From: "Pali Rohár via Libc-alpha" <libc-alpha@sourceware.org>
To: linux-man@vger.kernel.org,
Alejandro Colomar <alx.manpages@gmail.com>,
Michael Kerrisk <mtk.manpages@gmail.com>
Cc: "Marek Behún" <kabel@kernel.org>,
"G. Branden Robinson" <g.branden.robinson@gmail.com>,
libc-alpha@sourceware.org
Subject: Re: [PATCH v4] ioctl_tty.2: Add example how to get or set baudrate on the serial port
Date: Tue, 31 Aug 2021 22:34:36 +0200 [thread overview]
Message-ID: <20210831203436.hy52aimer5hozb6r@pali> (raw)
In-Reply-To: <20210810194928.16408-1-pali@kernel.org>
On Tuesday 10 August 2021 21:49:28 Pali Rohár wrote:
> Setting custom baudrate for which is not defined Bnnn constant is possible
> via BOTHER flag and then filling speed in c_ospeed and c_ispeed fields.
>
> These two fields are either in struct termios or struct termios2. Former
> belongs to TCGETS/TCSETS ioctls, latter to TCGETS2/TCSETS2 ioctls.
>
> BOTHER flag with these two fields and new struct termios2 is not supported
> by older versions of include header files.
>
> Some architectures (e.g. amd64) provide both struct termios and struct
> termios2, but c_ospeed and c_ispeed are only in struct termios2.
>
> Some other architectures (e.g. alpha) provide both struct termios and struct
> termios2 and both have c_ospeed and c_ispeed fields.
>
> And some other architectures (e.g. powerpc) provide only struct termios
> (no struct termios2) and it has c_ospeed and c_ispeed fields.
>
> So basically to support all architectures it is needed to use
> struct termios2 when TCGETS2/TCSETS2 is supported. Otherwise it is needed
> to use struct termios with TCGETS/TCSETS (case for e.g. powerpc).
>
> Setting input baudrate is done via IBSHIFT macro.
>
> Signed-off-by: Pali Rohár <pali@kernel.org>
Hello! Do you have any comments on this patch?
> ---
> Changes in v4:
> * Add SPDX-License-Identifier
> * Correctly process split baudrates (separate output and input) via IBSHIFT
> * Update commit message
>
> Changes in v3:
> * Check support for custom baudrate only based on BOTHER macro
> * Use TCGETS/TCSETS/termios when TCGETS2/TCSETS2/termios2 is not available
>
> Changes in v2:
> * Use \e for backslash
> * Use exit(EXIT_*) instead of return num
> * Sort includes
> * Add comment about possible fallback
> ---
> man2/ioctl_tty.2 | 100 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 100 insertions(+)
>
> diff --git a/man2/ioctl_tty.2 b/man2/ioctl_tty.2
> index abfdc1e21fe9..7b2b03ff6757 100644
> --- a/man2/ioctl_tty.2
> +++ b/man2/ioctl_tty.2
> @@ -796,6 +796,106 @@ main(void)
> close(fd);
> }
> .EE
> +.PP
> +Get or set arbitrary baudrate on the serial port.
> +.PP
> +.EX
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +
> +#include <asm/termbits.h>
> +#include <fcntl.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/ioctl.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +
> +int
> +main(int argc, char *argv[])
> +{
> +#ifndef BOTHER
> + fprintf(stderr, "BOTHER is unsupported\en");
> + /* Program may fallback to TCGETS/TCSETS with Bnnn constants */
> + exit(EXIT_FAILURE);
> +#else
> + /* Declare tio structure, its type depends on supported ioctl */
> +#ifdef TCGETS2
> + struct termios2 tio;
> +#else
> + struct termios tio;
> +#endif
> + int fd, rc;
> +
> + if (argc != 2 && argc != 3 && argc != 4) {
> + fprintf(stderr, "Usage: %s device [output [input] ]\en", argv[0]);
> + exit(EXIT_FAILURE);
> + }
> +
> + fd = open(argv[1], O_RDWR | O_NONBLOCK | O_NOCTTY);
> + if (fd < 0) {
