I am also in the process of trying to compile a kernel module ath9k.
I also receive the error
drivers/net/wireless/ath/ath9k/init.c: In function ‘ath9k_init_txpower_limits’:
drivers/net/wireless/ath/ath9k/init.c:627:26: error: ‘struct ath_common’ has no member named ‘tx_chainmask’
ah->txchainmask = common->tx_chainmask;
When attempting to enable
<*> Atheros Wireless Cards --->
<m> Atheros 802.11n wireless cards support (NEW)
<M> Atheros 802.11n wireless cards [*] Atheros ath9k AHB bus [*] Atheros ath9k [*] Atheros DFS support for certified [*] Atheros MAC statistics
[ ] Atheros ath9k rate control (NEW)
I have no idea whats up but i will peck away at it and see what happens. It is nice to know others are working on this as well.
I have a feeling it could be a required other driver or library that we are missing or failing to enable in menuconfig but i have no idea how legitimate an idea this is.