Re: [Linuxptp-users] Adding software-transmit (SOF_TIMESTAMPING_TX_SOFTWARE) capability to driver

[Miroslav L. <mli...@re...>]

On Tue, Jul 19, 2022 at 09:02:37PM -0700, Richard Cochran wrote:
> > I am not sure how accurate a software timestamp for a wifi device would
> > be, given the potential delay between timestamp and actual transmission.
> 
> WiFi on Linux is never going to support PTP.  The issue is the closed
> source radio firmware.  End of story.

I tested driver TX timestamping in the mt76 driver, where the firmware
is supposed to be very simple, but IIRC it didn't make a noticeable
difference when compared to user-space TX timestamping.

But if there is demand, I think we could see wireless chips with
HW-timestamping support in future. If the stations can hear each
other, maybe it wouldn't even be necessary for the access point to
support PTP, like when using a cheap Ethernet hub instead of expensive
switch with PTP support.

-- 
Miroslav Lichvar