scan: print errno message when system call fails

MultiCAN/src/drivers/scan/ellsi.c

@@ -226,7 +226,8 @@ static ssize_t ellsi_read(void *pvt, struct can_frame *frame) {
             ntohl(state->msg.header.subcommand),
             ntohl(state->msg.header.payloadLen));
         if (nbytes < 0) {
-            fprintf(stderr, "ellsi_read: recv failed\n");
+            errbuf_t buf;
+            fprintf(stderr, "ellsi_read: recv failed (%s)\n", ERRNO_STR(buf));
             return -1;
         }
         if (state->msg.header.magic != htonl(ELLSI_MAGIC)) {
@@ -245,7 +246,8 @@ static ssize_t ellsi_read(void *pvt, struct can_frame *frame) {
             assert(state->msg.header.payloadLen == 0);
             nbytes = write(state->sock, &state->msg.header, sizeof(state->msg.header));
             if (nbytes < sizeof(state->msg.header)) {
-                fprintf(stderr, "ellsi_read: reply to heartbeat failed\n");
+                errbuf_t buf;
+                fprintf(stderr, "ellsi_read: reply to heartbeat failed (%s)\n", ERRNO_STR(buf));
             }
             break;
 #if 0
@@ -335,7 +337,9 @@ static int ellsi_register(ellsi_state_t *state) {
         ELLSI_MAGIC, ELLSI_CMD_REGISTER, ELLSI_SUBCMD_AUTOACK);
     r = write(state->sock, &msg, sizeof(msg));
     if (r < 0) {
-        fprintf(stderr, "ellsi_register: write failed\n"); return r;
+        errbuf_t buf;
+        fprintf(stderr, "ellsi_register: write failed (%s)\n", ERRNO_STR(buf));
+        return r;
     }
     return ellsi_check(state->sock);
 }
@@ -365,14 +369,18 @@ static int ellsi_set_baudrate(ellsi_state_t *state, int baudrate) {
         ELLSI_MAGIC, ELLSI_CMD_CTRL, ELLSI_IOCTL_CAN_SET_BAUDRATE, code);
     r = write(state->sock, &msg, sizeof(msg));
     if (r < 0) {
-        fprintf(stderr, "ellsi_set_baudrate: write failed\n"); return r;
+        errbuf_t buf;
+        fprintf(stderr, "ellsi_set_baudrate: write failed (%s)\n", ERRNO_STR(buf));
+        return r;
     }
     msg.header.command = htonl(ELLSI_CMD_CTRL);
     msg.header.subcommand = htonl(ELLSI_IOCTL_GET_LAST_STATE);
     msg.header.payloadLen = htonl(sizeof(msg.payload));
     r = write(state->sock, &msg, sizeof(msg));
     if (r < 0) {
-        fprintf(stderr, "ellsi_set_baudrate: write failed\n"); return r;
+        errbuf_t buf;
+        fprintf(stderr, "ellsi_set_baudrate: write failed (%s)\n", ERRNO_STR(buf));
+        return r;
     }
     return ellsi_check(state->sock);
 }
@@ -395,14 +403,18 @@ static int ellsi_add_can_ids(ellsi_state_t *state) {
         ELLSI_MAGIC, ELLSI_CMD_CTRL, ELLSI_IOCTL_CAN_ID_ADD);
     r = write(state->sock, &msg, sizeof(msg));
     if (r < 0) {
-        fprintf(stderr, "ellsi_add_can_ids: write failed\n"); return r;
+        errbuf_t buf;
+        fprintf(stderr, "ellsi_add_can_ids: write failed (%s)\n", ERRNO_STR(buf));
+        return r;
     }
     msg.header.command = htonl(ELLSI_CMD_CTRL);
     msg.header.subcommand = htonl(ELLSI_IOCTL_GET_LAST_STATE);
     msg.header.payloadLen = htonl(sizeof(msg.payload));
     r = write(state->sock, &msg, sizeof(msg));
     if (r < 0) {
-        fprintf(stderr, "ellsi_add_can_ids: write failed\n"); return r;
+        errbuf_t buf;
+        fprintf(stderr, "ellsi_add_can_ids: write failed (%s)\n", ERRNO_STR(buf));
+        return r;
     }
     return ellsi_check(state->sock);
 }