From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS17314 8.43.84.0/22 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, PDS_RDNS_DYNAMIC_FP,RCVD_IN_DNSWL_MED,RDNS_DYNAMIC,SPF_HELO_PASS, SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 6C5AE1F8C6 for ; Fri, 30 Jul 2021 12:06:07 +0000 (UTC) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 7DD57386483F for ; Fri, 30 Jul 2021 12:06:06 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7DD57386483F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1627646766; bh=rix5ghm6ZbxENVsLjCegCAejOMwyvvkoNwTd3V5B72U=; h=Date:To:Subject:References:In-Reply-To:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=q7xZT2tT+4JxogCMuLFzvhXnPEK/odizzLk03nY6uZCtv8IwN1oXz+S1R2Yo70sdC G2HKuJtMiMcQKaQYdArp1EeDFSvUoNTKEv0ITIvjMdjQz9nq/Gne9EbKnckYDpoLde sCCd0eSI6NfSRHbW1CTsRS+ZaWYa77aZcBT1E0dI= Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by sourceware.org (Postfix) with ESMTPS id 272483857832 for ; Fri, 30 Jul 2021 12:05:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 272483857832 Received: by mail.kernel.org (Postfix) with ESMTPSA id ED93961050; Fri, 30 Jul 2021 12:05:44 +0000 (UTC) Received: by pali.im (Postfix) id 6A9BA772; Fri, 30 Jul 2021 14:05:42 +0200 (CEST) Date: Fri, 30 Jul 2021 14:05:42 +0200 To: "Alejandro Colomar (man-pages)" Subject: Re: [PATCH] ioctl_tty.2: Add example how to get or set baudrate on the serial port Message-ID: <20210730120542.dv62jtm6lpfmfjyx@pali> References: <20210730095333.6118-1-pali@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: NeoMutt/20180716 X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: =?utf-8?q?Pali_Roh=C3=A1r_via_Libc-alpha?= Reply-To: Pali =?utf-8?B?Um9ow6Fy?= Cc: Marek =?utf-8?B?QmVow7pu?= , "G. Branden Robinson" , libc-alpha@sourceware.org, Michael Kerrisk , linux-man@vger.kernel.org Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" Hello! On Friday 30 July 2021 13:47:06 Alejandro Colomar (man-pages) wrote: > Hi Pali, > > On 7/30/21 11:53 AM, Pali Rohár wrote: > > Signed-off-by: Pali Rohár > > Thanks for the patch! > > Please see some comments below. > > Cheers, > > Alex > > > > --- > > man2/ioctl_tty.2 | 60 ++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 60 insertions(+) > > > > diff --git a/man2/ioctl_tty.2 b/man2/ioctl_tty.2 > > index 0b0083c671a7..9d394572ae93 100644 > > --- a/man2/ioctl_tty.2 > > +++ b/man2/ioctl_tty.2 > > @@ -750,6 +750,66 @@ main(void) > > close(fd); > > } > > .EE > > +.PP > > +Get or set arbitrary baudrate on the serial port. > > +.PP > > +.EX > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > Unless there's a reason to use a specific include order (and if so, add a > comment), please use alphabetical order. Ok. Seems that alphabetical order compiles fine too. > > + > > +int > > +main(int argc, char *argv[]) > > +{ > > +#if !defined(TCGETS2) || !defined(TCSETS2) || !defined(BOTHER) > > + fprintf(stderr, "TCGETS2, TCSETS2 or BOTHER is unsupported\\n"); > > + return 1; > > +#else > > Do we want the program to compile if those are unsupported? My intention was to provide example which compiles fine on any Linux architecture and in case of error it reports it at runtime. On architectures where are TCGETS2/TCSETS2 ioctls unsupported, there are still supported TCGETS/TCSETS ioctls. So proper Linux portable program should fallback to TCGETS/TCSETS ioctls with Bnnn constants. So for example setting baudrate to 115200 would be possible via predefined constant B115200 in c_cflag member even when struct termios2 with c_ospeed is unsupported. I just did not put this fallback into this example as it would be quite loooong (as it is needed to add big switch for every Bnnn constant and convert numeric value into Bnnn) and example show how to use TCGETS2/TCSETS2 (not TCGETS/TCSETS). > Maybe you can #error there and simplify the reader having to parse the > preprocessor directive mentally: > > #if !defined... > # error ... > #endif > > I know it's non-standard, but I think it's common enough so that we can use > it here. #error is standard. It is already defined in C99 (section 6.10.5 Error directive). > > + struct termios2 tio2; > > + int fd, rc; > > + > > + if (argc != 2 && argc != 3) { > > + fprintf(stderr, "Usage: %s device [new_baudrate]\\n", argv[0]); > > We use \e for printing the escape character. Not \\ Ok! > CC: Branden > > See groff_man(7): > Portability > [...] > > Similar caveats apply to escapes. Some escape sequences > are however required for correct typesetting even in man > pages and usually do not cause portability problems: > > [...] > > \e Widely used in man pages to represent a backslash > output glyph. It works reliably as long as the .ec > request is not used, which should never happen in > man pages, and it is slightly more portable than the > more exact ‘\(rs’ (“reverse solidus”) escape se‐ > quence. > > > > + return 1; > > + } > > + > > + fd = open(argv[1], O_RDWR | O_NONBLOCK | O_NOCTTY); > > + if (fd < 0) { > > + perror("open"); > > + return 1; > > exit(EXIT_FAILURE); > > > + } > > + > > + rc = ioctl(fd, TCGETS2, &tio2); > > + if (rc) { > > + perror("TCGETS2"); > > + close(fd); > > + return 1; > > exit(3) > > > + } > > + > > + printf("%u\\n", tio2.c_ospeed); > > \e > > > + > > + if (argc == 3) { > > + tio2.c_cflag &= ~CBAUD; > > + tio2.c_cflag |= BOTHER; > > + tio2.c_ospeed = tio2.c_ispeed = atoi(argv[2]); > > + > > + rc = ioctl(fd, TCSETS2, &tio2); > > + if (rc) { > > + perror("TCSETS2"); > > + close(fd); > > + return 1; > > exit(3) > > > + } > > + } > > + > > + close(fd); > > + return 0; > > exit(3) Interesting... Do you prefer to use exit(EXIT_SUCCESS) instead of return 0? > > +#endif > > +} > > +.EE > > .SH SEE ALSO > > .BR ldattach (1), > > .BR ioctl (2), > > > > > -- > Alejandro Colomar > Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/ > http://www.alejandro-colomar.es/