tools/arch/x86/dell-uart-backlight-emulator/dell-uart-backlight-emulator.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Dell AIO Serial Backlight board emulator for testing
   4  * the Linux dell-uart-backlight driver.
   5  *
   6  * Copyright (C) 2024 Hans de Goede <hansg@kernel.org>
   7  */
   8 #include <errno.h>
   9 #include <fcntl.h>
  10 #include <signal.h>
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14 #include <sys/ioctl.h>
  15 #include <sys/stat.h>
  16 #include <sys/types.h>
  17 #include <sys/un.h>
  18 #include <termios.h>
  19 #include <unistd.h>
  20
  21 int serial_fd;
  22 int brightness = 50;
  23
  24 static unsigned char dell_uart_checksum(unsigned char *buf, int len)
  25 {
  26         unsigned char val = 0;
  27
  28         while (len-- > 0)
  29                 val += buf[len];
  30
  31         return val ^ 0xff;
  32 }
  33
  34 /* read() will return -1 on SIGINT / SIGTERM causing the mainloop to cleanly exit */
  35 void signalhdlr(int signum)
  36 {
  37 }
  38
  39 int main(int argc, char *argv[])
  40 {
  41         struct sigaction sigact = { .sa_handler = signalhdlr };
  42         unsigned char buf[4], csum, response[32];
  43         const char *version_str = "PHI23-V321";
  44         struct termios tty, saved_tty;
  45         int ret, idx, len = 0;
  46
  47         if (argc != 2) {
  48                 fprintf(stderr, "Invalid or missing arguments\n");
  49                 fprintf(stderr, "Usage: %s <serial-port>\n", argv[0]);
  50                 return 1;
  51         }
  52
  53         serial_fd = open(argv[1], O_RDWR | O_NOCTTY);
  54         if (serial_fd == -1) {
  55                 fprintf(stderr, "Error opening %s: %s\n", argv[1], strerror(errno));
  56                 return 1;
  57         }
  58
  59         ret = tcgetattr(serial_fd, &tty);
  60         if (ret == -1) {
  61                 fprintf(stderr, "Error getting tcattr: %s\n", strerror(errno));
  62                 goto out_close;
  63         }
  64         saved_tty = tty;
  65
  66         cfsetspeed(&tty, 9600);
  67         cfmakeraw(&tty);
  68         tty.c_cflag &= ~CSTOPB;
  69         tty.c_cflag &= ~CRTSCTS;
  70         tty.c_cflag |= CLOCAL | CREAD;
  71
  72         ret = tcsetattr(serial_fd, TCSANOW, &tty);
  73         if (ret == -1) {
  74                 fprintf(stderr, "Error setting tcattr: %s\n", strerror(errno));
  75                 goto out_restore;
  76         }
  77
  78         sigaction(SIGINT, &sigact, 0);
  79         sigaction(SIGTERM, &sigact, 0);
  80
  81         idx = 0;
  82         while (read(serial_fd, &buf[idx], 1) == 1) {
  83                 if (idx == 0) {
  84                         switch (buf[0]) {
  85                         /* 3 MSB bits: cmd-len + 01010 SOF marker */
  86                         case 0x6a: len = 3; break;
  87                         case 0x8a: len = 4; break;
  88                         default:
  89                                 fprintf(stderr, "Error unexpected first byte: 0x%02x\n", buf[0]);
  90                                 continue; /* Try to sync up with sender */
  91                         }
  92                 }
  93
  94                 /* Process msg when len bytes have been received */
  95                 if (idx != (len - 1)) {
  96                         idx++;
  97                         continue;
  98                 }
  99
 100                 /* Reset idx for next command */
 101                 idx = 0;
 102
 103                 csum = dell_uart_checksum(buf, len - 1);
 104                 if (buf[len - 1] != csum) {
 105                         fprintf(stderr, "Error checksum mismatch got 0x%02x expected 0x%02x\n",
 106                                 buf[len - 1], csum);
 107                         continue;
 108                 }
 109
 110                 switch ((buf[0] << 8) | buf[1]) {
 111                 case 0x6a06: /* cmd = 0x06, get version */
 112                         len = strlen(version_str);
 113                         strcpy((char *)&response[2], version_str);
 114                         printf("Get version, reply: %s\n", version_str);
 115                         break;
 116                 case 0x8a0b: /* cmd = 0x0b, set brightness */
 117                         if (buf[2] > 100) {
 118                                 fprintf(stderr, "Error invalid brightness param: %d\n", buf[2]);
 119                                 continue;
 120                         }
 121
 122                         len = 0;
 123                         brightness = buf[2];
 124                         printf("Set brightness %d\n", brightness);
 125                         break;
 126                 case 0x6a0c: /* cmd = 0x0c, get brightness */
 127                         len = 1;
 128                         response[2] = brightness;
 129                         printf("Get brightness, reply: %d\n", brightness);
 130                         break;
 131                 case 0x8a0e: /* cmd = 0x0e, set backlight power */
 132                         if (buf[2] != 0 && buf[2] != 1) {
 133                                 fprintf(stderr, "Error invalid set power param: %d\n", buf[2]);
 134                                 continue;
 135                         }
 136
 137                         len = 0;
 138                         printf("Set power %d\n", buf[2]);
 139                         break;
 140                 default:
 141                         fprintf(stderr, "Error unknown cmd 0x%04x\n",
 142                                 (buf[0] << 8) | buf[1]);
 143                         continue;
 144                 }
 145
 146                 /* Respond with <total-len> <cmd> <data...> <csum> */
 147                 response[0] = len + 3; /* response length in bytes */
 148                 response[1] = buf[1];  /* ack cmd */
 149                 csum = dell_uart_checksum(response, len + 2);
 150                 response[len + 2] = csum;
 151                 ret = write(serial_fd, response, response[0]);
 152                 if (ret != (response[0]))
 153                         fprintf(stderr, "Error writing %d bytes: %d\n",
 154                                 response[0], ret);
 155         }
 156
 157         ret = 0;
 158 out_restore:
 159         tcsetattr(serial_fd, TCSANOW, &saved_tty);
 160 out_close:
 161         close(serial_fd);
 162         return ret;
 163 }