cttyhack: move /sys/class/tty/console/active check to the front

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 18 insertions, 13 deletions

diff --git a/shell/cttyhack.c b/shell/cttyhack.c
index 640f5b1fb..6ff867413 100644
--- a/shell/cttyhack.c
+++ b/shell/cttyhack.c
@@ -117,7 +117,24 @@ int cttyhack_main(int argc UNUSED_PARAM, char **argv)
                 /* We don't have ctty (or don't have "/dev/tty" node...) */
                 do {
 #ifdef __linux__
-                        int s;
+                        /* Note that this method does not use _stdin_.
+                         * Thus, "cttyhack </dev/something" can't be used.
+                         * However, this method is more reliable than
+                         * TIOCGSERIAL check, which assumes that all
+                         * serial lines follow /dev/ttySn convention -
+                         * which is not always the case.
+                         * Therefore, we use this methos first:
+                         */
+                        int s = open_read_close("/sys/class/tty/console/active",
+                                console + 5, sizeof(console) - 5);
+                        if (s > 0) {
+                                /* found active console via sysfs (Linux 2.6.38+)
+                                 * sysfs string looks like "ttyS0\n" so zap the newline:
+                                 */
+                                console[4 + s] = '\0';
+                                break;
+                        }
+
                         if (ioctl(0, VT_GETSTATE, &u.vt) == 0) {
                                 /* this is linux virtual tty */
                                 sprintf(console + 8, "S%u" + 1, (int)u.vt.v_active);
@@ -131,18 +148,6 @@ int cttyhack_main(int argc UNUSED_PARAM, char **argv)
                                 break;
                         }
 #endif
-#ifdef __linux__
-                        /* Note that this method is not related to _stdin_ */
-                        s = open_read_close("/sys/class/tty/console/active",
-                                console + 5, sizeof(console) - 5);
-                        if (s > 0) {
-                                /* found active console via sysfs (Linux 2.6.38+)
-                                 * sysfs string looks like "ttyS0\n" so zap the newline:
-                                 */
-                                console[4 + s] = '\0';
-                                break;
-                        }
-#endif
                         /* nope, could not find it */
                         console[0] = '\0';
                 } while (0);