bootstd: Allow bootmeths to be marked as global

The current way of handling things like EFI bootmgr is a bit odd, since
that bootmeth handles selection of the bootdev itself. VBE needs to work
the same way, so we should support it properly.

Add a flag that indicates that the bootmeth is global, rather than being
invoked on each bootdev. Provide a helper to read a bootflow from the
bootmeth.

Signed-off-by: Simon Glass <sjg@chromium.org>

boot/Kconfig

@@ -349,6 +349,13 @@ config BOOTSTD_BOOTCOMMAND
 	  standard boot does not support all of the features of distro boot
 	  yet.
 
+config BOOTMETH_GLOBAL
+	bool
+	help
+	  Add support for global bootmeths. This feature is used by VBE and
+	  EFI bootmgr, since they take full control over which bootdevs are
+	  selected to boot.
+
 config BOOTMETH_DISTRO
 	bool "Bootdev support for distro boot"
 	select PXE_UTILS

boot/bootmeth-uclass.c

@@ -71,6 +71,20 @@ int bootmeth_read_file(struct udevice *dev, struct bootflow *bflow,
 	return ops->read_file(dev, bflow, file_path, addr, sizep);
 }
 
+int bootmeth_get_bootflow(struct udevice *dev, struct bootflow *bflow)
+{
+	const struct bootmeth_ops *ops = bootmeth_get_ops(dev);
+
+	if (!ops->read_bootflow)
+		return -ENOSYS;
+	memset(bflow, '\0', sizeof(*bflow));
+	bflow->dev = NULL;
+	bflow->method = dev;
+	bflow->state = BOOTFLOWST_BASE;
+
+	return ops->read_bootflow(dev, bflow);
+}
+
 /**
  * bootmeth_setup_iter_order() - Set up the ordering of bootmeths to scan
  *

boot/bootmeth_efi_mgr.c

@@ -61,6 +61,7 @@ static int bootmeth_efi_mgr_bind(struct udevice *dev)
 	struct bootmeth_uc_plat *plat = dev_get_uclass_plat(dev);
 
 	plat->desc = "EFI bootmgr flow";
+	plat->flags = BOOTMETHF_GLOBAL;
 
 	return 0;
 }
@@ -77,7 +78,7 @@ static const struct udevice_id efi_mgr_bootmeth_ids[] = {
 	{ }
 };
 
-U_BOOT_DRIVER(bootmeth_zefi_mgr) = {
+U_BOOT_DRIVER(bootmeth_efi_mgr) = {
 	.name		= "bootmeth_efi_mgr",
 	.id		= UCLASS_BOOTMETH,
 	.of_match	= efi_mgr_bootmeth_ids,