Hi Francisco, On Mon, Mar 18, 2013 at 9:31 PM, Francisco Cuesta <ndarkness@xxxxxxxxx> wrote: > Hello iw developers, > > I would like to ask a question related to the command iw list. The > channels shown with this command where are they taken from? I mean, > does iw call the drivers' API to see which frequencies it can provide? iw calls the kernel's API (nl80211) to get a list of channels available for the device specified. > I ask this in that if I change the regulatory domain to Japan for > instance, I cannot see the 4.9GHz channels with iw list, does it mean > that the driver doesn't support such a channels or that I maybe have > to modify iw list source in order to make them show up? There is much more going on. Everything is working exactly as it should. Most wireless cards contain a small EEPROM which, amongst other things, specifies the calibration parameters and some regulatory information for that specific card. A card sold in a particular country is generally calibrated to work with the channels specified by that country's laws, and no calibration is performed for any other channels. The driver restricts the usage of that card so that it only uses the channels specified in the laws it was calibrated against. As each country has different laws relating to which channels are usable, the kernel regulatory code takes every piece of information we have, whether this is data from the card or specified by the user, and calculates a set of channels which satisfies the laws of all the countries we may be in, given the information at hand. In your case, firstly, your card is probably calibrated for a country that doesn't allow wifi on 4.9GHz channels, so when you tell the kernel that you're in Japan it calculates a set of channels that is allowed where the card is from, and is also allowed in Japan and uses that. Secondly, if I recall correctly, cards which can use the 4.9GHz channels are fairly rare, as they're only developed for the Japanese market. I hope that explains it. Thanks, -- Julian Calaby Email: julian.calaby@xxxxxxxxx Profile: http://www.google.com/profiles/julian.calaby/ .Plan: http://sites.google.com/site/juliancalaby/ -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
