Re: [PATCH 1/1] nl80211: add NL80211_CMD_GET_TSF

[Johannes Berg <johannes@sipsolutions.net>]

On Mon, 2015-02-23 at 23:38 +0800, Rohan Joyce wrote:
> Hi,
> 
> The motivation for this patch is to assist using a WiiU Gamepad with Linux. 
> The WiiU Gamepad is an input device that also contains an LCD touchscreen,
> speakers and a variety of sensors. The Gamepad connects to an access
> point (usually the WiiU console itself, but it can be coerced to connect
> to a properly configured hostap). The Gamepad provides five services over
> UDP. Two of the services that are provided (audio and video streaming to
> the device) use the TSF as a timestamp in the application layer. The
> firmware on the Gamepad checks to make sure that incoming packets for
> these services have timestamps within 1000us of its own internal clock,
> which is synced to the TSF of the access point.

Oh, right, I remember now.

> At the moment, users who want to use this device have to manually apply 
> a kernel patch similar to that which was first posted to this list a year
> ago. This patch is my attempt to implement the functionality using a more
> conventional API and make it easier for end users.
> 
> Should I include protocol implementation details specific to this device in
> the documentation of the NL80211_CMD_GET_TSF command?

Not necessarily, but some information about why this is needed would be
good.

I guess since this has no way of using something like 11v this really is
the only chance.

Note that you'll need to add a feature capability flag for this - many
drivers, even ones based on mac80211, will not be able to implement this
properly so relying only on the presence of the callback will not work
properly.

johannes