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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 987D3C54FD0 for ; Mon, 27 Apr 2020 16:02:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B0C7205C9 for ; Mon, 27 Apr 2020 16:02:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728500AbgD0QCj (ORCPT ); Mon, 27 Apr 2020 12:02:39 -0400 Received: from smtprelay0059.hostedemail.com ([216.40.44.59]:48288 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726539AbgD0QCj (ORCPT ); Mon, 27 Apr 2020 12:02:39 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay05.hostedemail.com (Postfix) with ESMTP id CE7BD18029587; Mon, 27 Apr 2020 16:02:37 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: ship96_33c1d1869b436 X-Filterd-Recvd-Size: 5476 Received: from XPS-9350.home (unknown [47.151.136.130]) (Authenticated sender: joe@perches.com) by omf18.hostedemail.com (Postfix) with ESMTPA; Mon, 27 Apr 2020 16:02:35 +0000 (UTC) Message-ID: <0c487ba493f4b4c0f68b3dfd23f14a080e4fb0c2.camel@perches.com> Subject: Re: [RESEND PATCH v3 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs From: Joe Perches To: Sakari Ailus , Petr Mladek Cc: Andy Shevchenko , linux-media@vger.kernel.org, Dave Stevenson , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, hverkuil@xs4all.nl, laurent.pinchart@ideasonboard.com, mchehab@kernel.org, Sergey Senozhatsky , Steven Rostedt , Jani Nikula Date: Mon, 27 Apr 2020 09:02:34 -0700 In-Reply-To: <20200427145303.29943-1-sakari.ailus@linux.intel.com> References: <20200427145303.29943-1-sakari.ailus@linux.intel.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.36.1-2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2020-04-27 at 17:53 +0300, Sakari Ailus wrote: > Add a printk modifier %p4cc (for pixel format) for printing V4L2 and DRM > pixel formats denoted by fourccs. The fourcc encoding is the same for both > so the same implementation can be used. [] > - Added WARN_ON_ONCE() sanity checks. Comments on these are welcome; I'd > expect them mostly be covered by the tests. All the WARN_ON_ONCE uses are not necessary. > diff --git a/lib/vsprintf.c b/lib/vsprintf.c [] > @@ -1721,6 +1721,89 @@ char *netdev_bits(char *buf, char *end, const void *addr, > return special_hex_number(buf, end, num, size); > } > > +static noinline_for_stack > +char *fourcc_string(char *buf, char *end, const u32 *__fourcc, > + struct printf_spec spec, const char *fmt) There's no reason to use __ prefixed argument names here. > +{ > +#define FOURCC_HEX_CHAR_STR "(xx)" > +#define FOURCC_BIG_ENDIAN_STR " big-endian" > +#define FOURCC_LITTLE_ENDIAN_STR " little-endian" I don't believe used-once macro defines are useful. > +#define FOURCC_HEX_NUMBER " (0x01234567)" > +#define FOURCC_STRING_MAX \ > + FOURCC_HEX_CHAR_STR FOURCC_HEX_CHAR_STR FOURCC_HEX_CHAR_STR \ > + FOURCC_HEX_CHAR_STR FOURCC_LITTLE_ENDIAN_STR FOURCC_HEX_NUMBER This is very difficult to read and is size dependent on the size of little-endian > big_endian I'd write it out FOURCC_STRING_MAX sizeof("(xx)(xx)(xx)(xx) little-endian (0x01234567)") and then not have the define at all but use the written out string in the declaration. > + struct printf_spec my_spec = { > + .type = FORMAT_TYPE_UINT, > + .field_width = 2, > + .flags = SMALL, > + .base = 16, > + .precision = -1, > + }; my_spec isn't usefully named, likely not necessary at all, and if really necessary, it should be static const > + char __s[sizeof(FOURCC_STRING_MAX)]; I'd declare the buffer char fourcc[sizeof("(xx)(xx)(xx)(xx) little-endian (0x01234567)"]; like all the other specialty functions do. > + char *s = __s; There's no reason to use __ prefixed variable names here either. All the other specialty function use: char *p = ; > + unsigned int i; just int i; is typical > + /* > + * The 31st bit defines the endianness of the data, so save its printing > + * for later. > + */ > + u32 fourcc = *__fourcc & ~BIT(31); bool be = fourcc & BIT(31); > + int ret; > + > + if (check_pointer(&buf, end, __fourcc, spec)) > + return buf; > + > + if (fmt[1] != 'c' || fmt[2] != 'c') > + return error_string(buf, end, "(%p4?)", spec); > + > + for (i = 0; i < sizeof(fourcc); i++, fourcc >>= 8) { > + unsigned char c = fourcc >> (i*8); Please remove the fourcc >>= 8 from the loop and use unsigned char c = fourcc >> (i*8); If I understand this correctly, I think this is simpler: if (isascii(c) && isprint(c)) { *s++ = c; } else { *s++ = '('; s = hex_byte_pack(s, c); *s++ = ')'; } > + > + /* Weed out spaces */ > + if (c == ' ') > + continue; > + > + /* Print non-control characters as-is */ > + if (c > ' ') { > + *s = c; > + s++; > + continue; > + } > + > + if (WARN_ON_ONCE(sizeof(__s) < > + (s - __s) + sizeof(FOURCC_HEX_CHAR_STR))) > + break; > + > + *s = '('; > + s++; > + s = number(s, s + 2, c, my_spec); > + *s = ')'; > + s++; > + } > + > + ret = strscpy(s, *__fourcc & BIT(31) ? FOURCC_BIG_ENDIAN_STR > + : FOURCC_LITTLE_ENDIAN_STR, > + sizeof(__s) - (s - __s)); If you size the initial buffer correctly, strscpy is unnecessary. strcpy(s, ? "big endian" : "little endian"); s += strlen(s); > + if (!WARN_ON_ONCE(ret < 0)) > + s += ret; > + > + if (!WARN_ON_ONCE(sizeof(__s) < > + (s - __s) + sizeof(FOURCC_HEX_NUMBER))) { > + *s = ' '; > + s++; > + *s = '('; > + s++; *s++ = ' '; *s++ = '('; + /* subtract parentheses and the space from the size */ > + special_hex_number(s, s + sizeof(FOURCC_HEX_NUMBER) - 3, > + *__fourcc, sizeof(u32)); > + s += sizeof(u32) * 2 + 2 /* 0x */; > + *s = ')'; > + s++; *s++ = ')'; > + *s = '\0'; > + } > + > + return string(buf, end, __s, spec); > +} >