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diff --git a/Documentation/networking/regulatory.rst b/Documentation/networking/regulatory.rst new file mode 100644 index 000000000..16782a95b --- /dev/null +++ b/Documentation/networking/regulatory.rst @@ -0,0 +1,209 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================================= +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: + +https://wireless.wiki.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: + +https://wireless.wiki.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: + +https://wireless.wiki.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. |