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