common/brillo_i2c/src/i2c_service/i2c_device.cpp

// Copyright 2015 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.


#include "i2c_device.h"

I2CDevice::I2CDevice(const char* device_filename,
                     const uint8_t device_address) :
  // Does nothing except store the constant values.
  address_(device_address),
  filename_(device_filename)

  {
    LOG(INFO) << "New i2c device for " << address_ << " at " << filename_;
  }


int I2CDevice::Begin() {
  // First, this opens the /dev device.
  int rc = open_i2c();
  if (rc < 0) {
    return rc;
  }
  // Then, registers it as a slave.
  rc = enslave_i2c();
  if (rc < 0) {
    return rc;
  }
  return 0;
}


int I2CDevice::End() {
  return close(fd_);
}


int I2CDevice::open_i2c() {
  // Opening the device is just a R/W file open.
  int fd = open(filename_, O_RDWR);
  if (-1 == fd) {
    PLOG(ERROR) << "Could not open i2c device.";
    return -1;
  }
  LOG(INFO) << "i2c device opened at " << filename_;
  fd_ = fd;
  return fd;
}


int I2CDevice::enslave_i2c() {
  // The I2C_SLAVE ioctl is sent to the device at the given address.
  int rc = ioctl(fd_, I2C_SLAVE, address_);
  if (rc < 0) {
    PLOG(ERROR) << "i2c device failed to become a slave.";
    return rc;
  }
  printf("yes %x\n", address_);
  LOG(INFO) << "i2c device is a slave at" << filename_;
  return rc;
}


int I2CDevice::Send(struct i2c_msg messages[],
                    const size_t count) {
  // Sending messages requires them to be wrapped in the i2c_rdwr_ioctl_data
  // struct and sending them using the I2C_RDWR ioctl.
  struct i2c_rdwr_ioctl_data data = {
    .msgs = messages,
    .nmsgs = count
  };
  int rc = ioctl(fd_, I2C_RDWR, &data);
  if (rc < 0) {
    PLOG(ERROR) << "Unable to send data.";
  }
  return rc;
}


int I2CDevice::SetRegister(const uint8_t register_address,
                           const uint8_t value) {
  // Setting a register involves sending a single message with a 2-byte payload.
  // The first byte is the register address, and the second is the value.
  uint8_t outbuf[] = {register_address, value};
  struct i2c_msg messages[1];
  messages[0] = {
    .addr = address_,
    .flags = 0,
    .len = sizeof(outbuf),
    .buf = outbuf
  };
  return Send(messages, 1);
}


int I2CDevice::GetRegister(const uint8_t register_address,
                           uint8_t& value) {
  // Reading a register involves sending two messages, each with a single-byte
  // payload. The first message contains the register address and the second
  // message is empty and will contain the response value.
  struct i2c_msg messages[2];
  uint8_t outbuf = register_address;
  // Both messages need the addr value set.
  messages[0] = {
    .addr = address_,
    .flags = 0,
    .len = 1,
    .buf = &outbuf
  };
  // Needs to pass the I2C_M_RD flag in order to get the value.
  messages[1] = {
    .addr = address_,
    .flags = I2C_M_RD,
    .len = 1,
    .buf = &value,
  };
  // Will contain the register value.
  int rc = Send(messages, 2);
  return rc;
}