[PATCH v2] ioctl_tty.2: Add example how to get or set baudrate on the serial port

["Pali Rohár via Libc-alpha" <libc-alpha@sourceware.org>]

Signed-off-by: Pali Rohár <pali@kernel.org>

---
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 | 61 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/man2/ioctl_tty.2 b/man2/ioctl_tty.2
index 967b5c4c78c9..771a9a470bf0 100644
--- a/man2/ioctl_tty.2
+++ b/man2/ioctl_tty.2
@@ -748,6 +748,67 @@ main(void)
     close(fd);
 }
 .EE
+.PP
+Get or set arbitrary baudrate on the serial port.
+.PP
+.EX
+#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[])
+{
+#if !defined(TCGETS2) || !defined(TCSETS2) || !defined(BOTHER)
+    fprintf(stderr, "TCGETS2, TCSETS2 or BOTHER is unsupported\en");
+    /* Program may fallback to TCGETS/TCSETS with Bnnn constants */
+    exit(EXIT_FAILURE);
+#else
+    struct termios2 tio2;
+    int fd, rc;
+
+    if (argc != 2 && argc != 3) {
+        fprintf(stderr, "Usage: %s device [new_baudrate]\en", argv[0]);
+        exit(EXIT_FAILURE);
+    }
+
+    fd = open(argv[1], O_RDWR | O_NONBLOCK | O_NOCTTY);
+    if (fd < 0) {
+        perror("open");
+        exit(EXIT_FAILURE);
+    }
+
+    rc = ioctl(fd, TCGETS2, &tio2);
+    if (rc) {
+        perror("TCGETS2");
+        close(fd);
+        exit(EXIT_FAILURE);
+    }
+
+    printf("%u\en", tio2.c_ospeed);
+
+    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);
+            exit(EXIT_FAILURE);
+        }
+    }
+
+    close(fd);
+    exit(EXIT_SUCCESS);
+#endif
+}
+.EE
 .SH SEE ALSO
 .BR ldattach (1),
 .BR ioctl (2),
-- 
2.20.1