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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 715BCC43331 for ; Thu, 2 Apr 2020 08:35:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F0B32063A for ; Thu, 2 Apr 2020 08:35:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387705AbgDBIfD (ORCPT ); Thu, 2 Apr 2020 04:35:03 -0400 Received: from mga01.intel.com ([192.55.52.88]:57902 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729166AbgDBIfC (ORCPT ); Thu, 2 Apr 2020 04:35:02 -0400 IronPort-SDR: gN8u/DOcfz4UWHuTmfbDBBaLoAYRYMSkfRxbfQYwTjlHYOWZ60HJffAmp4tCdDcjZCqYOJPakI nD6bgDfz8Vng== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Apr 2020 01:35:02 -0700 IronPort-SDR: mMYzz6H5D5xoa4LoyAVyyzL6Hz0UJwAygbl2JSIJ7JKQ9evbNFNqZG1KRaSO52Y38Tih2SNbQ6 KXQLBlY8D9xw== X-IronPort-AV: E=Sophos;i="5.72,335,1580803200"; d="scan'208";a="423047048" Received: from assenmac-mobl1.ger.corp.intel.com (HELO localhost) ([10.249.35.117]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Apr 2020 01:34:53 -0700 From: Jani Nikula To: Sakari Ailus , Petr Mladek Cc: mchehab@kernel.org, Dave Stevenson , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, hverkuil@xs4all.nl, Sergey Senozhatsky , Steven Rostedt , laurent.pinchart@ideasonboard.com, Andy Shevchenko , linux-media@vger.kernel.org, Ville =?utf-8?B?U3lyasOkbMOk?= Subject: Re: [PATCH 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs In-Reply-To: <20200401140522.966-1-sakari.ailus@linux.intel.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20200401140522.966-1-sakari.ailus@linux.intel.com> Date: Thu, 02 Apr 2020 11:34:48 +0300 Message-ID: <87eet6mgk7.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 01 Apr 2020, 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. I'm not going to take a strong stand in one way or the other regarding the patch at hand, but I do think at some point we have to draw a line what should be included in printk formats. Arguably they should be reserved to things that are generally useful across large parts of the kernel, right? I think the more specialized you get, the more you should think about just using the plain old %s, and your own helpers. Because frankly, the kernel printk specifiers also start getting more than a little obscure. Or could we conceive of a way to make this locally extensible yet safe, letting callers use something like %{foo}, as well as providing a locally relevant function to do the conversion? BR, Jani. > > Suggested-by: Mauro Carvalho Chehab > Signed-off-by: Sakari Ailus > --- > Documentation/core-api/printk-formats.rst | 11 +++++++++ > lib/vsprintf.c | 29 +++++++++++++++++++++++ > 2 files changed, 40 insertions(+) > > diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst > index 8ebe46b1af39..b6249f513c09 100644 > --- a/Documentation/core-api/printk-formats.rst > +++ b/Documentation/core-api/printk-formats.rst > @@ -545,6 +545,17 @@ For printing netdev_features_t. > > Passed by reference. > > +V4L2 and DRM fourcc code (pixel format) > +--------------------------------------- > + > +:: > + > + %ppf > + > +Print a 4cc code used by V4L2 or DRM. > + > +Passed by reference. > + > Thanks > ====== > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index 7c488a1ce318..b39f0ac317c5 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -1721,6 +1721,32 @@ char *netdev_bits(char *buf, char *end, const void *addr, > return special_hex_number(buf, end, num, size); > } > > +static noinline_for_stack > +char *pixel_format_string(char *buf, char *end, const u32 *fourcc, > + struct printf_spec spec, const char *fmt) > +{ > + char ch[2] = { 0 }; > + 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); > + buf = string(buf, end, ch, spec); > + } > + > + if (*fourcc & BIT(31)) > + buf = string(buf, end, "-BE", spec); > + > + return buf; > + default: > + return error_string(buf, end, "(%pp?)", spec); > + } > +} > + > static noinline_for_stack > char *address_val(char *buf, char *end, const void *addr, > struct printf_spec spec, const char *fmt) > @@ -2131,6 +2157,7 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode, > * correctness of the format string and va_list arguments. > * - 'K' For a kernel pointer that should be hidden from unprivileged users > * - 'NF' For a netdev_features_t > + * - 'pf' V4L2 or DRM pixel format. > * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with > * a certain separator (' ' by default): > * C colon > @@ -2223,6 +2250,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, > return restricted_pointer(buf, end, ptr, spec); > case 'N': > return netdev_bits(buf, end, ptr, spec, fmt); > + case 'p': > + return pixel_format_string(buf, end, ptr, spec, fmt); > case 'a': > return address_val(buf, end, ptr, spec, fmt); > case 'd': -- Jani Nikula, Intel Open Source Graphics Center