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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 E1084C43331 for ; Thu, 2 Apr 2020 07:32:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC9132064A for ; Thu, 2 Apr 2020 07:32:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387551AbgDBHcc (ORCPT ); Thu, 2 Apr 2020 03:32:32 -0400 Received: from mga14.intel.com ([192.55.52.115]:54283 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387516AbgDBHcc (ORCPT ); Thu, 2 Apr 2020 03:32:32 -0400 IronPort-SDR: KjlCnnBbhacVC+Qu+49V5qs1h8bUOGYC2gJzjS3jZOmIzynutONt/3J/kquBAvp6Zyf7zcJNgL VzBno0pFAfbw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Apr 2020 00:32:31 -0700 IronPort-SDR: gdOzEhnqEgsoR8sAYDzfV05CATH4fzVWWsS+k0boW8O/yu3Xfi3sJxeG235iqhxdcOZT0BRZiL Wb4kADP/oc4Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,334,1580803200"; d="scan'208";a="328729980" Received: from tronach-mobl1.ger.corp.intel.com (HELO kekkonen.fi.intel.com) ([10.252.38.191]) by orsmga001.jf.intel.com with ESMTP; 02 Apr 2020 00:32:28 -0700 Received: by kekkonen.fi.intel.com (Postfix, from userid 1000) id E279321F19; Thu, 2 Apr 2020 10:32:20 +0300 (EEST) Date: Thu, 2 Apr 2020 10:32:20 +0300 From: Sakari Ailus To: Andy Shevchenko Cc: Hans Verkuil , Petr Mladek , linux-media@vger.kernel.org, Dave Stevenson , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, laurent.pinchart@ideasonboard.com, mchehab@kernel.org, Sergey Senozhatsky , Steven Rostedt Subject: Re: [PATCH 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs Message-ID: <20200402073220.GB1522@kekkonen.localdomain> References: <20200401140522.966-1-sakari.ailus@linux.intel.com> <080ddddf-717e-61dc-8522-fbdbe52da94a@xs4all.nl> <20200401151332.GU1922688@smile.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200401151332.GU1922688@smile.fi.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andy, Thanks for the review. On Wed, Apr 01, 2020 at 06:13:32PM +0300, Andy Shevchenko wrote: > On Wed, Apr 01, 2020 at 04:13:51PM +0200, Hans Verkuil wrote: > > On 4/1/20 4:05 PM, Sakari Ailus wrote: > > > Add a printk modifier %ppf (for pixel format) for printing V4L2 and DRM > > > pixel formats denoted by 4ccs. The 4cc encoding is the same for both so > > > the same implementation can be used. > > %p4cc ? Sounds good. Numbers have special handling but AFAIR only right after % sign, so this should be possible. > > > > + char ch[2] = { 0 }; > > > > This can just be '{ };' > > The latter is GCC extension, while above is C standard. Former is slightly > better I think. Though see below. > > > > + unsigned int i; > > > + > > > + if (check_pointer(&buf, end, fourcc, spec)) > > > + return buf; > > > + > > > + switch (fmt[1]) { > > > + case 'f': > > > > + for (i = 0; i < sizeof(*fourcc); i++) { > > > + ch[0] = *fourcc >> (i << 3); > > > > You need to AND with 0x7f, otherwise a big endian fourcc (bit 31 is set) > > will look wrong. Also, each character is standard 7 bit ascii, bit 7 isn't > > used except to indicate a BE variant. > > Why not to do it once by a flag and do reset it once? > > u32 tmp = *fourcc; > bool be4cc = tmp & BIT(31); > > tmp &= BIT(31); I had two extra temporary variables in a version I didn't send but I figured they could be removed. :-) > > On top of that, as promised above, why not simple do it in a simpler way, i.e. > using standard idiom: > > for (i = 0; i < sizeof(*fourcc); i++) { > if (buf < end) > *buf = tmp >> (i * 8); > buf++; > } > ? I guess that's at least more efficient, and comparing buf to end is trivial. I'll do that in v2. > > > > + buf = string(buf, end, ch, spec); > > > + } > > > + > > > + if (*fourcc & BIT(31)) > > > + buf = string(buf, end, "-BE", spec); > > Another possibility > > u8 ch[8]; > > if (*fourcc & BIT(31)) { > put_unaligned_be32(tmp, &ch[0]); > strcpy(&ch[4], "-BE"); > } else { > put_unaligned_le32(tmp, &ch[0]); > strcpy(&ch[4], "-LE"); > } > return string(buf, end, &ch[0], spec); I think I prefer the loop. I figured you can only call string once, otherwise field width handling will be broken. Let's see. > > > > + return buf; > > > + default: > > > + return error_string(buf, end, "(%pp?)", spec); > > > + } > > > +} > -- Kind regards, Sakari Ailus