netdev - Re: [PATCH] mctp i2c: Add rx trace

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Message-ID: <CAN7-cG5w9rjhJnDJJSOTiopxkj75mOJEC9eKZqmJaqbeMudPQQ@mail.gmail.com>
Date: Wed, 29 May 2024 20:01:52 +0300
From: Tal Yacobi <talycb8@...il.com>
To: Jeremy Kerr <jk@...econstruct.com.au>
Cc: matt@...econstruct.com.au, rostedt@...dmis.org, mhiramat@...nel.org, 
	mathieu.desnoyers@...icios.com, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] mctp i2c: Add rx trace

Hi Jeremy,

Thanks for the reply.

> > mctp-i2c rx implementation doesn't call
> > __i2c_transfer which calls the i2c reply trace function.
>
> No, but we can trace the i2c rx path through the trace_i2c_slave
> tracepoint. It is a little messier than tracing trace_i2c_write, but
> has been sufficient with the debugging I've needed in the past.

Oh, I missed that.
I had to test it with an older kernel without i2c_slave tracing
so I looked only at the regular i2c and mctp trace paths.

> > Add an mctp_reply trace function that will be used instead.
>
> Can you elaborate a little on what you were/are looking to inspect
> here? (mainly: which packet fields are you interested in?) That will
> help to determine the best approach here.

Sure, I basically wanted to trace the i2c packet buffer in a simple way.
Although, it seems we already have that in the trace_i2c_slave since 5.18 so
it could be redundant, unless you see any other potential use for it.

Thanks,
Tal.