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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,194 @@ | ||
| Linux wireless regulatory documentation | ||
| --------------------------------------- | ||
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| This document gives a brief review over how the Linux wireless | ||
| 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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| 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. | ||
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| How to get regulatory domains to the kernel | ||
| ------------------------------------------- | ||
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| 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. | ||
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| A currently available userspace agent which can accomplish this | ||
| 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 | ||
| 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. | ||
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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 | ||
| 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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| * 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" | ||
| iw reg set CR | ||
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| 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. | ||
|
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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 | ||
| regulatory domain is required. More on this to be added | ||
| as its integration is added. | ||
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| * Drivers | ||
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| 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. | ||
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| *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. | ||
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| 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* | ||
| cannels cannot be enabled. | ||
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| Example code - drivers hinting an alpha2: | ||
| ------------------------------------------ | ||
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| 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 to a specific alpha2 as follows: | ||
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| 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" }, | ||
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| Then you can define a routine to map your read EEPROM value to an alpha2, | ||
| as follows: | ||
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| 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; | ||
| } | ||
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| 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. | ||
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| r = zd_reg2alpha2(mac->regdomain, alpha2); | ||
| if (!r) | ||
| regulatory_hint(hw->wiphy, alpha2, NULL); | ||
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| Example code - drivers providing a built in regulatory domain: | ||
| -------------------------------------------------------------- | ||
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| 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. | ||
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| Bellow is a simple example, with a regulatory domain cached using the stack. | ||
| 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 = { | ||
| .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(2412-20, 2484+20, 40, 6, 20, 0), | ||
| /* IEEE 802.11a, channels 34..48 */ | ||
| REG_RULE(5170-20, 5240+20, 40, 6, 20, | ||
| NL80211_RRF_PASSIVE_SCAN), | ||
| /* IEEE 802.11a, channels 52..64 */ | ||
| REG_RULE(5260-20, 5320+20, 40, 6, 20, | ||
| NL80211_RRF_NO_IBSS | | ||
| NL80211_RRF_DFS), | ||
| } | ||
| }; | ||
|
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| Then in some part of your code after your wiphy has been registered: | ||
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| int r; | ||
| struct ieee80211_regdomain *rd; | ||
| int size_of_regd; | ||
| int num_rules = mydriver_jp_regdom.n_reg_rules; | ||
| unsigned int i; | ||
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| size_of_regd = sizeof(struct ieee80211_regdomain) + | ||
| (num_rules * sizeof(struct ieee80211_reg_rule)); | ||
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| rd = kzalloc(size_of_regd, GFP_KERNEL); | ||
| if (!rd) | ||
| 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++) { | ||
| memcpy(&rd->reg_rules[i], &mydriver_jp_regdom.reg_rules[i], | ||
| sizeof(struct ieee80211_reg_rule)); | ||
| } | ||
| r = regulatory_hint(hw->wiphy, NULL, rd); | ||
| if (r) { | ||
| kfree(rd); | ||
| return r; | ||
| } | ||
|
|
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