common: Implement A/B metadata

This patch determines the A/B-specific bootloader message structure
that is the basis for implementation of recovery and A/B update
functions. A/B metadata is stored in this structure and used to decide
which slot should we use to boot the device. Also some basic functions
for A/B metadata manipulation are implemented (like slot selection).

The patch was extracted from commits [1], [2] with some coding style
fixes.

[1] https://android-review.googlesource.com/c/platform/external/u-boot/+/729878/2
[2] https://android-review.googlesource.com/c/platform/external/u-boot/+/729880/2

Signed-off-by: Ruslan Trofymenko <ruslan.trofymenko@linaro.org>
Signed-off-by: Igor Opaniuk <igor.opaniuk@gmail.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/include/android_ab.h b/include/android_ab.h
new file mode 100644
index 00000000000..810906d22b3
--- /dev/null
+++ b/include/android_ab.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ */
+
+#ifndef __ANDROID_AB_H
+#define __ANDROID_AB_H
+
+#include <common.h>
+
+/* Android standard boot slot names are 'a', 'b', 'c', ... */
+#define BOOT_SLOT_NAME(slot_num) ('a' + (slot_num))
+
+/* Number of slots */
+#define NUM_SLOTS 2
+
+/**
+ * Select the slot where to boot from.
+ *
+ * On Android devices with more than one boot slot (multiple copies of the
+ * kernel and system images) selects which slot should be used to boot from and
+ * registers the boot attempt. This is used in by the new A/B update model where
+ * one slot is updated in the background while running from the other slot. If
+ * the selected slot did not successfully boot in the past, a boot attempt is
+ * registered before returning from this function so it isn't selected
+ * indefinitely.
+ *
+ * @param[in] dev_desc Place to store the device description pointer
+ * @param[in] part_info Place to store the partition information
+ * @return The slot number (>= 0) on success, or a negative on error
+ */
+int ab_select_slot(struct blk_desc *dev_desc, disk_partition_t *part_info);
+
+#endif /* __ANDROID_AB_H */