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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 2CA0CC433DB for ; Fri, 12 Feb 2021 11:30:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06D9D64E01 for ; Fri, 12 Feb 2021 11:30:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230078AbhBLLa5 (ORCPT ); Fri, 12 Feb 2021 06:30:57 -0500 Received: from mga04.intel.com ([192.55.52.120]:18879 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230004AbhBLLar (ORCPT ); Fri, 12 Feb 2021 06:30:47 -0500 IronPort-SDR: yCGLZcQjAnRF3jwg+k6eCTJz/NDTrRh/48BYQPRY4vlrv/cW0aHnCs9dfncr6f4NHstjk+nm57 vd2SBd/Zcm7w== X-IronPort-AV: E=McAfee;i="6000,8403,9892"; a="179839198" X-IronPort-AV: E=Sophos;i="5.81,173,1610438400"; d="scan'208";a="179839198" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Feb 2021 03:29:01 -0800 IronPort-SDR: HUg+trz2d5paAqvWN9dd0/75YMfj8GXGjps6WWAjelEU+HN3D9b3SAzc3oppS+4yCZVsnCkfSn gf9WEc+KzwWA== X-IronPort-AV: E=Sophos;i="5.81,173,1610438400"; d="scan'208";a="587438215" Received: from paasikivi.fi.intel.com ([10.237.72.42]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Feb 2021 03:28:58 -0800 Received: from paasikivi.fi.intel.com (localhost [127.0.0.1]) by paasikivi.fi.intel.com (Postfix) with ESMTP id 9631620345; Fri, 12 Feb 2021 13:28:56 +0200 (EET) Date: Fri, 12 Feb 2021 13:28:56 +0200 From: Sakari Ailus To: Petr Mladek Cc: Andy Shevchenko , Linux Kernel Mailing List , Linux Media Mailing List , Dave Stevenson , dri-devel , Hans Verkuil , Laurent Pinchart , Mauro Carvalho Chehab , Sergey Senozhatsky , Steven Rostedt , Joe Perches , Jani Nikula , Rasmus Villemoes Subject: Re: [PATCH v6 1/3] lib/vsprintf: Add support for printing V4L2 and DRM fourccs Message-ID: <20210212112856.GE3@paasikivi.fi.intel.com> References: <20210208200903.28084-1-sakari.ailus@linux.intel.com> <20210208200903.28084-2-sakari.ailus@linux.intel.com> <20210209092032.GC32460@paasikivi.fi.intel.com> <20210209174755.GH32460@paasikivi.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Petr, Thanks for the comments. On Thu, Feb 11, 2021 at 06:14:28PM +0100, Petr Mladek wrote: > On Tue 2021-02-09 19:47:55, Sakari Ailus wrote: > > Hi Andy, > > > > On Tue, Feb 09, 2021 at 11:58:40AM +0200, Andy Shevchenko wrote: > > > On Tue, Feb 09, 2021 at 11:20:32AM +0200, Sakari Ailus wrote: > > > > On Mon, Feb 08, 2021 at 10:43:30PM +0200, Andy Shevchenko wrote: > > > > > On Mon, Feb 8, 2021 at 10:11 PM Sakari Ailus > > > > > wrote: > > > > > > ... > > > > > > > > > + %p4cc BG12 little-endian (0x32314742) > > > > > > > > > > This misses examples of the (strange) escaping cases and wiped > > > > > whitespaces to make sure everybody understands that 'D 12' will be the > > > > > same as 'D1 2' (side note: which I disagree on, perhaps something > > > > > should be added into documentation why). > > > > > > > > The spaces are expected to be at the end only. I can add such example if > > > > you like. There are no fourcc codes with spaces in the middle in neither > > > > V4L2 nor DRM, and I don't think the expectation is to have them either. > > > > > > But then the code suggests otherwise. Perhaps we need to extract > > > skip_trailing_spaces() from strim() and use it here. > > > > But this wouldn't affect the result in this case, would it? > > Is there any existing implementation that would skip spaces, please? > > IMHO, this might just hide problems. We should show exactly what > is stored unless anyone explicitly ask for skipping that spaces. I discussed this with Hans and we concluded spaces shouldn't be dropped. Spaces can be present in the codes themselves in any case. > > > > > > > ... > > > > > > > > > +static noinline_for_stack > > > > > > +char *fourcc_string(char *buf, char *end, const u32 *fourcc, > > > > > > + struct printf_spec spec, const char *fmt) > > > > > > +{ > > > > > > > > > > > + char output[sizeof("(xx)(xx)(xx)(xx) little-endian (0x01234567)")]; > > > > > > > > > > Do we have any evidence / document / standard that the above format is > > > > > what people would find good? From existing practices (I consider other > > > > > printings elsewhere and users in this series) I find '(xx)' form for > > > > > hex numbers is weird. The standard practice is to use \xHH (without > > > > > parentheses). > > > > > > > > Earlier in the review it was proposed that special handling of codes below > > > > 32 should be added, which I did. Using the parentheses is apparently an > > > > existing practice elsewhere. > > > > > > Where? \xHH is quite well established format for escaping. Never heard about > > > '(xx)' variant before this very series. > > > Mauro referred to FourCC codes while reviewing an earlier version of this, > > such as RGB(15). > > This is quite easy to parse. The problem is that it is not clear > whether it is hexa or decimal number. > > > Does \× imply only the next two characters are hexadecimal? I have to admit > > I don't remember seeting that, nor \x notation is common. > > Hmm, the /xyy format might be hard to parse. > > What about using the same approach as drm_get_format_name()? > I mean printing '?' when the character is not printable. > The exact value is printed later anyway. > > The advantage is that it will always printk 4 characters. "?" can be expanded by the shell. We (me and Hans) both though a dot (".") would be good. These aren't going to be present in valid fourcc codes in any case. > > > > > > Note that neither DRM nor V4L2 currently has such fourcc codes currently. > > > > > > ... > > > > > > > > > + p = special_hex_number(p, output + sizeof(output) - 2, *fourcc, > > > > > > + sizeof(u32)); > > > > > > > > > > This is perfectly one line (in this file we have even longer lines). > > Ailus, please do not take this as a criticism of your patch. > I understand that it might have sounded like this but Andy did > not mean it. > > Andy prefers slightly longer lines over wrapping only few characters. > It makes sense to me. There are more people with the same opinion. > Even checkpatch.pl tolerates lines up to 100 characters these days. > > Of course, this is a subsystem specific preference. You did not have > any chance to know it. There is no need to fight over it. Fair enough; I can violate the coding style a little in v7. -- Kind regards, Sakari Ailus