1 /* 2 // Copyright (c) 2022 Equinix, Inc. 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 #pragma once 18 19 #include <cstdint> 20 #include <cstdio> 21 #include <functional> 22 #include <map> 23 #include <optional> 24 #include <utility> 25 26 extern "C" 27 { 28 // For I2C_SMBUS_BLOCK_MAX 29 #include <linux/i2c.h> 30 } 31 32 // A function to read up to I2C_SMBUS_BLOCK_MAX bytes of FRU data. Returns 33 // negative on error, or the number of bytes read otherwise, which may be (but 34 // is not guaranteed to be) less than len if the read would go beyond the end 35 // of the FRU. 36 using ReadBlockFunc = 37 std::function<int64_t(off_t offset, size_t len, uint8_t* outbuf)>; 38 39 // A caching wrapper around a ReadBlockFunc 40 class FRUReader 41 { 42 public: FRUReader(ReadBlockFunc readFunc)43 explicit FRUReader(ReadBlockFunc readFunc) : readFunc(std::move(readFunc)) 44 {} 45 // The ::read() operation here is analogous to ReadBlockFunc (with the same 46 // return value semantics), but is not subject to SMBus block size 47 // limitations; it can read as much data as needed in a single call. 48 ssize_t read(off_t start, size_t len, uint8_t* outbuf); 49 50 private: 51 static constexpr size_t cacheBlockSize = 32; 52 static_assert(cacheBlockSize <= I2C_SMBUS_BLOCK_MAX); 53 using CacheBlock = std::array<uint8_t, cacheBlockSize>; 54 55 // indexed by block number (byte number / block size) 56 using Cache = std::map<uint32_t, CacheBlock>; 57 58 ReadBlockFunc readFunc; 59 Cache cache; 60 61 // byte offset of the end of the FRU (if readFunc has reported it) 62 std::optional<size_t> eof; 63 }; 64