inittab: detect active console from kernel if no console= specified

The default serial console can be set in the device tree
using the linux,stdout-path parameter (or equivalent from ACPI).

This is important for universal booting (EFI/EBBR) on ARM platforms
where the default console can be different (e.g ttyS0 vs ttyAMA0).

Signed-off-by: Mathew McBride <matt@traverse.com.au>

2 files changed, 23 insertions, 0 deletions

diff --git a/utils/utils.c b/utils/utils.c
index 8d76129..e90feec 100644
--- a/utils/utils.c
+++ b/utils/utils.c
@@ -135,6 +135,28 @@ blobmsg_list_equal(struct blobmsg_list *l1, struct blobmsg_list *l2)
 	return true;
 }
 
+char *get_active_console(char *out, int len)
+{
+	char line[CMDLINE_SIZE + 1];
+	int fd = open("/sys/class/tty/console/active", O_RDONLY);
+	ssize_t r = read(fd, line, sizeof(line) - 1);
+
+	close(fd);
+
+	if (r <= 0)
+		return NULL;
+
+	/* The active file is terminated by a newline which we need to strip */
+	char *newline = strtok(line, "\n");
+
+	if (newline != NULL) {
+		strncpy(out, newline, len);
+		return out;
+	}
+
+	return NULL;
+}
+
 char* get_cmdline_val(const char* name, char* out, int len)
 {
 	char line[CMDLINE_SIZE + 1], *c, *sptr;
diff --git a/utils/utils.h b/utils/utils.h
index 989ceb2..898bcc4 100644
--- a/utils/utils.h
+++ b/utils/utils.h
@@ -52,6 +52,7 @@ void blobmsg_list_free(struct blobmsg_list *list);
 bool blobmsg_list_equal(struct blobmsg_list *l1, struct blobmsg_list *l2);
 void blobmsg_list_move(struct blobmsg_list *list, struct blobmsg_list *src);
 char *get_cmdline_val(const char *name, char *out, int len);
+char *get_active_console(char *out, int len);
 
 int patch_fd(const char *device, int fd, int flags);
 int patch_stdio(const char *device);