boot: introduce option to pass barebox-enabled watchdog to systemd

Like Linux, barebox supports co-existence of multiple watchdog
devices. On boot, barebox enables only the default watchdog, which
is defined as the watchdog with highest non-zero priority.

The kernel handles all watchdogs the same and defers to userspace,
which watchdogs to service. It can be useful to have barebox tell
the system, which watchdog it activated, so it can service the same.

Having this feature behind a global variable adds 354 bytes to a
LZO compressed THUMB2 barebox. Users can opt out by toggling the
Kconfig option, which defaults to off.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 13 insertions, 3 deletions

diff --git a/common/boot.c b/common/boot.c
index c6ec22873d..1657608d33 100644
--- a/common/boot.c
+++ b/common/boot.c
@@ -116,6 +116,13 @@ void boot_set_watchdog_timeout(unsigned int timeout)
 	boot_watchdog_timeout = timeout;
 }
 
+static struct watchdog *boot_enabled_watchdog;
+
+struct watchdog *boot_get_enabled_watchdog(void)
+{
+	return boot_enabled_watchdog;
+}
+
 static char *global_boot_default;
 static char *global_user;
 
@@ -143,10 +150,13 @@ int boot_entry(struct bootentry *be, int verbose, int dryrun)
 	printf("Booting entry '%s'\n", be->title);
 
 	if (IS_ENABLED(CONFIG_WATCHDOG) && boot_watchdog_timeout) {
-		ret = watchdog_set_timeout(watchdog_get_default(),
-					   boot_watchdog_timeout);
-		if (ret)
+		boot_enabled_watchdog = watchdog_get_default();
+
+		ret = watchdog_set_timeout(boot_enabled_watchdog, boot_watchdog_timeout);
+		if (ret) {
 			pr_warn("Failed to enable watchdog: %s\n", strerror(-ret));
+			boot_enabled_watchdog = NULL;
+		}
 	}
 
 	ret = be->boot(be, verbose, dryrun);