Re: Help adding trace events to xHCI

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Johannes Berg <johannes@xxxxxxxxxxxxxxxx> writes:

>> (Mentors and wireless folks, we're struggling a bit with adding trace
>> events to the xHCI USB host controller driver.  I'm trying to look at
>> the ath6kl driver trace events as an example.  We could use some help
>> and/or advice.)
>
> Those were in turn modelled on mac80211, cfg80211 and/or iwlwifi, I
> think; might be worth also looking there. In general though, it's all
> pretty similar.

Correct, I used your code as example.

> The message tracing was really more of an after-thought in iwlwifi (and
> ath6kl as well I guess) because we already had a lot of debug messages
> and capturing it all together can be useful.
>
> However, tracing all the debug messages is actually fairly expensive, I
> think in part because of the string formatting and in part because of
> the always-max allocations in the ringbuffer.

The reason why added message tracing to ath6kl was that I wanted to
combine wpasupplicant, cfg80211 and ath6kl debug messages all into file
with synchronised timestamps. In this case I wasn't actually concerned
about performance at all.

-- 
Kalle Valo
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