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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Dell AIO Serial Backlight board emulator for testing
* the Linux dell-uart-backlight driver.
*
* Copyright (C) 2024 Hans de Goede <hansg@kernel.org>
*/
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <termios.h>
#include <unistd.h>
int serial_fd;
int brightness = 50;
static unsigned char dell_uart_checksum(unsigned char *buf, int len)
{
unsigned char val = 0;
while (len-- > 0)
val += buf[len];
return val ^ 0xff;
}
/* read() will return -1 on SIGINT / SIGTERM causing the mainloop to cleanly exit */
void signalhdlr(int signum)
{
}
int main(int argc, char *argv[])
{
struct sigaction sigact = { .sa_handler = signalhdlr };
unsigned char buf[4], csum, response[32];
const char *version_str = "PHI23-V321";
struct termios tty, saved_tty;
int ret, idx, len = 0;
if (argc != 2) {
fprintf(stderr, "Invalid or missing arguments\n");
fprintf(stderr, "Usage: %s <serial-port>\n", argv[0]);
return 1;
}
serial_fd = open(argv[1], O_RDWR | O_NOCTTY);
if (serial_fd == -1) {
fprintf(stderr, "Error opening %s: %s\n", argv[1], strerror(errno));
return 1;
}
ret = tcgetattr(serial_fd, &tty);
if (ret == -1) {
fprintf(stderr, "Error getting tcattr: %s\n", strerror(errno));
goto out_close;
}
saved_tty = tty;
cfsetspeed(&tty, 9600);
cfmakeraw(&tty);
tty.c_cflag &= ~CSTOPB;
tty.c_cflag &= ~CRTSCTS;
tty.c_cflag |= CLOCAL | CREAD;
ret = tcsetattr(serial_fd, TCSANOW, &tty);
if (ret == -1) {
fprintf(stderr, "Error setting tcattr: %s\n", strerror(errno));
goto out_restore;
}
sigaction(SIGINT, &sigact, 0);
sigaction(SIGTERM, &sigact, 0);
idx = 0;
while (read(serial_fd, &buf[idx], 1) == 1) {
if (idx == 0) {
switch (buf[0]) {
/* 3 MSB bits: cmd-len + 01010 SOF marker */
case 0x6a: len = 3; break;
case 0x8a: len = 4; break;
default:
fprintf(stderr, "Error unexpected first byte: 0x%02x\n", buf[0]);
continue; /* Try to sync up with sender */
}
}
/* Process msg when len bytes have been received */
if (idx != (len - 1)) {
idx++;
continue;
}
/* Reset idx for next command */
idx = 0;
csum = dell_uart_checksum(buf, len - 1);
if (buf[len - 1] != csum) {
fprintf(stderr, "Error checksum mismatch got 0x%02x expected 0x%02x\n",
buf[len - 1], csum);
continue;
}
switch ((buf[0] << 8) | buf[1]) {
case 0x6a06: /* cmd = 0x06, get version */
len = strlen(version_str);
strcpy((char *)&response[2], version_str);
printf("Get version, reply: %s\n", version_str);
break;
case 0x8a0b: /* cmd = 0x0b, set brightness */
if (buf[2] > 100) {
fprintf(stderr, "Error invalid brightness param: %d\n", buf[2]);
continue;
}
len = 0;
brightness = buf[2];
printf("Set brightness %d\n", brightness);
break;
case 0x6a0c: /* cmd = 0x0c, get brightness */
len = 1;
response[2] = brightness;
printf("Get brightness, reply: %d\n", brightness);
break;
case 0x8a0e: /* cmd = 0x0e, set backlight power */
if (buf[2] != 0 && buf[2] != 1) {
fprintf(stderr, "Error invalid set power param: %d\n", buf[2]);
continue;
}
len = 0;
printf("Set power %d\n", buf[2]);
break;
default:
fprintf(stderr, "Error unknown cmd 0x%04x\n",
(buf[0] << 8) | buf[1]);
continue;
}
/* Respond with <total-len> <cmd> <data...> <csum> */
response[0] = len + 3; /* response length in bytes */
response[1] = buf[1]; /* ack cmd */
csum = dell_uart_checksum(response, len + 2);
response[len + 2] = csum;
ret = write(serial_fd, response, response[0]);
if (ret != (response[0]))
fprintf(stderr, "Error writing %d bytes: %d\n",
response[0], ret);
}
ret = 0;
out_restore:
tcsetattr(serial_fd, TCSANOW, &saved_tty);
out_close:
close(serial_fd);
return ret;
}
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