i2c.cc

#include "common/i2c.h"

#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>

#include <cassert>
#include <cstdio>
#include <stdexcept>

#include "common/swaglog.h"
#include "common/util.h"

#define UNUSED(x) (void)(x)

#ifdef QCOM2
// TODO: decide if we want to install libi2c-dev everywhere
extern "C" {
  #include <linux/i2c-dev.h>
  #include <i2c/smbus.h>
}

I2CBus::I2CBus(uint8_t bus_id) {
  char bus_name[20];
  snprintf(bus_name, 20, "/dev/i2c-%d", bus_id);

  i2c_fd = HANDLE_EINTR(open(bus_name, O_RDWR));
  if (i2c_fd < 0) {
    throw std::runtime_error("Failed to open I2C bus");
  }
}

I2CBus::~I2CBus() {
  if (i2c_fd >= 0) {
    close(i2c_fd);
  }
}

int I2CBus::read_register(uint8_t device_address, uint register_address, uint8_t *buffer, uint8_t len) {
  std::lock_guard lk(m);

  int ret = 0;

  ret = HANDLE_EINTR(ioctl(i2c_fd, I2C_SLAVE, device_address));
  if (ret < 0) { goto fail; }

  ret = i2c_smbus_read_i2c_block_data(i2c_fd, register_address, len, buffer);
  if ((ret < 0) || (ret != len)) { goto fail; }

fail:
  return ret;
}

int I2CBus::set_register(uint8_t device_address, uint register_address, uint8_t data) {
  std::lock_guard lk(m);

  int ret = 0;

  ret = HANDLE_EINTR(ioctl(i2c_fd, I2C_SLAVE, device_address));
  if (ret < 0) { goto fail; }

  ret = i2c_smbus_write_byte_data(i2c_fd, register_address, data);
  if (ret < 0) { goto fail; }

fail:
  return ret;
}

#else

I2CBus::I2CBus(uint8_t bus_id) {
  UNUSED(bus_id);
  i2c_fd = -1;
}

I2CBus::~I2CBus() {}

int I2CBus::read_register(uint8_t device_address, uint register_address, uint8_t *buffer, uint8_t len) {
  UNUSED(device_address);
  UNUSED(register_address);
  UNUSED(buffer);
  UNUSED(len);
  return -1;
}

int I2CBus::set_register(uint8_t device_address, uint register_address, uint8_t data) {
  UNUSED(device_address);
  UNUSED(register_address);
  UNUSED(data);
  return -1;
}
#endif