From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 291D6C282DD for ; Fri, 24 May 2019 03:05:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E98F7217D9 for ; Fri, 24 May 2019 03:05:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387615AbfEXDFT (ORCPT ); Thu, 23 May 2019 23:05:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:38642 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387434AbfEXDFT (ORCPT ); Thu, 23 May 2019 23:05:19 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2B18B205ED; Fri, 24 May 2019 03:05:17 +0000 (UTC) Date: Thu, 23 May 2019 23:05:15 -0400 From: Steven Rostedt To: Felipe Balbi Cc: Ingo Molnar , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Divya Indi Subject: Re: [RFC] Allowing modules to control tracing subsystem Message-ID: <20190523230515.01c5f58a@oasis.local.home> In-Reply-To: <87k1gdezb4.fsf@linux.intel.com> References: <87h8bvffth.fsf@linux.intel.com> <87k1gdezb4.fsf@linux.intel.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, 02 Apr 2019 08:44:31 +0300 Felipe Balbi wrote: > Hi, > > Felipe Balbi writes: Hi Felipe, I somehow missed both your original email and this gentle reminder. > > Hi guys, > > > > I've been thinking about turning my f-trace.c USB function [1] into an > > implementation of the USB Debug Class [2]. In order to support all > > requests, I would need means to control parts of the tracing subsystem, > > for example enabling and disabling tracing, flushing the trace buffer, > > changing trace buffer size, choose which trace events to enable, etc. I believe a lot of these are already available. Also note, that Divya made it possible to have your own tracing instance for a module. > > > > Some of those functions (e.g. print_trace_line()) are available for > > things like trace_kdb.c [3], but they're not available for modules; > > i.e. they're not exported symbols. > > > > This will involve a rather large change to tracing subsystem however we > > could rely on such infrastructure for remote debugging of e.g. IVIs, > > phones, etc. > > > > The USB Debug Class already predicts the presence of JTAG access and > > Hardware tracing modules to be exported over USB. It also allows for > > GDB-type access. Adding our linux kernel tracing would make it into a > > complete tracing solution. > > > > In order to fully support this we would need, not only to expose some > > internal trace functions for modules, but I suppose the trace format > > would have to be slightly better defined so that it be decoded remotely > > give access to vmlinux. > > > > What do you guys think about this? Would this be something that folks > > would be interested in? Currently we can only export ftrace data, not > > trace events or anything else. Ideally we would export raw trace buffer > > entries to be decoded at a later moment. > > Let me know what changes are needed and we can work something out. Sorry for the delay, it appears I missed quite a bit of emails in this period :-/ -- Steve > > cheers > > > > [1] https://marc.info/?i=20190321094748.7031-1-felipe.balbi@linux.intel.com > > [2] https://www.usb.org/sites/default/files/documents/usb_debug_class_rev_1_0_final_0.pdf > > [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/trace/trace_kdb.c#n20 > > A gentle reminder here. >