From: "Alejandro Colomar \(man-pages\) via Libc-alpha" <libc-alpha@sourceware.org>
To: "Pali Rohár" <pali@kernel.org>
Cc: "Marek Behún" <kabel@kernel.org>,
"G. Branden Robinson" <g.branden.robinson@gmail.com>,
libc-alpha@sourceware.org,
"Michael Kerrisk" <mtk.manpages@gmail.com>,
linux-man@vger.kernel.org
Subject: Re: [PATCH v4] ioctl_tty.2: Add example how to get or set baudrate on the serial port
Date: Fri, 10 Sep 2021 15:37:54 +0200 [thread overview]
Message-ID: <56938369-cd99-d768-55da-5eac4cd268d4@gmail.com> (raw)
In-Reply-To: <20210831203436.hy52aimer5hozb6r@pali>
Hi, Pali!
On 8/31/21 10:34 PM, Pali Rohár wrote:
> 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?
Sorry, I started to fix the licensing issues Greg pointed out, and
forgot about this.
I assume it's good since you have been doing a lot of related work in
recent patches. I'll only point out a cosmetic issue with the
preprocessor stuff: I'd indent with a single space after '#' to clarify
preprocessor #if #else #endif relationships and improve readability. I
also prefer '#if [!]defined()' rather than '#if[n]def' (except for
include guards); and there seems to be a mix in the existing pages, so
I'll standardize that way from now on.
For example:
#if !defined a
#else
# if defined b
# endif
#endif
However, I applied those changes myself in a following patch, so you
don't worry about them.
Patch applied!
Thanks,
Alex
>
>> ---
>> 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
>>
--
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/
next prev parent reply other threads:[~2021-09-10 13:38 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
2021-09-10 13:37 ` Alejandro Colomar (man-pages) via Libc-alpha [this message]
2021-09-10 13:39 ` Pali Rohár via Libc-alpha
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