Re: A good way to get CSI info to user-space?

[Johannes Berg <johannes@sipsolutions.net>]

On Tue, 2017-10-24 at 06:50 -0700, Ben Greear wrote:

> > We keep having this discussion. You need to fix this, it should be
> > really simple to fix this - just remove all checks for CONF_MONITOR
> > from ath10k and make it use WANT_MONITOR_VIF instead if it doesn't
> > already.
> 
> I don't recall having this discussion, 

I'm pretty sure I had this discussion about ath10k not liking virtual
monitor, but maybe it was with somebody else.

> but even if you can do a
> non-promiscuous monitor mode, you would have to end up having a bpf
> socket filter and packet socket, right?

True.

> Wouldn't that have a noticeable effect on performance on modest sized
> AP hardware?

Yes. I was planning to add the wifi BPF to fix that:
https://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git/log/?h=bpf

You shouldn't think that building netlink messages is free though.
There's a lot more locking etc. going on there.

> > > mac80211_nl_send_opaque_event(mac80211-handle, int data-type, u8* data, int data_len);
> > 
> > I will not accept this upstream.
> 
> Thanks for letting me know up front, at least.
> 
> Anyone know if there is a useful way to stream events from debugfs
> and/or sysfs w/out having to busy-poll on it?

There's relayfs, which is kinda built for that. You could even use
netlink vendor events, but I don't really think netlink is appropriate
here.

johannes