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