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

[Ben Greear <greearb@candelatech.com>]

On 10/25/2017 07:30 AM, Zefir Kurtisi wrote:
> Hi Ben,
>
> On 10/24/2017 03:55 PM, Johannes Berg wrote:
>> On Tue, 2017-10-24 at 06:50 -0700, Ben Greear wrote:
>> [...]
>>> 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.
>>
> This is what I would also suggest, alas it is not clear if the events need to be
> processed realtime.
>
> The relayfs is used to stream the spectral data from ath9k (and afaik also from
> ath10k) to userspace. Very easy to implement: kernel pushes TLVs into the relayfs,
> userspace pulls them.
>
> It is 'realtime-enough' to display realtime spectral graphs, but since you are
> reading the stream in buffer-slices, you have to wait for a slice to fill up
> before it is available at userspace (or you flush every TLV at kernel side, which
> kills efficiency).
>
> That is: if you need to immediately process events, relayfs is maybe not the right
> choice, if you can process them in bulk, that's the most efficient way to go.

The netlink vendor API seems to do exactly what I was hoping for earlier,
so I have started poking at that.

There is at least one other set of 'per-peer tx-beamforming' data that might be worth
exporting via the same mechanism.

Any particular reason why relayfs would be better than netlink?

Thanks,
Ben


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com