I2C.cpp

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/**
 * @file i2c.cpp
 *
 * Base class for devices attached via the I2C bus.
 *
 * @todo Bus frequency changes; currently we do nothing with the value
 *       that is supplied.  Should we just depend on the bus knowing?
 */

#include "I2C.hpp"

#include "dev_fs_lib_i2c.h"

namespace device
{

I2C::I2C(const char *name, const char *devname, const int bus, const uint16_t address, const uint32_t frequency) :
    CDev(name, devname)
{
    DEVICE_DEBUG("I2C::I2C name = %s devname = %s", name, devname);
    // fill in _device_id fields for a I2C device
    _device_id.devid_s.bus_type = DeviceBusType_I2C;
    _device_id.devid_s.bus = bus;
    _device_id.devid_s.address = address;
    // devtype needs to be filled in by the driver
    _device_id.devid_s.devtype = 0;
}

I2C::~I2C()
{
    if (_fd >= 0) {
        ::close(_fd);
        _fd = -1;
    }
}

int
I2C::init()
{
    // Assume the driver set the desired bus frequency. There is no standard
    // way to set it from user space.

    // do base class init, which will create device node, etc
    int ret = CDev::init();

    if (ret != PX4_OK) {
        DEVICE_DEBUG("CDev::init failed");
        return ret;
    }

    // Open the actual I2C device
    char dev_path[16];
    snprintf(dev_path, sizeof(dev_path), "/dev/iic-%i", get_device_bus());
    _fd = ::open(dev_path, O_RDWR);

    if (_fd < 0) {
        PX4_ERR("could not open %s", dev_path);
        px4_errno = errno;
        return PX4_ERROR;
    }

    return ret;
}

int
I2C::transfer(const uint8_t *send, const unsigned send_len, uint8_t *recv, const unsigned recv_len)
{
    dspal_i2c_ioctl_combined_write_read ioctl_write_read{};

    ioctl_write_read.write_buf = (uint8_t *)send;
    ioctl_write_read.write_buf_len = send_len;
    ioctl_write_read.read_buf = recv;
    ioctl_write_read.read_buf_len = recv_len;

    int bytes_read = ::ioctl(_fd, I2C_IOCTL_RDWR, &ioctl_write_read);

    if (bytes_read != (ssize_t)recv_len) {
        PX4_ERR("read register reports a read of %d bytes, but attempted to read %d bytes", bytes_read, recv_len);
        return -1;
    }

    return 0;
}

} // namespace device