1 files changed, 81 insertions, 0 deletions
diff --git a/tdm/backend/getfd.c b/tdm/backend/getfd.c
new file mode 100644
index 000000000..307b2501c
--- /dev/null
+++ b/tdm/backend/getfd.c
@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/ioctl.h>
+#ifdef __linux__
+#include <linux/kd.h>
+#endif
+#include "getfd.h"
+
+/*
+ * getfd.c
+ *
+ * Get an fd for use with kbd/console ioctls.
+ * We try several things because opening /dev/console will fail
+ * if someone else used X (which does a chown on /dev/console).
+ */
+
+static int
+is_a_console(int fd) {
+	char arg;
+
+	arg = 0;
+#ifdef __OpenBSD__
+	return arg;
+#else
+	return (ioctl(fd, KDGKBTYPE, &arg) == 0
+		&& ((arg == KB_101) || (arg == KB_84)));
+#endif
+}
+
+static int
+open_a_console(const char *fnam) {
+	int fd;
+
+	/*
+	 * For ioctl purposes we only need some fd and permissions
+	 * do not matter. But setfont:activatemap() does a write.
+	 */
+	fd = open(fnam, O_RDWR);
+	if (fd < 0 && errno == EACCES)
+		fd = open(fnam, O_WRONLY);
+	if (fd < 0 && errno == EACCES)
+		fd = open(fnam, O_RDONLY);
+	if (fd < 0)
+		return -1;
+	if (!is_a_console(fd)) {
+		close(fd);
+		return -1;
+	}
+	return fd;
+}
+
+int getfd() {
+	int fd;
+
+	fd = open_a_console("/dev/tty");
+	if (fd >= 0)
+		return fd;
+
+	fd = open_a_console("/dev/tty0");
+	if (fd >= 0)
+		return fd;
+
+	fd = open_a_console("/dev/vc/0");
+	if (fd >= 0)
+		return fd;
+
+	fd = open_a_console("/dev/console");
+	if (fd >= 0)
+		return fd;
+
+	for (fd = 0; fd < 3; fd++)
+		if (is_a_console(fd))
+			return fd;
+
+	// "Couldnt get a file descriptor referring to the console
+	return -1;
+}
+