> + perror("open");
> + exit(EXIT_FAILURE);
> + }
> +
> + /* Get the current serial port settings via supported ioctl */
> +#ifdef TCGETS2
> + rc = ioctl(fd, TCGETS2, &tio);
> +#else
> + rc = ioctl(fd, TCGETS, &tio);
> +#endif
> + if (rc) {
> + perror("TCGETS");
> + close(fd);
> + exit(EXIT_FAILURE);
> + }
> +
> + /* Change baud rate when more arguments were provided */
> + if (argc == 3 || argc == 4) {
> + /* Clear the current output baud rate and fill a new value */
> + tio.c_cflag &= ~CBAUD;
> + tio.c_cflag |= BOTHER;
> + tio.c_ospeed = atoi(argv[2]);
> +
> + /* Clear the current input baud rate and fill a new value */
> + tio.c_cflag &= ~(CBAUD << IBSHIFT);
> + tio.c_cflag |= BOTHER << IBSHIFT;
> + /* When 4th argument is not provided reuse output baud rate */
> + tio.c_ispeed = (argc == 4) ? atoi(argv[3]) : atoi(argv[2]);
> +
> + /* Set new serial port settings via supported ioctl */
> +#ifdef TCSETS2
> + rc = ioctl(fd, TCSETS2, &tio);
> +#else
> + rc = ioctl(fd, TCSETS, &tio);
> +#endif
> + if (rc) {
> + perror("TCSETS");
> + close(fd);
> + exit(EXIT_FAILURE);
> + }
> +
> + /* And get new values which were really configured */
> +#ifdef TCGETS2
> + rc = ioctl(fd, TCGETS2, &tio);
> +#else
> + rc = ioctl(fd, TCGETS, &tio);
> +#endif
> + if (rc) {
> + perror("TCGETS");
> + close(fd);
> + exit(EXIT_FAILURE);
> + }
> + }
> +
> + close(fd);
> +
> + printf("output baud rate: %u\en", tio.c_ospeed);
> + printf("input baud rate: %u\en", tio.c_ispeed);
> +
> + exit(EXIT_SUCCESS);
> +#endif
> +}
> +.EE
> .SH SEE ALSO
> .BR ldattach (1),
> .BR ioctl (2),
> --
> 2.20.1
>
next prev parent reply other threads:[~2021-08-31 20:35 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-30 9:53 [PATCH] ioctl_tty.2: Add example how to get or set baudrate on the serial port Pali Rohár via Libc-alpha
2021-07-30 11:47 ` Alejandro Colomar (man-pages) via Libc-alpha
2021-07-30 12:05 ` Pali Rohár via Libc-alpha
2021-07-30 12:21 ` Alejandro Colomar (man-pages) via Libc-alpha
2021-07-30 13:02 ` [PATCH v2] " Pali Rohár via Libc-alpha
2021-08-01 13:51 ` [PATCH v3] " Pali Rohár via Libc-alpha
2021-08-04 22:08 ` Pali Rohár via Libc-alpha
2021-08-05 5:52 ` Greg Kroah-Hartman via Libc-alpha
2021-08-05 8:22 ` Pali Rohár via Libc-alpha
2021-08-05 8:30 ` Greg Kroah-Hartman via Libc-alpha
2021-08-05 8:44 ` Pali Rohár via Libc-alpha
2021-08-05 8:50 ` Greg Kroah-Hartman via Libc-alpha
2021-08-05 9:51 ` Pali Rohár via Libc-alpha
2021-08-05 15:28 ` Alejandro Colomar (man-pages) via Libc-alpha
2021-08-05 16:14 ` Greg Kroah-Hartman via Libc-alpha
2021-08-05 16:45 ` Licensing example programs in man-pages (was [PATCH v3] ioctl_tty.2: Add example how to get or set baudrate on the serial port) Alejandro Colomar (man-pages) via Libc-alpha
2021-08-05 17:54 ` Greg Kroah-Hartman via Libc-alpha
2021-08-06 7:22 ` Alejandro Colomar (man-pages) via Libc-alpha
2021-08-06 8:32 ` Pali Rohár via Libc-alpha
2021-08-08 8:35 ` [PATCH v3] ioctl_tty.2: Add example how to get or set baudrate on the serial port Alejandro Colomar (man-pages) via Libc-alpha
2021-08-08 21:05 ` Pali Rohár via Libc-alpha
2021-08-08 21:19 ` Alejandro Colomar (man-pages) via Libc-alpha
2021-08-10 19:49 ` [PATCH v4] " Pali Rohár via Libc-alpha
2021-08-10 20:11 ` Pali Rohár via Libc-alpha
2021-08-31 20:34 ` Pali Rohár via Libc-alpha [this message]
2021-09-10 13:37 ` Alejandro Colomar (man-pages) via Libc-alpha
2021-09-10 13:39 ` Pali Rohár via Libc-alpha
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