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comparison sw/libserial/initflush.c @ 6:a10657f8024e

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sw: move initflush.c module into libserial
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 12 Oct 2024 19:42:19 +0000
parents sw/mcsi-rx/initflush.c@de85c3680d7e
children
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5:3ae4a6ca5639 6:a10657f8024e
1 /*
2 * FTDI chip+driver combo (specifically the combination of FTDI chips and
3 * ftdi_sio driver in Linux, not sure who is the actual culprit) exhibits
4 * this unpleasant behaviour: even though we request "please flush all
5 * previous input" when we set our termios params, old accumulated serial
6 * Rx bytes still remain in some buffer somewhere, and a newly started
7 * serial application receives this stale garbage. As a workaround,
8 * we do an additional flush of our own: we put the fd in non-blocking mode
9 * and keep reading and discarding data until we get EAGAIN or EWOULDBLOCK.
10 */
11
12 #include <sys/types.h>
13 #include <sys/errno.h>
14 #include <stdio.h>
15 #include <stdlib.h>
16 #include <unistd.h>
17
18 extern int target_fd;
19
20 void
21 init_serial_flush()
22 {
23 u_char buf[512];
24 int cc;
25
26 set_serial_nonblock(1);
27 for (;;) {
28 cc = read(target_fd, buf, sizeof buf);
29 if (cc <= 0)
30 break;
31 }
32 if (cc == 0) {
33 fprintf(stderr,
34 "read EOF from serial port during initial flush\n");
35 exit(1);
36 }
37 if (errno == EAGAIN || errno == EWOULDBLOCK)
38 return; /* success */
39 perror("serial port read");
40 exit(1);
41 }