boot: Add a boot_control HAL

The purpose of the boot control HAL is to communicate with the
bootloader and set various flags letting the bootloader know which
partition to boot

Change-Id: I15178abaaf9ca208b1e5300c9207cedbb7950a88

include/hardware/boot_control.h

@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_INCLUDE_HARDWARE_BOOT_CONTROL_H
+#define ANDROID_INCLUDE_HARDWARE_BOOT_CONTROL_H
+
+#include <hardware/hardware.h>
+
+__BEGIN_DECLS
+
+#define BOOT_CONTROL_MODULE_API_VERSION_0_1  HARDWARE_MODULE_API_VERSION(0, 1)
+
+/**
+ * The id of this module
+ */
+#define BOOT_CONTROL_HARDWARE_MODULE_ID "bootctrl"
+
+/*
+ * The Boot Control HAL is designed to allow for managing sets of redundant
+ * partitions, called slots, that can be booted from independantly. Slots
+ * are sets of partitions whose names differ only by a given suffix.
+ * They are identified here by a 0 indexed number, and associated with their
+ * suffix, which can be appended to the base name for any particular partition
+ * to find the one associated with that slot. The bootloader must pass the suffix
+ * of the currently active slot either through a kernel command line property at
+ * androidboot.slot_suffix, or the device tree at /firmware/android/slot_suffix.
+ * The primary use of this set up is to allow for background updates while the
+ * device is running, and to provide a fallback in the event that the update fails.
+ */
+
+
+/**
+ * Every hardware module must have a data structure named HAL_MODULE_INFO_SYM
+ * and the fields of this data structure must begin with hw_module_t
+ * followed by module specific information.
+ */
+typedef struct boot_control_module {
+    struct hw_module_t common;
+
+    /*
+     * (*init)() perform any initialization tasks needed for the HAL.
+     * This is called only once.
+     */
+    void (*init)(struct boot_control_module *module);
+
+    /*
+     * (*getNumberSlots)() returns the number of available slots.
+     * For instance, a system with a single set of partitions would return
+     * 1, a system with A/B would return 2, A/B/C -> 3...
+     */
+    unsigned (*getNumberSlots)(struct boot_control_module *module);
+
+    /*
+     * (*getCurrentSlot)() returns the value letting the system know
+     * whether the current slot is A or B. The meaning of A and B is
+     * left up to the implementer. It is assumed that if the current slot
+     * is A, then the block devices underlying B can be accessed directly
+     * without any risk of corruption.
+     * The returned value is always guaranteed to be strictly less than the
+     * value returned by getNumberSlots. Slots start at 0 and
+     * finish at getNumberSlots() - 1
+     */
+    unsigned (*getCurrentSlot)(struct boot_control_module *module);
+
+    /*
+     * (*markBootSuccessful)() marks the current slot
+     * as having booted successfully
+     *
+     * Returns 0 on success, -errno on error.
+     */
+    int (*markBootSuccessful)(struct boot_control_module *module);
+
+    /*
+     * (*setActiveBootSlot)() marks the slot passed in parameter as
+     * the active boot slot (see getCurrentSlot for an explanation
+     * of the "slot" parameter). This overrides any previous call to
+     * setSlotAsUnbootable.
+     * Returns 0 on success, -errno on error.
+     */
+    int (*setActiveBootSlot)(struct boot_control_module *module, unsigned slot);
+
+    /*
+     * (*setSlotAsUnbootable)() marks the slot passed in parameter as
+     * an unbootable. This can be used while updating the contents of the slot's
+     * partitions, so that the system will not attempt to boot a known bad set up.
+     * Returns 0 on success, -errno on error.
+     */
+    int (*setSlotAsUnbootable)(struct boot_control_module *module, unsigned slot);
+
+    /*
+     * (*isSlotBootable)() returns if the slot passed in parameter has
+     * booted successfully in the past.
+     * Returns 1 if the slot has booted successfully, 0 if it has not,
+     * and -errno on error.
+     */
+    int (*isSlotBootable)(struct boot_control_module *module, unsigned slot);
+
+    /*
+     * (*getSuffix)() returns the string suffix used by partitions that
+     * correspond to the slot number passed in parameter. The returned string
+     * is expected to be statically allocated and not need to be freed.
+     * Returns NULL if slot does not match an existing slot.
+     */
+    const char* (*getSuffix)(struct boot_control_module *module, unsigned slot);
+
+    void* reserved[32];
+} boot_control_module_t;
+
+
+__END_DECLS
+
+#endif  // ANDROID_INCLUDE_HARDWARE_BOOT_CONTROL_H