common/brillo_i2c/src/i2c_service/i2c_device.h

// 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.

// Defines a single i2c device at an address for a named i2c bus.
//
// Can be used to read and write i2c registers, or send arbitrary streams of
// messages.


#include <fcntl.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>
#include <android-base/logging.h>


class I2CDevice {

 public:
  // Creates an I2CDevice for a given filename and address.
  //
  // For example: I2CDevice my_device("/dev/i2c-0", 0x20);
  //
  // Note: this constructor does not actually open the device, Begin() must be
  // called at the appropriate time.
  I2CDevice(const char* device_filename,
            const uint8_t device_address);
  // Opens the device for reading and writing. Returns 0 on success, or the
  // error code from the open/ioctl operations.
  int Begin();
  // Closes the device. Returns 0 on success or the error code from the close
  // operation.
  int End();
  // Sends a sequence of I2C messages. This is used for write operations AND
  // read operations, since reads are just an empty outbound message. Returns 0
  // on success or the error code from the ioctl operation.
  int Send(struct i2c_msg messages[],
           const size_t count);
  // Sets a register at a given address to a given value. Returns 0 on success
  // or the error code from the ioctl operation.
  int SetRegister(const uint8_t register_address,
                  const uint8_t value);
  // Reads a register into a passed value. Returns 0 on success or the error
  // code from the ioctl operation.
  int GetRegister(const uint8_t register_address,
                  uint8_t& value);

 private:
  // Demonstrates opening a device.
  int open_i2c();
  // Demonstrates sending the I2C_SLAVE ioctl.
  int enslave_i2c();

  // Stores the device address.
  const uint8_t address_;
  // Stores the device filename.
  const char* filename_;
  // Stores the open file descriptor for the device.
  int fd_;
};