[PATCH 03/10] common: add optional systemd.hostname generation

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

To maintain unique hostnames, having barebox fix up its own hostname
appended by "-${global.serial_number} is a sane default. Add a Kconfig
option to enable this.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 common/Kconfig | 10 ++++++++++
 common/bootm.c |  9 ++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/common/Kconfig b/common/Kconfig
index 1e04d0403ad0..2d2be0f7c4f6 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -1254,6 +1254,16 @@ config MACHINE_ID
 	  Note: if no hashable information is available no machine id will be passed
 	  to the kernel.
 
+config SERIAL_NUMBER_FIXUP_SYSTEMD_HOSTNAME
+	bool "append board serial number to systemd.hostname= fixup"
+	depends on FLEXIBLE_BOOTARGS
+	help
+	  When a systemd.hostname= kernel command line argument is
+	  fixed up, append a `-${global.serial_number}' suffix.
+
+	  This option without effect if global.bootm.provide_hostname
+	  is unset.
+
 config SYSTEMD_OF_WATCHDOG
 	bool "inform devicetree-enabled kernel of used watchdog"
 	depends on WATCHDOG && OFTREE && FLEXIBLE_BOOTARGS
diff --git a/common/bootm.c b/common/bootm.c
index 5370e1485bc6..a26ea82684a6 100644
--- a/common/bootm.c
+++ b/common/bootm.c
@@ -864,6 +864,7 @@ int bootm_boot(struct bootm_data *bootm_data)
 
 	if (bootm_data->provide_hostname) {
 		const char *hostname = getenv_nonempty("global.hostname");
+		const char *suffix = NULL;
 		char *hostname_bootarg;
 
 		if (!hostname) {
@@ -878,7 +879,13 @@ int bootm_boot(struct bootm_data *bootm_data)
 			goto err_out;
 		}
 
-		hostname_bootarg = basprintf("systemd.hostname=%s", hostname);
+		if (IS_ENABLED(CONFIG_SERIAL_NUMBER_FIXUP_SYSTEMD_HOSTNAME))
+			suffix = barebox_get_serial_number();
+
+		hostname_bootarg = basprintf("systemd.hostname=%s%s%s",
+					     hostname, suffix ? "-" : "",
+					     suffix ?: "");
+
 		globalvar_add_simple("linux.bootargs.hostname", hostname_bootarg);
 		free(hostname_bootarg);
 	}
-- 
2.39.5