initiator.h

// Copyright 2021 The Pigweed Authors
//
// 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
//
//     https://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 <cstdint>
#include <type_traits>
 
#include "pw_assert/assert.h"
#include "pw_bytes/span.h"
#include "pw_status/status.h"
 
namespace pw::spi {
 
 
enum class ClockPolarity : uint8_t {
  kActiveHigh,  // Corresponds to CPOL = 0
  kActiveLow,   // Corresponds to CPOL = 1
};
 
enum class ClockPhase : uint8_t {
  kRisingEdge,   // Corresponds to CPHA = 0
  kFallingEdge,  // Corresponds to CPHA = 1
};
 
enum class BitOrder : uint8_t {
  kLsbFirst,
  kMsbFirst,
};
 
class BitsPerWord {
 public:
  constexpr BitsPerWord(uint8_t data_bits) : data_bits_(data_bits) {
    PW_ASSERT(data_bits_ >= 3 && data_bits_ <= 32);
  }
 
  constexpr uint8_t operator()() const { return data_bits_; }
 
 private:
  uint8_t data_bits_;
};
 
struct Config {
  ClockPolarity polarity;
  ClockPhase phase;
  BitsPerWord bits_per_word;
  BitOrder bit_order;
 
  constexpr bool operator==(const Config& rhs) const {
    return polarity == rhs.polarity && phase == rhs.phase &&
           bits_per_word() == rhs.bits_per_word() && bit_order == rhs.bit_order;
  }
 
  constexpr bool operator!=(const Config& rhs) const { return !(*this == rhs); }
};
static_assert(sizeof(Config) == sizeof(uint32_t),
              "Ensure that the config struct fits in 32-bits");
 
// inclusive-language: disable
// inclusive-language: enable
class Initiator {
 public:
  virtual ~Initiator() = default;
 
  Status Configure(const Config& config) { return DoConfigure(config); }
 
  Status WriteRead(ConstByteSpan write_buffer, ByteSpan read_buffer) {
    return DoWriteRead(write_buffer, read_buffer);
  }
 
 private:
  // Subclass API:
  virtual Status DoConfigure(const Config& config) = 0;
  virtual Status DoWriteRead(ConstByteSpan write_buffer,
                             ByteSpan read_buffer) = 0;
};
 
 
}  // namespace pw::spi