netdev - Re: pull-request: wireless-next-2023-03-30

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Message-ID: <ccc046c7e7db68915447c05726dd90654a7a8ffc.camel@intel.com>
Date:   Tue, 18 Apr 2023 13:35:50 +0000
From:   "Greenman, Gregory" <gregory.greenman@...el.com>
To:     "richardcochran@...il.com" <richardcochran@...il.com>,
        "kuba@...nel.org" <kuba@...nel.org>
CC:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "johannes@...solutions.net" <johannes@...solutions.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Stern, Avraham" <avraham.stern@...el.com>
Subject: Re: pull-request: wireless-next-2023-03-30

On Wed, 2023-04-12 at 20:33 -0700, Richard Cochran wrote:
> On Tue, Apr 04, 2023 at 12:45:46AM +0200, Richard Cochran wrote:
> > On Fri, Mar 31, 2023 at 12:06:48AM -0700, Jakub Kicinski wrote:
> > > On Thu, 30 Mar 2023 22:56:11 +0200 Johannes Berg wrote:
> > > >  * hardware timestamping support for some devices/firwmares
> > > 
> > > Was Richard CCed on those patches? 
> > > Would have been good to see his acks there.
> > > 
> > > Adding him here in case he wants to take a look 'post factum'.
> > 
> > Timestamping on wifi is something I've spent a fair amount of time
> > thinking about.  I'll take a look but not this week as I am on
> > vacation until April 10.
> 
> This so-called "hardware timestamping support" appears to be a big
> nothing burger.
> 
> I took a quick look at the PR, and AFAICT this is only internal code
> for iwlwifi/mvm, and the code is dead code, meaning not reachable by
> user space for any practical purpose.
> 
> Like in drivers/net/wireless/intel/iwlwifi/mvm/ops.c ...
> 
>         RX_HANDLER_GRP(LEGACY_GROUP,
>                        WNM_80211V_TIMING_MEASUREMENT_NOTIFICATION,
>                        iwl_mvm_time_sync_msmt_event, RX_HANDLER_SYNC,
>                        struct iwl_time_msmt_notify),
>         RX_HANDLER_GRP(LEGACY_GROUP,
>                        WNM_80211V_TIMING_MEASUREMENT_CONFIRM_NOTIFICATION,
>                        iwl_mvm_time_sync_msmt_confirm_event, RX_HANDLER_SYNC,
>                        struct iwl_time_msmt_cfm_notify),
> 
> These aren't useful, or are they?
> 
> I am aware of FTM etc, but I see no attempt to do anything with it in
> this code.
> 
> Thanks,
> Richard

Just a few clarifications. These two notifications are internal to iwlwifi, sent
by the firmware to the driver. Then, the timestamps are added to the rx/tx status
via mac80211 api. Actually, we already have a functional implementation of ptp4l
over wifi using this driver support.