Re: [PATCH] ath9k: add module option for disabling 11n functionality

[Michel Alexandre Salim <salimma@fedoraproject.org>]

On 06/29/2011 03:09 PM, Jouni Malinen wrote:
> On Wed, Jun 29, 2011 at 10:56:33AM +0200, Michel Alexandre Salim wrote:
>> I agree with you and Adrian; it should ideally be in the 802.11
>> stack. But as Ben noted, it does have a useful purpose -- for
>> debugging.
>>
>> If the maintainers are agreeable to a shared mac80211 mechanism,
>> which is the preferred way to handle this -- get this in, then
>> refactor *both* iwlagn and ath9k to use it, or to implement a shared
>> mechanism, demonstrate it with ath9k, then fix iwlagn later?
>
> I don't follow this.. Why would we get this into ath9k first if the more
> appropriate way of doing this would be to modify mac80211 in the first
> place. I see no point in doing driver specific hacks for this unless
> there really is some driver specific issues that are being worked around
> and that does not seem to be the case here.
>
The argument would be that driver-specific implementations are easier to 
get committed, and less intrusive than a general framework, but yes, I 
would prefer a more general solution myself.

> As far as being able to disable 802.11n in general is concerned, it
> would much better to do that as a parameter for the connection (e.g.,
> new nl80211 attribute for NL80211_CMD_ASSOCIATE) rather than a module
> parameter. This workaround seems to be needed with some APs and global
> disabling of 802.11n does not sound like the ideal mechanism for that.

Would this not require modifications to e.g. NetworkManager, ConnMan 
etc.  as well? While a module parameter is not an ideal workaround, it's 
at least easy to use. If this goes in as a connection parameter, it'd be 
nice to still have a way of manually adjusting it through a command-line 
tool.

My first attempt to solve this was to use 'iwconfig wlan0 set rate 54M' 
-- but this yields "Operation not supported". How about making a request 
for a rate of 54M or below switch the device to 802.11g mode (and 
optionally, a rate of 11M or below => 802.11b mode)? That way we don't 
need to invent a new interface at all. How would I go about adding 
support for rate setting requests to the driver?

Thanks,

-- 
Michel Alexandre Salim
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