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Old 04-03-2015, 08:31 PM   #1
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Hi All, I am new in Linux

HI, this is melvin, new in linux, and keep learning in here.

we just have a project need to disable the 5GHz channel in the AR9462 due to the Approval issue.
We use "iw" to do the checking and found out the current EEPROM setting is 0x6c which enabled the 5GHz channel in passive and beacon scanning mode and caused the problem in the test lab for project~.
By the way, Is there anyone could help to advise how we could disable the 5GHz channel in the ath9k? we only need 2.4GHz only but chosen this dual band card for the project, so can't be changing.
Please help.

Last edited by elecomes; 04-03-2015 at 08:34 PM.
Old 04-04-2015, 03:19 AM   #2
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EEPROM world regulatory domain

Atheros EEPROM can use 12 custom world regulatory domains:

WOR0_WORLD = 0x60
WOR1_WORLD = 0x61
WOR2_WORLD = 0x62
WOR3_WORLD = 0x63
WOR4_WORLD = 0x64
WOR5_ETSIC = 0x65
WOR01_WORLD = 0x66
WOR02_WORLD = 0x67
EU1_WORLD = 0x68
WOR9_WORLD = 0x69
WORC_WORLD = 0x6C 0x60, 0x61, 0x62, 0x66, 0x67, 0x68 are only used today moving forward for 2.4 GHz-only band cards.

5 GHz with world regulatory domain and beacon hints

All Atheros custom world regulatory domains have all 5 GHz channels marked with a passive scan flags. The non-DFS channels can have their passive scan flags lifted through a feature implemented in cfg80211 called beacon hints. For details on that please read the beacon hints documentation.
Beacon hints

cfg80211 has a feature called beacon hinting to assist cfg80211 in allowing a card to lift passive-scan and no-beaconing flags. Passive-scan flags are used on channels to ensure that an interface will not issue a probe request out. The no-ir flag exists to allow regulatory domain definitions to disallow a device from initiating radiation of any kind and that includes using beacons, so for example AP/IBSS/Mesh/GO interfaces would not be able to initiate communication on these channels unless the channel does not have this flag. If either of these flags are present on a channel a device is prohibited from initiating communication on cfg80211.

Old regulatory rule flags like passive-scan and no-beaconing were originally invented to help with World Roaming, these two are now combined into the one and only no-ir, for no-initiating-radiation. If you do not know what country you are in you can still behave as an 802.11 STA interface but can wait to enable active scans until you see a beacon from an AP, if the channel being used is not a DFS channel and not channels 12-14 on the 2.4 GHz band. The same can be said for initiating communication, so both the old passive-scan and no-beaconing, now consolidated in modern kernels as one flag no-ir can be lifted if an AP is found beaconing on a non-DFS channel and if the channel is also not channels 12-14 on the 2.4 GHz band. cfg80211 takes advantage of this bit of logic to lift both of these flags if and only if the wiphy device is world roaming.

It is also important to note that the Linux kernel beacon hint mechanism only trusts beacons from 802.11 APs, not Mesh or IBSS. Specifically, the Linux kernel beacon hint mechanism ensures that the beacon ESS capability is set:
As I read the above, your device should not be using 5GHz channels unless there is an AP beaconing the availability of a 5GHz channel.

Last edited by allend; 04-04-2015 at 03:23 AM.
Old 04-17-2015, 08:45 AM   #3
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Hi We are using a very old kernel 3.10.55 which do not have any change after the country code setting implemented. So we are seeking a way to change the driver and disable the 5GHz.
I could see there is a patch files mentioning it

and also the latest kernel 3.19 and 4.0 implemented it into the ath9k driver, but I still can't figure out how to use it??
Anyone can help?




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