[GSOC17] Porting 802.11n and 802.11ac support to iwm(4)

[Mateusz Piotrowski]

Hello,

For the last two weeks I've been busy reading the Linux iwlwifi/mvm 
driver code.

At first, I was mostly focused on the parts in charge of transmitting 
packets. Later, however, Adrian and I came up with a more precise and 
detailed plan for improving iwm. For the following weeks I intend to 
work on the antenna setup:

 1. First, I'll review iwlwifi/mvm TX and RX antenna configuration code.
    Most importantly, I am interested in what it does forinitial setup,
    MAC context setup, PHY context setup, and TX packet setup.We need to
    get these things to work otherwise MIMO rates won't work at all.

    Currently, I am looking for PLCP-related code (like the routine that
    calculates the PLCP value to stuff in the transmit descriptor and
    see what calls it and map that out a couple levels). More details
    here [1].

 2. Once I get the idea of how things from 1. work I have to investigate
    iwlwifi and iwn to see how they assemble the MIMO version of the
    transmit PLCP as right now iwm only knows about 11abg PLCP
    configuration.

 3. Subsequently, I'll add placeholders routines for 11n methods.

 4. Then I'll make MAC and PHY contexts in firmware aware of the fact
    that they can now use 11n.

 5. Finally, I have to tell net80211 that it can now use 11n and see if
    it crashes.

As always, I put the links to the most interesting and informative 
sources here [2]. It might save you a lot of time if you're willing to 
start working on WiFi drivers while knowing very little about them.

Also, I'm taking my last exam on Wednesday, so I'll be more efficient in 
the next few weeks.

Cheers,

Mateusz Piotrowski

[1]: 
https://wiki.freebsd.org/SummerOfCode2017/Porting80211nAnd80211acToFreeBSDiwm#PLCP
[2]: https://wiki.freebsd.org/MateuszPiotrowski/Drivers/WiFi101
[Project's wiki]: 
https://wiki.freebsd.org/SummerOfCode2017/Porting80211nAnd80211acToFreeBSDiwm