Its documented here:
|
|
|
|
http://wireless.kernel.org/en/developers/Regulatory/CRDA
|
|
|
|
Essentially the kernel will send a udev event when it knows
|
|
it needs a new regulatory domain. A udev rule can be put in place
|
|
to trigger crda to send the respective regulatory domain for a
|
|
specific ISO/IEC 3166 alpha2.
|
|
|
|
Below is an example udev rule which can be used:
|
|
|
|
# Example file, should be put in /etc/udev/rules.d/regulatory.rules
|
|
KERNEL=="regulatory*", ACTION=="change", SUBSYSTEM=="platform", RUN+="/sbin/crda"
|
|
|
|
The alpha2 is passed as an environment variable under the variable COUNTRY.
|
|
|
|
Who asks for regulatory domains?
|
|
--------------------------------
|
|
|
|
* Users
|
|
|
|
Users can use iw:
|
|
|
|
http://wireless.kernel.org/en/users/Documentation/iw
|
|
|
|
An example:
|
|
|
|
# set regulatory domain to "Costa Rica"
|
|
iw reg set CR
|
|
|
|
This will request the kernel to set the regulatory domain to
|
|
the specificied alpha2. The kernel in turn will then ask userspace
|
|
to provide a regulatory domain for the alpha2 specified by the user
|
|
by sending a uevent.
|
|
|
|
* Wireless subsystems for Country Information elements
|
|
|
|
The kernel will send a uevent to inform userspace a new
|
|
regulatory domain is required. More on this to be added
|
|
as its integration is added.
|
|
|
|
* Drivers
|
|
|
|
If drivers determine they need a specific regulatory domain
|
|
set they can inform the wireless core using regulatory_hint().
|
|
They have two options -- they either provide an alpha2 so that
|
|
crda can provide back a regulatory domain for that country or
|
|
they can build their own regulatory domain based on internal
|
|
custom knowledge so the wireless core can respect it.
|
|
|
|
*Most* drivers will rely on the first mechanism of providing a
|
|
regulatory hint with an alpha2. For these drivers there is an additional
|
|
check that can be used to ensure compliance based on custom EEPROM
|
|
regulatory data. This additional check can be used by drivers by
|
|
registering on its struct wiphy a reg_notifier() callback. This notifier
|
|
is called when the core's regulatory domain has been changed. The driver
|
|
can use this to review the changes made and also review who made them
|
|
(driver, user, country IE) and determine what to allow based on its
|
|
internal EEPROM data. Devices drivers wishing to be capable of world
|
|
roaming should use this callback. More on world roaming will be
|
|
added to this document when its support is enabled.
|
|
|
|
Device drivers who provide their own built regulatory domain
|
|
do not need a callback as the channels registered by them are
|
|
the only ones that will be allowed and therefore *additional*
|
|
channels cannot be enabled.
|
|
|
|
Example code - drivers hinting an alpha2:
|
|
------------------------------------------
|
|
|
|
This example comes from the zd1211rw device driver. You can start
|
|
by having a mapping of your device's EEPROM country/regulatory
|
|
domain value to a specific alpha2 as follows:
|
|
|
|
static struct zd_reg_alpha2_map reg_alpha2_map[] = {
|
|
{ ZD_REGDOMAIN_FCC, "US" },
|
|
{ ZD_REGDOMAIN_IC, "CA" },
|
|
{ ZD_REGDOMAIN_ETSI, "DE" }, /* Generic ETSI, use most restrictive */
|
|
{ ZD_REGDOMAIN_JAPAN, "JP" },
|
|
{ ZD_REGDOMAIN_JAPAN_ADD, "JP" },
|
|
{ ZD_REGDOMAIN_SPAIN, "ES" },
|
|
{ ZD_REGDOMAIN_FRANCE, "FR" },
|
|
|
|
Then you can define a routine to map your read EEPROM value to an alpha2,
|
|
as follows:
|
|
|
|
static int zd_reg2alpha2(u8 regdomain, char *alpha2)
|
|
{
|
|
unsigned int i;
|
|
struct zd_reg_alpha2_map *reg_map;
|
|
for (i = 0; i < ARRAY_SIZE(reg_alpha2_map); i++) {
|
|
reg_map = ®_alpha2_map[i];
|
|
if (regdomain == reg_map->reg) {
|
|
alpha2[0] = reg_map->alpha2[0];
|
|
alpha2[1] = reg_map->alpha2[1];
|
|
return 0;
|
|
}
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
Lastly, you can then hint to the core of your discovered alpha2, if a match
|
|
was found. You need to do this after you have registered your wiphy. You
|
|
are expected to do this during initialization.
|
|
|
|
r = zd_reg2alpha2(mac->regdomain, alpha2);
|
|
if (!r)
|
|
regulatory_hint(hw->wiphy, alpha2);
|
|
|
|
Example code - drivers providing a built in regulatory domain:
|
|
--------------------------------------------------------------
|
|
|
|
[NOTE: This API is not currently available, it can be added when required]
|
|
|
|
If you have regulatory information you can obtain from your
|
|
driver and you *need* to use this we let you build a regulatory domain
|
|
structure and pass it to the wireless core. To do this you should
|
|
kmalloc() a structure big enough to hold your regulatory domain
|
|
structure and you should then fill it with your data. Finally you simply
|
|
call regulatory_hint() with the regulatory domain structure in it.
|
|
|
|
Bellow is a simple example, with a regulatory domain cached using the stack.
|
|
Your implementation may vary (read EEPROM cache instead, for example).
|
|
|
|
Example cache of some regulatory domain
|
|
|
|
struct ieee80211_regdomain mydriver_jp_regdom = {
|
|
.n_reg_rules = 3,
|
|
.alpha2 = "JP",
|
|
//.alpha2 = "99", /* If I have no alpha2 to map it to */
|
|
.reg_rules = {
|
|
/* IEEE 802.11b/g, channels 1..14 */
|
|
REG_RULE(2412-10, 2484+10, 40, 6, 20, 0),
|
|
/* IEEE 802.11a, channels 34..48 */
|
|
REG_RULE(5170-10, 5240+10, 40, 6, 20,
|
|
NL80211_RRF_NO_IR),
|
|
/* IEEE 802.11a, channels 52..64 */
|
|
REG_RULE(5260-10, 5320+10, 40, 6, 20,
|
|
NL80211_RRF_NO_IR|
|
|
NL80211_RRF_DFS),
|
|
}
|
|
};
|
|
|
|
Then in some part of your code after your wiphy has been registered:
|
|
|
|
struct ieee80211_regdomain *rd;
|
|
int size_of_regd;
|
|
int num_rules = mydriver_jp_regdom.n_reg_rules;
|
|
unsigned int i;
|
|
|
|
size_of_regd = sizeof(struct ieee80211_regdomain) +
|
|
(num_rules * sizeof(struct ieee80211_reg_rule));
|
|
|
|
rd = kzalloc(size_of_regd, GFP_KERNEL);
|
|
if (!rd)
|
|
return -ENOMEM;
|
|
|
|
memcpy(rd, &mydriver_jp_regdom, sizeof(struct ieee80211_regdomain));
|
|
|
|
for (i=0; i < num_rules; i++)
|
|
memcpy(&rd->reg_rules[i],
|
|
&mydriver_jp_regdom.reg_rules[i],
|
|
sizeof(struct ieee80211_reg_rule));
|
|
regulatory_struct_hint(rd);
|
|
|
|
Statically compiled regulatory database
|
|
---------------------------------------
|
|
|
|
When a database should be fixed into the kernel, it can be provided as a
|
|
firmware file at build time that is then linked into the kernel.
|