Merge branch '2022-04-25-initial-implementation-of-stdboot'

To quote the author:
The bootflow feature provide a built-in way for U-Boot to automatically
boot an Operating System without custom scripting and other customisation.
This is called 'standard boot' since it provides a standard way for
U-Boot to boot a distro, without scripting.

It introduces the following concepts:

   - bootdev - a device which can hold a distro
   - bootmeth - a method to scan a bootdev to find bootflows (owned by
                U-Boot)
   - bootflow - a description of how to boot (owned by the distro)

This series provides an implementation of these, enabled to scan for
bootflows from MMC, USB and Ethernet. It supports the existing distro
boot as well as the EFI loader flow (bootefi/bootmgr). It works
similiarly to the existing script-based approach, but is native to
U-Boot.

With this we can boot on a Raspberry Pi 3 with just one command:

   bootflow scan -lb

which means to scan, listing (-l) each bootflow and trying to boot each
one (-b). The final patch shows this.

With a standard way to identify boot devices, booting become easier. It
also should be possible to support U-Boot scripts, for backwards
compatibility only.

...

The design is described in these two documents:

https://drive.google.com/file/d/1ggW0KJpUOR__vBkj3l61L2dav4ZkNC12/view?usp=sharing

https://drive.google.com/file/d/1kTrflO9vvGlKp-ZH_jlgb9TY3WYG6FF9/view?usp=sharing

1 files changed, 80 insertions, 0 deletions

diff --git a/include/bootstd.h b/include/bootstd.h
new file mode 100644
index 00000000000..b002365f4f0
--- /dev/null
+++ b/include/bootstd.h
@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Standard U-Boot boot framework
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <[email protected]>
+ */
+
+#ifndef __bootstd_h
+#define __bootstd_h
+
+struct udevice;
+
+/**
+ * struct bootstd_priv - priv data for the bootstd driver
+ *
+ * This is attached to the (only) bootstd device, so there is only one instance
+ * of this struct. It provides overall information about bootdevs and bootflows.
+ *
+ * @prefixes: NULL-terminated list of prefixes to use for bootflow filenames,
+ *	e.g. "/", "/boot/"; NULL if none
+ * @bootdev_order: Order to use for bootdevs (or NULL if none), with each item
+ *	being a bootdev label, e.g. "mmc2", "mmc1";
+ * @cur_bootdev: Currently selected bootdev (for commands)
+ * @cur_bootflow: Currently selected bootflow (for commands)
+ * @glob_head: Head for the global list of all bootflows across all bootdevs
+ * @bootmeth_count: Number of bootmeth devices in @bootmeth_order
+ * @bootmeth_order: List of bootmeth devices to use, in order, NULL-terminated
+ */
+struct bootstd_priv {
+	const char **prefixes;
+	const char **bootdev_order;
+	struct udevice *cur_bootdev;
+	struct bootflow *cur_bootflow;
+	struct list_head glob_head;
+	int bootmeth_count;
+	struct udevice **bootmeth_order;
+};
+
+/**
+ * bootstd_get_bootdev_order() - Get the boot-order list
+ *
+ * This reads the boot order, e.g. {"mmc0", "mmc2", NULL}
+ *
+ * The list is alloced by the bootstd driver so should not be freed. That is the
+ * reason for all the const stuff in the function signature
+ *
+ * Return: list of string points, terminated by NULL; or NULL if no boot order
+ */
+const char *const *const bootstd_get_bootdev_order(struct udevice *dev);
+
+/**
+ * bootstd_get_prefixes() - Get the filename-prefixes list
+ *
+ * This reads the prefixes, e.g. {"/", "/bpot", NULL}
+ *
+ * The list is alloced by the bootstd driver so should not be freed. That is the
+ * reason for all the const stuff in the function signature
+ *
+ * Return: list of string points, terminated by NULL; or NULL if no boot order
+ */
+const char *const *const bootstd_get_prefixes(struct udevice *dev);
+
+/**
+ * bootstd_get_priv() - Get the (single) state for the bootstd system
+ *
+ * The state holds a global list of all bootflows that have been found.
+ *
+ * Return: 0 if OK, -ve if the uclass does not exist
+ */
+int bootstd_get_priv(struct bootstd_priv **stdp);
+
+/**
+ * bootstd_clear_glob() - Clear the global list of bootflows
+ *
+ * This removes all bootflows globally and across all bootdevs.
+ */
+void bootstd_clear_glob(void);
+
+#endif