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"

#ifdef __PX4_LINUX

#include <linux/i2c.h>
#include <linux/i2c-dev.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/i2c-%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)
{
    struct i2c_msg msgv[2];
    unsigned msgs;
    int ret = PX4_ERROR;
    unsigned retry_count = 0;

    if (_fd < 0) {
        PX4_ERR("I2C device not opened");
        return 1;
    }

    do {
        DEVICE_DEBUG("transfer out %p/%u  in %p/%u", send, send_len, recv, recv_len);
        msgs = 0;

        if (send_len > 0) {
            msgv[msgs].addr = get_device_address();
            msgv[msgs].flags = 0;
            msgv[msgs].buf = const_cast<uint8_t *>(send);
            msgv[msgs].len = send_len;
            msgs++;
        }

        if (recv_len > 0) {
            msgv[msgs].addr = get_device_address();
            msgv[msgs].flags = I2C_M_READ;
            msgv[msgs].buf = recv;
            msgv[msgs].len = recv_len;
            msgs++;
        }

        if (msgs == 0) {
            return -EINVAL;
        }

        struct i2c_rdwr_ioctl_data packets;

        packets.msgs  = msgv;

        packets.nmsgs = msgs;

        ret = ::ioctl(_fd, I2C_RDWR, (unsigned long)&packets);

        if (ret == -1) {
            DEVICE_DEBUG("I2C transfer failed");
            ret = PX4_ERROR;

        } else {
            ret = PX4_OK;
        }

        /* success */
        if (ret == PX4_OK) {
            break;
        }

    } while (retry_count++ < _retries);

    return ret;
}

} // namespace device

#endif // __PX4_LINUX