Re: [RFC] How to store HT (40MHz) support

["Luis R. Rodriguez" <mcgrof@gmail.com>]

2010/1/21 Rafał Miłecki <zajec5@gmail.com>:
> W dniu 20 stycznia 2010 11:18 użytkownik Johannes Berg
> <johannes@sipsolutions.net> napisał:
>> On Wed, 2010-01-20 at 01:06 +0100, Rafał Miłecki wrote:
>>> +             phy->use_40mhz = conf_is_ht(conf);
>>
>> This is wrong, conf_is_ht might also be 20mhz, look at the other
>> helpers.
>
> I tried to understand what actually is HT and after reading many
> articles I have more knowledge but still I'm not 100% sure.
>
> AFAIU:
> 1) HT means using more than 1 stream in channel (and can be on any:
> 20MHz or 40MHz)

No, you can have single stream HT devices.

> 2) conf_is_ht(...) checks if mac80211 want us to use more than 1
> stream in channel

No, conf_is_ht() tells you whether or not the current device
configuration is set up to be on HT configuration.

> 3) conf_is_ht40_minus(...) checks if we should use frequency below
> current as additional 20MHz, so for example for channel 7 which is
> 2,431->2,453 we should use additinal 20MHz in channel 3 which is
> 2,411->2,433

Right it just means the secondary channel is on the lower part of the
primary, ht40_plus means its above.

> 4) conf_is_ht40_plus(...) checks if we should use frequency over
> current as additional 20MHz, so for example for channel 3 which is
> 2,411->2,433 we should use additinal 20MHz in channel 7 which is
> 2,431->2,453
>
> Is that correct?

Almost, may want to read this:

http://wireless.kernel.org/en/developers/Documentation/ieee80211/802.11n

I hope that helps.

  Luis