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>

diff --git a/inittab.c b/inittab.c
index 45118f4f1eaf05867e98040562131dc7df8e233e..2c2270cf68d367bcb882e0467d2bfd2456111daa 100644 (file)
--- a/inittab.c
+++ b/inittab.c
@@ -183,7 +183,15 @@ static void askconsole(struct init_action *a)
        char line[256], *tty, *split;
        int i;
 
+       /* First, try console= on the kernel command line,
+        * then fallback to /sys/class/tty/console/active,
+        * which should work when linux,stdout-path (or equivalent)
+        * is in the device tree
+        */
        tty = get_cmdline_val("console", line, sizeof(line));
+       if (tty == NULL) {
+               tty = get_active_console(line, sizeof(line));
+       }
        if (tty != NULL) {
                split = strchr(tty, ',');
                if (split != NULL)

diff --git a/utils/utils.c b/utils/utils.c
index 8d76129a02b334a25a89dcc4a40f7de2de733faf..e90feecb47f3e555ed67cf79ff907561039d00d7 100644 (file)
--- 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 989ceb270e3addb0c6f518327e806149cca15b6b..898bcc4f050b30d49676cd71e750f898ebff6630 100644 (file)
--- 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);