configs: apple: Override scan_dev_for_boot_part from distro_bootcmds

Asahi explores the idea of using a distinct EFI system partition per
installation. This will only work if u-boot boots only a specific ESP.
The override for scan_dev_for_boot_part tests for a UUID match before it
tries to boot from a partition.

The optional UUID for the ESP can be specified by m1n1 by setting the
"boot_esp" environment variable in the "/config" "bootcmd" property.

/ {
	config {
		bootcmd = "setenv boot_esp $UUID; run distro_bootcmd; env delete boot_esp; run distro_bootcmd;";
	};
};

Signed-off-by: Janne Grunau <j@jannau.net>

include/configs/apple.h

@@ -27,8 +27,27 @@
 
 #include <config_distro_bootcmd.h>
 
+#define BOOTENV_OVERRIDE \
+	"scan_dev_for_boot_part="                                         \
+		"part list ${devtype} ${devnum} -bootable devplist; "     \
+		"env exists devplist || setenv devplist 1; "              \
+		"for distro_bootpart in ${devplist}; do "                 \
+			"part uuid ${devtype} ${devnum}:${distro_bootpart} " \
+					"bootuuid; "                      \
+			"if test U${bootuuid} = U${boot_esp} -o -z ${boot_esp}; then " \
+			"echo bootuuid=${bootuuid} boot_esp=${boot_esp}; "\
+			"if fstype ${devtype} "                           \
+					"${devnum}:${distro_bootpart} "   \
+					"bootfstype; then "               \
+				"run scan_dev_for_boot; "                 \
+			"fi; "                                            \
+			"fi; "                                            \
+		"done; "                                                  \
+		"setenv devplist\0"
+
 #define CONFIG_EXTRA_ENV_SETTINGS \
 	ENV_DEVICE_SETTINGS \
-	BOOTENV
+	BOOTENV \
+	BOOTENV_OVERRIDE
 
 #endif