Extend autocons to more use cases

If SPCR comes up blank, see if there is one and exactly one serial with carrier detect

Failing that, give DMI a chance to indicate a preference, for now just SuperMicro, since they have the most
inconsistent carrier detect behavior
but almost always consider ttyS1 to be the answer.

confluent_osdeploy/utils/autocons.c

@@ -7,6 +7,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
+#include <dirent.h>
 
 #define COM1 0x3f8
 #define COM2 0x2f8
@@ -19,6 +20,131 @@
 #define SPEED57600 6
 #define SPEED115200 7
 
+typedef struct {
+    char devnode[32];
+    speed_t speed;
+    int valid;
+} serial_port_t;
+
+serial_port_t process_spcr() {
+    serial_port_t result = {0};
+    char buff[128];
+    int fd;
+    uint64_t address;
+    int currspeed;
+    
+    result.valid = 0;
+    
+    fd = open("/sys/firmware/acpi/tables/SPCR", O_RDONLY);
+    if (fd < 0) {
+        return result;
+    }
+    
+    if (read(fd, buff, 80) < 80) {
+        close(fd);
+        return result;
+    }
+    close(fd);
+    
+    if (buff[8] != 2) return result; // revision 2
+    if (buff[36] != 0) return result; // 16550 only
+    if (buff[40] != 1) return result; // IO only
+    
+    address = *(uint64_t *)(buff + 44);
+    currspeed = buff[58];
+    
+    if (address == COM1) {
+        strncpy(result.devnode, "/dev/ttyS0", sizeof(result.devnode));
+    } else if (address == COM2) {
+        strncpy(result.devnode, "/dev/ttyS1", sizeof(result.devnode));
+    } else if (address == COM3) {
+        strncpy(result.devnode, "/dev/ttyS2", sizeof(result.devnode));
+    } else if (address == COM4) {
+        strncpy(result.devnode, "/dev/ttyS3", sizeof(result.devnode));
+    } else {
+        return result;
+    }
+    
+    if (currspeed == SPEED9600) {
+        result.speed = B9600;
+    } else if (currspeed == SPEED19200) {
+        result.speed = B19200;
+    } else if (currspeed == SPEED57600) {
+        result.speed = B57600;
+    } else if (currspeed == SPEED115200) {
+        result.speed = B115200;
+    } else {
+        return result;
+    }
+    
+    result.valid = 1;
+    return result;
+}
+
+serial_port_t identify_by_sys_vendor() {
+    serial_port_t result = {0};
+    char buff[128];
+    FILE *f;
+    
+    f = fopen("/sys/devices/virtual/dmi/id/sys_vendor", "r");
+    if (f) {
+        if (fgets(buff, sizeof(buff), f)) {
+            if (strstr(buff, "Supermicro")) {
+                strncpy(result.devnode, "/dev/ttyS1", sizeof(result.devnode));
+                result.speed = B115200;
+                result.valid = 1;
+            }
+        }
+        fclose(f);
+    }
+    return result;
+}
+
+serial_port_t search_serial_ports() {
+    serial_port_t result = {0};
+    DIR *dir;
+    struct dirent *entry;
+    int fd;
+    int status;
+    int numfound= 0;
+
+    dir = opendir("/dev");
+    if (!dir) {
+        return result;
+    }
+    
+    while ((entry = readdir(dir)) != NULL) {
+        if (strncmp(entry->d_name, "ttyS", 4) != 0) {
+            continue;
+        }
+        
+        char devpath[64];
+        snprintf(devpath, sizeof(devpath), "/dev/%s", entry->d_name);
+        
+        fd = open(devpath, O_RDWR | O_NOCTTY | O_NONBLOCK);
+        if (fd < 0) {
+            continue;
+        }
+        
+        if (ioctl(fd, TIOCMGET, &status) == 0) {
+            if (status & TIOCM_CAR) {
+                strncpy(result.devnode, devpath, sizeof(result.devnode));
+                numfound++;
+                result.speed = B115200;
+                
+            }
+        }
+        
+        close(fd);
+    }
+    
+    closedir(dir);
+    if (numfound == 1) {
+        result.valid = 1;
+    }
+    return result;
+}
+
 int main(int argc, char* argv[]) {
     struct termios tty;
     struct termios tty2;
@@ -36,46 +162,38 @@ int main(int argc, char* argv[]) {
     char* offset;
     uint64_t address;
     bufflen = 0;
-    tmpi = open("/sys/firmware/acpi/tables/SPCR", O_RDONLY);
-    if (tmpi < 0) {
-        exit(0);
-    }
-    if (read(tmpi, buff, 80) < 80) {
-        exit(0);
-    }
-    close(tmpi);
-    if (buff[8] != 2) exit(0); //revision 2
-    if (buff[36] != 0) exit(0); //16550 only
-    if (buff[40] != 1) exit(0); //IO only
-    address = *(uint64_t *)(buff + 44);
-    currspeed = buff[58];
-    offset = buff + 10;
-    if (address == COM1) {
-        strncpy(buff, "/dev/ttyS0", 128);
-    } else if (address == COM2) {
-        strncpy(buff, "/dev/ttyS1", 128);
-    } else if (address == COM3) {
-        strncpy(buff, "/dev/ttyS2", 128);
-    } else if (address == COM4) {
-        strncpy(buff, "/dev/ttyS3", 128);
-    } else {
+    #ifndef __x86_64__
+        // Only x86 needs autoconsole, other platforms have reasonable default serial console
+        exit(0);
+    #endif
+    serial_port_t spcr = process_spcr();
+    if (!spcr.valid) {
+        spcr = search_serial_ports();
+    }
+    if (!spcr.valid) {
+        spcr = identify_by_sys_vendor();
+    }
+    if (!spcr.valid) {
         exit(0);
     }
+    strncpy(buff, spcr.devnode, sizeof(buff));
+    offset = strchr(buff, 0);
+    currspeed = spcr.speed;
     ttyf = open(buff, O_RDWR | O_NOCTTY);
     if (ttyf < 0) {
         fprintf(stderr, "Unable to open tty\n");
         exit(1);
     }
-    if (currspeed == SPEED9600) {
+    if (currspeed == B9600) {
         cspeed = B9600;
         strncpy(offset, ",9600", 6);
-    } else if (currspeed == SPEED19200) {
+    } else if (currspeed == B19200) {
         cspeed = B19200;
         strncpy(offset, ",19200", 7);
-    } else if (currspeed == SPEED57600) {
+    } else if (currspeed == B57600) {
         cspeed = B57600;
         strncpy(offset, ",57600", 7);
-    } else if (currspeed == SPEED115200) {
+    } else if (currspeed == B115200) {
         cspeed = B115200;
         strncpy(offset, ",115200", 8);
     } else {