Adding software-transmit (SOF_TIMESTAMPING_TX_SOFTWARE) capability to driver

[Mo-az92]

Hello,

i am using Ath9k driver to implement Wifi-ptp .

the ethtool tool shows, the interface does not support neither software nor hardware timestamping.
so how can i add software-transmit (SOF_TIMESTAMPING_TX_SOFTWARE) capability to the driver?

in the README.org of linuxptp is written adding this capability entails adding a single line of code to the device driver.

where should this line of code added?

Thanks.