Re: [PATCH v3 3/4] driver core: add dev_print_hex_dump() logging function.

[Steven Rostedt]

On Thu, 28 Mar 2019 12:29:52 +0100
Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:

> >   3. In at least two places we log different types of packets in the
> >      same lines of code (protected by a "if (log_mask & PKT_TYPE)") -
> >      dynamic-debug would only allow enabling or disabling logging of
> >      all packets. This could be worked around by creating a separate
> >      (but essentially duplicate) logging function for each packet type
> >      and some lookup table to call the appropriate one. Not very
> >      pretty IMO, though.  
> 
> True, but you can use tracepoints as well, that would probably be much
> easier when you are logging data streams.  You can also use an ebpf
> program with the tracepoints to log just what you need/want to when you
> want to as well.

And tracepoints have filters where you don't even need ebpf to do such
filtering.

See Documentation/trace/events.rst Section 5: Event Filtering

-- Steve