1 /* SPDX-License-Identifier: BSD-2-Clause */
2 /*
3  * Copyright (C) 2017 The Android Open Source Project
4  */
5 
6 #ifndef __ANDROID_AB_H
7 #define __ANDROID_AB_H
8 
9 struct blk_desc;
10 struct disk_partition;
11 
12 /* Android standard boot slot names are 'a', 'b', 'c', ... */
13 #define BOOT_SLOT_NAME(slot_num) ('a' + (slot_num))
14 
15 /* Number of slots */
16 #define NUM_SLOTS 2
17 
18 /**
19  * Select the slot where to boot from.
20  *
21  * On Android devices with more than one boot slot (multiple copies of the
22  * kernel and system images) selects which slot should be used to boot from and
23  * registers the boot attempt. This is used in by the new A/B update model where
24  * one slot is updated in the background while running from the other slot. If
25  * the selected slot did not successfully boot in the past, a boot attempt is
26  * registered before returning from this function so it isn't selected
27  * indefinitely.
28  *
29  * @param[in] dev_desc Place to store the device description pointer
30  * @param[in] part_info Place to store the partition information
31  * @return The slot number (>= 0) on success, or a negative on error
32  */
33 int ab_select_slot(struct blk_desc *dev_desc, struct disk_partition *part_info);
34 
35 #endif /* __ANDROID_AB_H */
36