3b377ea9d4
This patch provides infrastructure for machine translation of the regulatory rules database used by CRDA into a C data structure. It includes code for searching that database as an alternative to dynamic regulatory rules updates via CRDA. Most people should use CRDA instead of this infrastructure, but it provides a better alternative than the WIRELESS_OLD_REGULATORY infrastructure (which can now be removed). Signed-off-by: John W. Linville <linville@tuxdriver.com>
214 lines
7.7 KiB
Text
214 lines
7.7 KiB
Text
Linux wireless regulatory documentation
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---------------------------------------
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This document gives a brief review over how the Linux wireless
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regulatory infrastructure works.
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More up to date information can be obtained at the project's web page:
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http://wireless.kernel.org/en/developers/Regulatory
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Keeping regulatory domains in userspace
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---------------------------------------
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Due to the dynamic nature of regulatory domains we keep them
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in userspace and provide a framework for userspace to upload
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to the kernel one regulatory domain to be used as the central
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core regulatory domain all wireless devices should adhere to.
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How to get regulatory domains to the kernel
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-------------------------------------------
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Userspace gets a regulatory domain in the kernel by having
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a userspace agent build it and send it via nl80211. Only
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expected regulatory domains will be respected by the kernel.
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A currently available userspace agent which can accomplish this
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is CRDA - central regulatory domain agent. Its documented here:
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http://wireless.kernel.org/en/developers/Regulatory/CRDA
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Essentially the kernel will send a udev event when it knows
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it needs a new regulatory domain. A udev rule can be put in place
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to trigger crda to send the respective regulatory domain for a
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specific ISO/IEC 3166 alpha2.
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Below is an example udev rule which can be used:
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# Example file, should be put in /etc/udev/rules.d/regulatory.rules
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KERNEL=="regulatory*", ACTION=="change", SUBSYSTEM=="platform", RUN+="/sbin/crda"
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The alpha2 is passed as an environment variable under the variable COUNTRY.
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Who asks for regulatory domains?
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--------------------------------
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* Users
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Users can use iw:
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http://wireless.kernel.org/en/users/Documentation/iw
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An example:
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# set regulatory domain to "Costa Rica"
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iw reg set CR
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This will request the kernel to set the regulatory domain to
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the specificied alpha2. The kernel in turn will then ask userspace
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to provide a regulatory domain for the alpha2 specified by the user
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by sending a uevent.
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* Wireless subsystems for Country Information elements
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The kernel will send a uevent to inform userspace a new
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regulatory domain is required. More on this to be added
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as its integration is added.
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* Drivers
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If drivers determine they need a specific regulatory domain
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set they can inform the wireless core using regulatory_hint().
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They have two options -- they either provide an alpha2 so that
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crda can provide back a regulatory domain for that country or
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they can build their own regulatory domain based on internal
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custom knowledge so the wireless core can respect it.
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*Most* drivers will rely on the first mechanism of providing a
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regulatory hint with an alpha2. For these drivers there is an additional
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check that can be used to ensure compliance based on custom EEPROM
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regulatory data. This additional check can be used by drivers by
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registering on its struct wiphy a reg_notifier() callback. This notifier
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is called when the core's regulatory domain has been changed. The driver
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can use this to review the changes made and also review who made them
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(driver, user, country IE) and determine what to allow based on its
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internal EEPROM data. Devices drivers wishing to be capable of world
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roaming should use this callback. More on world roaming will be
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added to this document when its support is enabled.
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Device drivers who provide their own built regulatory domain
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do not need a callback as the channels registered by them are
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the only ones that will be allowed and therefore *additional*
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channels cannot be enabled.
