linux-kernel - Re: [PATCH] usb: gadget: functions: add ftrace export over USB

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Date:   Fri, 9 Jun 2017 11:07:17 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Linux USB <linux-usb@...r.kernel.org>,
        linux-kernel@...r.kernel.org,
        Chunyan Zhang <zhang.chunyan@...aro.org>
Subject: Re: [PATCH] usb: gadget: functions: add ftrace export over USB

On Fri, 09 Jun 2017 17:05:52 +0300
Felipe Balbi <felipe.balbi@...ux.intel.com> wrote:

> Hi,
> 
> Steven Rostedt <rostedt@...dmis.org> writes:
> > On Fri,  9 Jun 2017 09:13:27 +0300
> > Felipe Balbi <felipe.balbi@...ux.intel.com> wrote:
> >  
> >> Allow for ftrace data to be exported over a USB Gadget
> >> Controller. With this, we have a potentially very fast pipe for
> >> transmitting ftrace data to a Host PC for further analysis.
> >> 
> >> Note that in order to decode the data, one needs access to kernel
> >> symbols in order to convert binary data into function names and what
> >> not.
> >>   
> >
> > Can you please explain what this is in a bit more detail. I have no
> > idea what you are trying to accomplish.  
> 
> this is just another ftrace export. Just like STM
> (drivers/hwtracing/stm/ftrace.c), but I'm making use of a USB Peripheral
> Controller that may be available.
> 
> > Also, do you mean ftrace as the internal Linux tracer (which should
> > only be called "ftrace" or sometimes "Ftrace" but not "f_trace" or
> > "FTrace", that just leads to more confusion.  
> 
> heh, internal linux ftrace ;-) The driver name (f-trace.c) is just to
> follow the convention of USB functions being name f_*.c or f-*.c. I
> could call it f-ftrace.c, but seemed unnecessary.

OK, looking at the other files and functions in
drivers/usb/gadget/function, I see that F there is part of usb process.
OK, although it does make it somewhat confusing.

-- Steve