MQDescriptor.h revision b7370304cbf33a6ff53ec3955cda0bf18920df48 
1/*
2 * Copyright (C) 2016 The Android Open Source Project
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
17#ifndef _FMSGQ_DESCRIPTOR_H
18#define _FMSGQ_DESCRIPTOR_H
19
20#include <android-base/macros.h>
21#include <cutils/native_handle.h>
22#include <hidl/HidlInternal.h>
23#include <hidl/HidlSupport.h>
24#include <utils/Log.h>
25
26namespace android {
27namespace hardware {
28
29typedef uint64_t RingBufferPosition;
30
31struct GrantorDescriptor {
32    uint32_t flags __attribute__ ((aligned(4)));
33    uint32_t fdIndex __attribute__ ((aligned(4)));
34    uint32_t offset __attribute__ ((aligned(4)));
35    uint64_t extent __attribute__ ((aligned(8)));
36};
37
38static_assert(offsetof(GrantorDescriptor, flags) == 0, "wrong offset");
39static_assert(offsetof(GrantorDescriptor, fdIndex) == 4, "wrong offset");
40static_assert(offsetof(GrantorDescriptor, offset) == 8, "wrong offset");
41static_assert(offsetof(GrantorDescriptor, extent) == 16, "wrong offset");
42static_assert(sizeof(GrantorDescriptor) == 24, "wrong size");
43static_assert(__alignof(GrantorDescriptor) == 8, "wrong alignment");
44
45enum MQFlavor : uint32_t {
46  /*
47   * kSynchronizedReadWrite represents the wait-free synchronized flavor of the
48   * FMQ. It is intended to be have a single reader and single writer.
49   * Attempts to overflow/underflow returns a failure.
50   */
51  kSynchronizedReadWrite = 0x01,
52  /*
53   * kUnsynchronizedWrite represents the flavor of FMQ where writes always
54   * succeed. This flavor allows one writer and many readers. A read operation
55   * can detect an overwrite and reset the read counter.
56   */
57  kUnsynchronizedWrite = 0x02
58};
59
60template <typename T, MQFlavor flavor>
61struct MQDescriptor {
62    MQDescriptor(
63            const std::vector<GrantorDescriptor>& grantors,
64            native_handle_t* nHandle, size_t size);
65
66    MQDescriptor(size_t bufferSize, native_handle_t* nHandle,
67                 size_t messageSize, bool configureEventFlag = false);
68
69    MQDescriptor();
70    ~MQDescriptor();
71
72    explicit MQDescriptor(const MQDescriptor &other);
73    MQDescriptor &operator=(const MQDescriptor &other) = delete;
74
75    size_t getSize() const;
76
77    size_t getQuantum() const;
78
79    int32_t getFlags() const;
80
81    bool isHandleValid() const { return mHandle != nullptr; }
82    size_t countGrantors() const { return mGrantors.size(); }
83
84    inline const ::android::hardware::hidl_vec<GrantorDescriptor> &grantors() const {
85        return mGrantors;
86    }
87
88    inline ::android::hardware::hidl_vec<GrantorDescriptor> &grantors() {
89        return mGrantors;
90    }
91
92    inline const ::native_handle_t *handle() const {
93        return mHandle;
94    }
95
96    inline ::native_handle_t *handle() {
97        return mHandle;
98    }
99
100    static const size_t kOffsetOfGrantors;
101    static const size_t kOffsetOfHandle;
102    enum GrantorType : int { READPTRPOS = 0, WRITEPTRPOS, DATAPTRPOS, EVFLAGWORDPOS };
103
104    /*
105     * There should at least be GrantorDescriptors for the read counter, write
106     * counter and data buffer. A GrantorDescriptor for an EventFlag word is
107     * not required if there is no need for blocking FMQ operations.
108     */
109    static constexpr int32_t kMinGrantorCount = DATAPTRPOS + 1;
110
111    /*
112     * Minimum number of GrantorDescriptors required if EventFlag support is
113     * needed for blocking FMQ operations.
114     */
115    static constexpr int32_t kMinGrantorCountForEvFlagSupport = EVFLAGWORDPOS + 1;
116
117    //TODO(b/34160777) Identify a better solution that supports remoting.
118    static inline size_t alignToWordBoundary(size_t length) {
119        constexpr size_t kAlignmentSize = 64;
120        if (kAlignmentSize % __WORDSIZE != 0) {
121            details::logAlwaysFatal("Incompatible word size");
122        }
123        return (length + kAlignmentSize/8 - 1) & ~(kAlignmentSize/8 - 1U);
124    }
125
126    static inline size_t isAlignedToWordBoundary(size_t offset) {
127        constexpr size_t kAlignmentSize = 64;
128        return (offset & (kAlignmentSize/8 - 1)) == 0;
129    }
130private:
131    ::android::hardware::hidl_vec<GrantorDescriptor> mGrantors;
132    ::android::hardware::details::hidl_pointer<native_handle_t> mHandle;
133    uint32_t mQuantum;
134    uint32_t mFlags;
135};
136
137template<typename T, MQFlavor flavor>
138const size_t MQDescriptor<T, flavor>::kOffsetOfGrantors = offsetof(MQDescriptor, mGrantors);
139
140template<typename T, MQFlavor flavor>
141const size_t MQDescriptor<T, flavor>::kOffsetOfHandle = offsetof(MQDescriptor, mHandle);
142
143/*
144 * MQDescriptorSync will describe the wait-free synchronized
145 * flavor of FMQ.
