1 /**
2  * Copyright © 2020 IBM Corporation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *     http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 #pragma once
17 
18 #include <sdbusplus/bus.hpp>
19 #include <sdbusplus/exception.hpp>
20 
21 #include <map>
22 #include <string>
23 
24 namespace phosphor::power::regulators
25 {
26 
27 /**
28  * @class PresenceService
29  *
30  * Abstract base class that provides an interface to hardware presence data.
31  *
32  * The interface is used to determine whether hardware is present.
33  */
34 class PresenceService
35 {
36   public:
37     // Specify which compiler-generated methods we want
38     PresenceService() = default;
39     PresenceService(const PresenceService&) = delete;
40     PresenceService(PresenceService&&) = delete;
41     PresenceService& operator=(const PresenceService&) = delete;
42     PresenceService& operator=(PresenceService&&) = delete;
43     virtual ~PresenceService() = default;
44 
45     /**
46      * Clears any cached hardware presence data.
47      */
48     virtual void clearCache(void) = 0;
49 
50     /**
51      * Returns whether the hardware with the specified inventory path is
52      * present.
53      *
54      * May return a cached value if one is available to improve performance.
55      *
56      * Throws an exception if an error occurs while obtaining the presence
57      * value.
58      *
59      * @param inventoryPath D-Bus inventory path of the hardware
60      * @return true if hardware is present, false otherwise
61      */
62     virtual bool isPresent(const std::string& inventoryPath) = 0;
63 };
64 
65 /**
66  * @class DBusPresenceService
67  *
68  * Implementation of the PresenceService interface using D-Bus method calls.
69  */
70 class DBusPresenceService : public PresenceService
71 {
72   public:
73     // Specify which compiler-generated methods we want
74     DBusPresenceService() = delete;
75     DBusPresenceService(const DBusPresenceService&) = delete;
76     DBusPresenceService(DBusPresenceService&&) = delete;
77     DBusPresenceService& operator=(const DBusPresenceService&) = delete;
78     DBusPresenceService& operator=(DBusPresenceService&&) = delete;
79     virtual ~DBusPresenceService() = default;
80 
81     /**
82      * Constructor.
83      *
84      * @param bus D-Bus bus object
85      */
86     explicit DBusPresenceService(sdbusplus::bus_t& bus) : bus{bus} {}
87 
88     /** @copydoc PresenceService::clearCache() */
89     virtual void clearCache(void) override
90     {
91         cache.clear();
92     }
93 
94     /** @copydoc PresenceService::isPresent() */
95     virtual bool isPresent(const std::string& inventoryPath) override;
96 
97   private:
98     /**
99      * Returns whether the specified D-Bus exception is one of the expected
100      * types that can be thrown if hardware is not present.
101      *
102      * @return true if exception type is expected, false otherwise
103      */
104     bool isExpectedException(const sdbusplus::exception_t& e);
105 
106     /**
107      * D-Bus bus object.
108      */
109     sdbusplus::bus_t& bus;
110 
111     /**
112      * Cached presence data.
113      *
114      * Map from inventory paths to presence values.
115      */
116     std::map<std::string, bool> cache{};
117 };
118 
119 } // namespace phosphor::power::regulators
120