1 // SPDX-License-Identifier: Apache-2.0 2 // SPDX-FileCopyrightText: Copyright 2022 Equinix, Inc. 3 4 #pragma once 5 6 #include <cstdint> 7 #include <cstdio> 8 #include <functional> 9 #include <map> 10 #include <optional> 11 #include <utility> 12 13 extern "C" 14 { 15 // For I2C_SMBUS_BLOCK_MAX 16 #include <linux/i2c.h> 17 } 18 19 // A function to read up to I2C_SMBUS_BLOCK_MAX bytes of FRU data. Returns 20 // negative on error, or the number of bytes read otherwise, which may be (but 21 // is not guaranteed to be) less than len if the read would go beyond the end 22 // of the FRU. 23 using ReadBlockFunc = 24 std::function<int64_t(off_t offset, size_t len, uint8_t* outbuf)>; 25 26 // A caching wrapper around a ReadBlockFunc 27 class FRUReader 28 { 29 public: FRUReader(ReadBlockFunc readFunc)30 explicit FRUReader(ReadBlockFunc readFunc) : readFunc(std::move(readFunc)) 31 {} 32 // The ::read() operation here is analogous to ReadBlockFunc (with the same 33 // return value semantics), but is not subject to SMBus block size 34 // limitations; it can read as much data as needed in a single call. 35 ssize_t read(off_t start, size_t len, uint8_t* outbuf); 36 37 private: 38 static constexpr size_t cacheBlockSize = 32; 39 static_assert(cacheBlockSize <= I2C_SMBUS_BLOCK_MAX); 40 using CacheBlock = std::array<uint8_t, cacheBlockSize>; 41 42 // indexed by block number (byte number / block size) 43 using Cache = std::map<uint32_t, CacheBlock>; 44 45 ReadBlockFunc readFunc; 46 Cache cache; 47 48 // byte offset of the end of the FRU (if readFunc has reported it) 49 std::optional<size_t> eof; 50 }; 51