146 */
147template<typename T>
148using MQDescriptorSync = MQDescriptor<T, kSynchronizedReadWrite>;
149
150/*
151 * MQDescriptorUnsync will describe the unsynchronized write
152 * flavor of FMQ.
153 */
154template<typename T>
155using MQDescriptorUnsync = MQDescriptor<T, kUnsynchronizedWrite>;
156
157template<typename T, MQFlavor flavor>
158MQDescriptor<T, flavor>::MQDescriptor(
159        const std::vector<GrantorDescriptor>& grantors,
160        native_handle_t* nhandle,
161        size_t size)
162    : mHandle(nhandle),
163      mQuantum(size),
164      mFlags(flavor) {
165    mGrantors.resize(grantors.size());
166    for (size_t i = 0; i < grantors.size(); ++i) {
167        if (isAlignedToWordBoundary(grantors[i].offset) == false) {
168            details::logAlwaysFatal("Grantor offsets need to be aligned");
169        }
170        mGrantors[i] = grantors[i];
171    }
172}
173
174template<typename T, MQFlavor flavor>
175MQDescriptor<T, flavor>::MQDescriptor(size_t bufferSize, native_handle_t *nHandle,
176                                   size_t messageSize, bool configureEventFlag)
177    : mHandle(nHandle), mQuantum(messageSize), mFlags(flavor) {
178    /*
179     * If configureEventFlag is true, allocate an additional spot in mGrantor
180     * for containing the fd and offset for mmapping the EventFlag word.
181     */
182    mGrantors.resize(configureEventFlag? kMinGrantorCountForEvFlagSupport : kMinGrantorCount);
183
184    size_t memSize[] = {
185        sizeof(RingBufferPosition),  /* memory to be allocated for read pointer counter */
186        sizeof(RingBufferPosition),  /* memory to be allocated for write pointer counter */
187        bufferSize,                  /* memory to be allocated for data buffer */
188        sizeof(std::atomic<uint32_t>)/* memory to be allocated for EventFlag word */
189    };
190
191    /*
192     * Create a default grantor descriptor for read, write pointers and
193     * the data buffer. fdIndex parameter is set to 0 by default and
194     * the offset for each grantor is contiguous.
195     */
196    for (size_t grantorPos = 0, offset = 0;
197         grantorPos < mGrantors.size();
198         offset += memSize[grantorPos++]) {
199        mGrantors[grantorPos] = {
200            0 /* grantor flags */,
201            0 /* fdIndex */,
202            static_cast<uint32_t>(alignToWordBoundary(offset)),
203            memSize[grantorPos]
204        };
205    }
206}
207
208template<typename T, MQFlavor flavor>
209MQDescriptor<T, flavor>::MQDescriptor(const MQDescriptor<T, flavor> &other)
210    : mGrantors(other.mGrantors),
211      mHandle(nullptr),
212      mQuantum(other.mQuantum),
213      mFlags(other.mFlags) {
214    if (other.mHandle != nullptr) {
215        mHandle = native_handle_create(
216                other.mHandle->numFds, other.mHandle->numInts);
217
218        for (int i = 0; i < other.mHandle->numFds; ++i) {
219            mHandle->data[i] = dup(other.mHandle->data[i]);
220        }
221
222        memcpy(&mHandle->data[other.mHandle->numFds],
223               &other.mHandle->data[other.mHandle->numFds],
224               other.mHandle->numInts * sizeof(int));
225    }
226}
227
228template<typename T, MQFlavor flavor>
229MQDescriptor<T, flavor>::MQDescriptor() : MQDescriptor(
230        std::vector<android::hardware::GrantorDescriptor>(),
231        nullptr /* nHandle */,
232        0 /* size */) {}
233
234template<typename T, MQFlavor flavor>
235MQDescriptor<T, flavor>::~MQDescriptor() {
236    if (mHandle != nullptr) {
237        native_handle_close(mHandle);
238        native_handle_delete(mHandle);
239    }
240}
241
242template<typename T, MQFlavor flavor>
243size_t MQDescriptor<T, flavor>::getSize() const {
244  return mGrantors[DATAPTRPOS].extent;
245}
246
247template<typename T, MQFlavor flavor>
248size_t MQDescriptor<T, flavor>::getQuantum() const { return mQuantum; }
249
250template<typename T, MQFlavor flavor>
251int32_t MQDescriptor<T, flavor>::getFlags() const { return mFlags; }
252
253template<typename T, MQFlavor flavor>
254std::string toString(const MQDescriptor<T, flavor> &q) {
255    std::string os;
256    if (flavor & kSynchronizedReadWrite) {
257        os += "fmq_sync";
258    }
259    if (flavor & kUnsynchronizedWrite) {
260        os += "fmq_unsync";
261    }
262    os += " {"
263       + toString(q.grantors().size()) + " grantor(s), "
264       + "size = " + toString(q.getSize())
265       + ", .handle = " + toString(q.handle())
266       + ", .quantum = " + toString(q.getQuantum()) + "}";
267    return os;
268}
269
270}  // namespace hardware
271}  // namespace android
272
273#endif  // FMSGQ_DESCRIPTOR_H
274