Import of the watch repository from Pebble

src/fw/services/normal/accessory/smartstrap_attribute.h

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+/*
+ * Copyright 2024 Google LLC
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include "applib/app_smartstrap.h"
+#include "kernel/events.h"
+#include "services/normal/accessory/smartstrap_profiles.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+
+/*
+ * This module creates kernel-space structs to represent SmartstrapAttributes for the app. Because
+ * it is dealing with app buffers, the kernel-space structs are kept within smartstrap_attribute.c
+ * and they are referenced via the APIs using the user-space SmartstrapAttribute pointer. This
+ * SmartstrapAttribute pointer is actually just the user-space buffer pointer, but this fact is
+ * hidden from apps (and not particularly useful for them to know).
+ */
+
+/*
+ * FSM state transitions:
+ * +-------------------+-------------------+----------+---------------------------+
+ * | From State        | To State          | Task     | Event                     |
+ * +-------------------+-------------------+----------+---------------------------+
+ * | Idle              | RequestPending    | App      | *_read()                  |
+ * | Idle              | WritePending      | App      | *_begin_write()           |
+ * | WritePending      | RequestPending    | App      | *_end_write()             |
+ * | WritePending      | Idle              | App      | *_end_write() failed      |
+ * | RequestPending    | Idle              | KernelBG | Failed to send request    |
+ * | RequestPending    | RequestInProgress | KernelBG | Request sent successfully |
+ * | RequestInProgress | Idle              | KernelBG | Got response to request   |
+ * +-------------------+-------------------+----------+---------------------------+
+ * Notes:
+ * - Only the App task can move out of the Idle and WritePending states
+ * - Only KernelBG can move out of the RequestPending and RequestInProgress state
+ * - The lower-level smartstrap sending APIs are called only from KernelBG so we don't block the App
+ */
+typedef enum {
+  SmartstrapAttributeStateIdle = 0,
+  SmartstrapAttributeStateWritePending,
+  SmartstrapAttributeStateRequestPending,
+  SmartstrapAttributeStateRequestInProgress,
+  NumSmartstrapAttributeStates
+} SmartstrapAttributeState;
+
+typedef enum {
+  SmartstrapRequestTypeRead,
+  SmartstrapRequestTypeBeginWrite,
+  SmartstrapRequestTypeWrite,
+  SmartstrapRequestTypeWriteRead
+} SmartstrapRequestType;
+
+
+//! Initializes the smartstrap attribute code
+void smartstrap_attribute_init(void);
+
+//! Sends the next pending attribute request
+bool smartstrap_attribute_send_pending(void);
+
+//! Called by one of the profiles to send an event for an attribute.
+void smartstrap_attribute_send_event(SmartstrapEventType type, SmartstrapProfile profile,
+                                     SmartstrapResult result, uint16_t service_id,
+                                     uint16_t attribute_id, uint16_t read_length);
+
+//! Unregisters all attributes which the app has registered
+void smartstrap_attribute_unregister_all(void);
+
+// syscalls
+
+//! Registers a new attribute by creating a kernel-space struct to represent it
+bool sys_smartstrap_attribute_register(uint16_t service_id, uint16_t attribute_id, uint8_t *buffer,
+                                       size_t buffer_length);
+
+//! Unregisters an attribute
+void sys_smartstrap_attribute_unregister(SmartstrapAttribute *app_attr);
+
+//! Gets information on the specified attribute which has previously been created
+void sys_smartstrap_attribute_get_info(SmartstrapAttribute *app_attr, uint16_t *service_id,
+                                       uint16_t *attribute_id, size_t *length);
+
+//! Queues up a request for the specified attribute
+SmartstrapResult sys_smartstrap_attribute_do_request(SmartstrapAttribute *app_attr,
+                                                     SmartstrapRequestType type,
+                                                     uint16_t timeout_ms, uint32_t write_length);
+
+//! Called by app_smartstrap.c after the app's event callback is called for an attribute
+void sys_smartstrap_attribute_event_processed(SmartstrapAttribute *app_attr);