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

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Message-ID: <878tl1qmrj.fsf@linux.intel.com>
Date:   Fri, 09 Jun 2017 17:05:52 +0300
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     Steven Rostedt <rostedt@...dmis.org>
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


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.

> Or is this to do with http://www.ftrace.com/en/gb, a way to trace
> produce ;-)

heh :-) unlikely

-- 
balbi

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