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Example code - drivers hinting an alpha2:
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------------------------------------------
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This example comes from the zd1211rw device driver. You can start
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by having a mapping of your device's EEPROM country/regulatory
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domain value to a specific alpha2 as follows:
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static struct zd_reg_alpha2_map reg_alpha2_map[] = {
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{ ZD_REGDOMAIN_FCC, "US" },
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{ ZD_REGDOMAIN_IC, "CA" },
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{ ZD_REGDOMAIN_ETSI, "DE" }, /* Generic ETSI, use most restrictive */
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{ ZD_REGDOMAIN_JAPAN, "JP" },
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{ ZD_REGDOMAIN_JAPAN_ADD, "JP" },
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{ ZD_REGDOMAIN_SPAIN, "ES" },
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{ ZD_REGDOMAIN_FRANCE, "FR" },
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Then you can define a routine to map your read EEPROM value to an alpha2,
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as follows:
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static int zd_reg2alpha2(u8 regdomain, char *alpha2)
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{
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unsigned int i;
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struct zd_reg_alpha2_map *reg_map;
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for (i = 0; i < ARRAY_SIZE(reg_alpha2_map); i++) {
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reg_map = ®_alpha2_map[i];
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if (regdomain == reg_map->reg) {
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alpha2[0] = reg_map->alpha2[0];
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alpha2[1] = reg_map->alpha2[1];
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return 0;
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}
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}
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return 1;
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}
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Lastly, you can then hint to the core of your discovered alpha2, if a match
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was found. You need to do this after you have registered your wiphy. You
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are expected to do this during initialization.
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r = zd_reg2alpha2(mac->regdomain, alpha2);
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if (!r)
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regulatory_hint(hw->wiphy, alpha2);
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Example code - drivers providing a built in regulatory domain:
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--------------------------------------------------------------
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[NOTE: This API is not currently available, it can be added when required]
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If you have regulatory information you can obtain from your
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driver and you *need* to use this we let you build a regulatory domain
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structure and pass it to the wireless core. To do this you should
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kmalloc() a structure big enough to hold your regulatory domain
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structure and you should then fill it with your data. Finally you simply
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call regulatory_hint() with the regulatory domain structure in it.
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Bellow is a simple example, with a regulatory domain cached using the stack.
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Your implementation may vary (read EEPROM cache instead, for example).
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Example cache of some regulatory domain
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struct ieee80211_regdomain mydriver_jp_regdom = {
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.n_reg_rules = 3,
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.alpha2 = "JP",
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//.alpha2 = "99", /* If I have no alpha2 to map it to */
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.reg_rules = {
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/* IEEE 802.11b/g, channels 1..14 */
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REG_RULE(2412-20, 2484+20, 40, 6, 20, 0),
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/* IEEE 802.11a, channels 34..48 */
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REG_RULE(5170-20, 5240+20, 40, 6, 20,
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NL80211_RRF_PASSIVE_SCAN),
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/* IEEE 802.11a, channels 52..64 */
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REG_RULE(5260-20, 5320+20, 40, 6, 20,
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NL80211_RRF_NO_IBSS |
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NL80211_RRF_DFS),
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}
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};
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Then in some part of your code after your wiphy has been registered:
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struct ieee80211_regdomain *rd;
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int size_of_regd;
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int num_rules = mydriver_jp_regdom.n_reg_rules;
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unsigned int i;
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size_of_regd = sizeof(struct ieee80211_regdomain) +
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(num_rules * sizeof(struct ieee80211_reg_rule));
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rd = kzalloc(size_of_regd, GFP_KERNEL);
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if (!rd)
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return -ENOMEM;
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memcpy(rd, &mydriver_jp_regdom, sizeof(struct ieee80211_regdomain));
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for (i=0; i < num_rules; i++)
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memcpy(&rd->reg_rules[i],
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&mydriver_jp_regdom.reg_rules[i],
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sizeof(struct ieee80211_reg_rule));
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regulatory_struct_hint(rd);
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Statically compiled regulatory database
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---------------------------------------
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In most situations the userland solution using CRDA as described
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above is the preferred solution. However in some cases a set of
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rules built into the kernel itself may be desirable. To account
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for this situation, a configuration option has been provided
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(i.e. CONFIG_CFG80211_INTERNAL_REGDB). With this option enabled,
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the wireless database information contained in net/wireless/db.txt is
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used to generate a data structure encoded in net/wireless/regdb.c.
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That option also enables code in net/wireless/reg.c which queries
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the data in regdb.c as an alternative to using CRDA.
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The file net/wireless/db.txt should be kept up-to-date with the db.txt
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file available in the git repository here:
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git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-regdb.git
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Again, most users in most situations should be using the CRDA package
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provided with their distribution, and in most other situations users
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should be building and using CRDA on their own rather than using
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this option. If you are not absolutely sure that you should be using
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CONFIG_CFG80211_INTERNAL_REGDB then _DO_NOT_USE_IT_.
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