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/*
* Copyright (C) 2020 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.
*/
#pragma once
#include <assert.h>
#include <string>
namespace android {
namespace hardware {
enum MQFlavor : uint32_t {
/*
* kSynchronizedReadWrite represents the wait-free synchronized flavor of the
* FMQ. It is intended to be have a single reader and single writer.
* Attempts to overflow/underflow returns a failure.
*/
kSynchronizedReadWrite = 0x01,
/*
* kUnsynchronizedWrite represents the flavor of FMQ where writes always
* succeed. This flavor allows one writer and many readers. A read operation
* can detect an overwrite and reset the read counter.
*/
kUnsynchronizedWrite = 0x02
};
struct GrantorDescriptor {
uint32_t flags __attribute__((aligned(4)));
uint32_t fdIndex __attribute__((aligned(4)));
uint32_t offset __attribute__((aligned(4)));
uint64_t extent __attribute__((aligned(8)));
};
static_assert(offsetof(GrantorDescriptor, flags) == 0, "wrong offset");
static_assert(offsetof(GrantorDescriptor, fdIndex) == 4, "wrong offset");
static_assert(offsetof(GrantorDescriptor, offset) == 8, "wrong offset");
static_assert(offsetof(GrantorDescriptor, extent) == 16, "wrong offset");
static_assert(sizeof(GrantorDescriptor) == 24, "wrong size");
static_assert(__alignof(GrantorDescriptor) == 8, "wrong alignment");
namespace details {
void logError(const std::string& message);
void errorWriteLog(int tag, const char* message);
void check(bool exp, const char* message);
typedef uint64_t RingBufferPosition;
enum GrantorType : int { READPTRPOS = 0, WRITEPTRPOS, DATAPTRPOS, EVFLAGWORDPOS };
/*
* There should at least be GrantorDescriptors for the read counter, write
* counter and data buffer. A GrantorDescriptor for an EventFlag word is
* not required if there is no need for blocking FMQ operations.
*/
static constexpr int32_t kMinGrantorCount = DATAPTRPOS + 1;
/*
* Minimum number of GrantorDescriptors required if EventFlag support is
* needed for blocking FMQ operations.
*/
static constexpr int32_t kMinGrantorCountForEvFlagSupport = EVFLAGWORDPOS + 1;
static inline size_t alignToWordBoundary(size_t length) {
constexpr size_t kAlignmentSize = 64;
static_assert(kAlignmentSize % sizeof(long) == 0, "Incompatible word size");
/*
* Check if alignment to word boundary would cause an overflow.
*/
check(length <= SIZE_MAX - kAlignmentSize / 8 + 1, "Queue size too large");
return (length + kAlignmentSize / 8 - 1) & ~(kAlignmentSize / 8 - 1U);
}
static inline size_t isAlignedToWordBoundary(size_t offset) {
constexpr size_t kAlignmentSize = 64;
return (offset & (kAlignmentSize / 8 - 1)) == 0;
}
} // namespace details
} // namespace hardware
} // namespace android