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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 ED585C43381 for ; Tue, 2 Apr 2019 06:33:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BE315206B7 for ; Tue, 2 Apr 2019 06:33:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554186814; bh=9Jauwe6LBIRbSkyaJXI1HzD8l3RvN+3eXZbv3mUd/i0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=mr1FtaOKsRoI4mHeNeZqON/78L19KkjannGD6jnUt1fk/M0lV0+vfROFXTsuBFYlZ YcyX10ewFPJCQCdsLUcK5+3GI9p22n/LnseDRSvYn63ozUXsAIQ1wSP4s4Bc60wgEF NywTBDrkISGpS81dasCf2MyzTYpnSxPoG2c9G/BM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729381AbfDBGdd (ORCPT ); Tue, 2 Apr 2019 02:33:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:33596 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728359AbfDBGdc (ORCPT ); Tue, 2 Apr 2019 02:33:32 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 6AFD62084C; Tue, 2 Apr 2019 06:33:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554186811; bh=9Jauwe6LBIRbSkyaJXI1HzD8l3RvN+3eXZbv3mUd/i0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sdRh4+IFNGmQbYxC+RB/68QGt9ycKEfcUhqUa9Zs8lTN5tsZ/Vs5EJ+G1ad9MpwUH FBB6Axa+Y2o34JHqxJ1WcTmBn0wgLJO2a7MCt3W1pj2Ybv83UNqpE+BD6w6K5fBO76 7b3xoRN/OLxkzoUjpKmm4KPPfoyp3Aub56AUfF64= Date: Tue, 2 Apr 2019 08:33:26 +0200 From: Greg Kroah-Hartman To: "Life is hard, and then you die" Cc: Dmitry Torokhov , Henrik Rydberg , Andy Shevchenko , Sergey Senozhatsky , Steven Rostedt , "Rafael J. Wysocki" , Lukas Wunner , Federico Lorenzi , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/4] driver core: add dev_print_hex_dump() logging function. Message-ID: <20190402063326.GB7218@kroah.com> References: <20190327014807.7472-1-ronald@innovation.ch> <20190327014807.7472-4-ronald@innovation.ch> <20190327023757.GB20766@kroah.com> <20190328002817.GF24753@innovation.ch> <20190328052917.GB18668@kroah.com> <20190328102755.GA26446@innovation.ch> <20190328112952.GA2232@kroah.com> <20190402024714.GA14213@innovation.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190402024714.GA14213@innovation.ch> User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 01, 2019 at 07:47:14PM -0700, Life is hard, and then you die wrote: > > On Thu, Mar 28, 2019 at 12:29:52PM +0100, Greg Kroah-Hartman wrote: > > On Thu, Mar 28, 2019 at 03:27:55AM -0700, Life is hard, and then you die wrote: > > > > > > On Thu, Mar 28, 2019 at 06:29:17AM +0100, Greg Kroah-Hartman wrote: > > > > On Wed, Mar 27, 2019 at 05:28:17PM -0700, Life is hard, and then you die wrote: > > > > > > > > > > On Wed, Mar 27, 2019 at 11:37:57AM +0900, Greg Kroah-Hartman wrote: > > > > > > On Tue, Mar 26, 2019 at 06:48:06PM -0700, Ronald Tschalär wrote: > > > > > > > This is the dev_xxx() analog to print_hex_dump(), using dev_printk() > > > > > > > instead of straight printk() to match other dev_xxx() logging functions. > > > > > > > --- > > > > > > > drivers/base/core.c | 43 ++++++++++++++++++++++++++++++++++++++++++ > > > > > > > include/linux/device.h | 15 +++++++++++++++ > > > > > > > 2 files changed, 58 insertions(+) > [snip] > > > > > > Anyway, no, please do not do this. Please do not dump large hex values > > > > > > like this to the kernel log, it does not help anyone. > > > > > > > > > > > > You can do this while debugging, sure, but not for "real" kernel code. > > > > > > > > > > As used by this driver, it is definitely called for debugging only and > > > > > must be explicitly enabled via a module param. But having the ability > > > > > for folks to easily generate and print out debugging info has proven > > > > > quite valuable. > > > > > > > > We have dynamic debugging, no need for module parameters at all. This > > > > isn't the 1990's anymore :) > > > > > > I am aware of dynamic debugging, but there are several issues with it > > > from the perspective of the logging I'm doing here (I mentioned these > > > in response to an earlier review already): > > > > > > 1. Dynamic debugging can't be enabled at a function or line level on > > > the kernel command line, so this means that to debug issues > > > during boot you have to enable everything, which can be way too > > > verbose > > > > You can, and should enable it at a function or line level by writing to > > the proper kernel file in debugfs. > > > > You have read Documentation/admin-guide/dynamic-debug-howto.rst, right? > > Yes, and I've played with the parameters quite a bit. > > > No need to do anything on the command line, that's so old-school :) > > Sorry if I'm being unduly dense, but then how to enable debugging > during early boot? The only other alternative I see is modifying the > initrd, and asking folks to do that is noticeably more complicated > than having them add something to the command line in grub. So from my > perspective I find kernel params far from old-school :-) You can do dynamic debugging from the kernel command line, if your code is built into the kernel (but why would a tiny driver under testing like this, not be built into the kernel?) what specifically did not work for you? > > > 2. The expressions to enable the individual logging statements are > > > quite brittle (in particular the line-based ones) since they > > > (may) change any time the code is changed - having stable > > > commands to give to users and put in documentation (e.g. > > > "echo 0x200 > /sys/module/applespi/parameters/debug") is > > > quite valuable. > > > > > > One way to work around this would be to put every single logging > > > statement in a function of its own, thereby ensuring a stable > > > name is associated with each one. > > > > Again, read the documentation, this works today as-is. > > I have read it (we're talking about the dynamic debug docs here), but > I just don't see how it addresses this in any way. You can enable/disable logging per-function, which is what you want, right? Anyway, I'm glad tracepoints work for you, that should be all that is now needed. good luck with your driver! greg k-h