From patchwork Thu Nov 5 21:38:24 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Olivier TARTROU X-Patchwork-Id: 9568 Received: (qmail 109468 invoked by alias); 5 Nov 2015 21:38:29 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 109459 invoked by uid 89); 5 Nov 2015 21:38:29 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=0.6 required=5.0 tests=AWL, BAYES_00, FREEMAIL_FROM, SPF_PASS autolearn=ham version=3.3.2 X-HELO: mail-wm0-f48.google.com MIME-Version: 1.0 X-Received: by 10.28.11.207 with SMTP id 198mr6073090wml.47.1446759504945; Thu, 05 Nov 2015 13:38:24 -0800 (PST) Date: Thu, 5 Nov 2015 22:38:24 +0100 Message-ID: Subject: [patch] termios.3: Add missing details on behaviour of PARMRK From: Olivier TARTROU To: mtk.manpages@gmail.com Cc: linux-man@vger.kernel.org, libc-alpha@sourceware.org For a serial terminal, with a specific configuration, input bytes with value 0377 are passed to the program as two bytes, 0377 0377. This (correct) behaviour is described in the documentation of the GNU C Library (https://www.gnu.org/software/libc/manual/html_node/Input-Modes.html#Input-Modes) but not in the termios.3 man page. Problematic configuration: INPCK set, IGNPAR not set, PARMRK set, ISTRIP not set. This man page problem affects several users. Examples: * http://sourceforge.net/p/ftdi-usb-sio/mailman/message/4079724/ * http://mailman.uclinux.org/pipermail/uclinux-dev/2006-November/040984.html * ... The patch below corrects this problem. This patch applies to release 4.02. .SH NAME @@ -133,8 +135,17 @@ Ignore framing errors and parity errors. .TP .B PARMRK -If \fBIGNPAR\fP is not set, prefix a character with a parity error or -framing error with \\377 \\0. +If this bit is set, input bytes with parity or framing errors are +marked when passed to the program. This bit is meaningful only when +\fBINPCK\fP is set and \fBIGNPAR\fP is not set. +The way erroneous bytes are marked is with two preceding bytes, +\\377 and \\0. Thus, the program actually reads three bytes for one +erroneous byte received from the terminal. +If a valid byte has the value \\377, and \fBISTRIP\fP (see below) is +not set, the program might confuse it with the prefix that marks a +parity error. So a valid byte \\377 is passed to the program as two +bytes, \\377 \\377, in this case. + If neither \fBIGNPAR\fP nor \fBPARMRK\fP is set, read a character with a parity error or framing error as \\0. Best regards, Olivier TARTROU --- old/termios.3 2015-11-04 20:32:56.117200840 +0100 +++ new/termios.3 2015-11-04 23:31:23.165191198 +0100 @@ -36,6 +36,8 @@ .\" Added a section on canonical and noncanonical mode. .\" Enhanced the discussion of "raw" mode for cfmakeraw(). .\" Document CMSPAR. +.\" 2015-11-04, Olivier TARTROU : +.\" Reworked description of PARMRK from https://www.gnu.org/software/libc/manual/html_node/Input-Modes.html#Input-Modes .\" .TH TERMIOS 3 2015-03-02 "Linux" "Linux Programmer's Manual"