PX4-Autopilot/src/drivers/device/posix/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>
#endif

#ifdef __PX4_QURT
#define PX4_SIMULATE_I2C 1
#else
#define PX4_SIMULATE_I2C 0
#endif

static constexpr const int simulate = PX4_SIMULATE_I2C;


namespace device
{

I2C::I2C(const char *name, const char *devname, int bus, uint16_t address, 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) {
#ifndef __PX4_QURT
		::close(_fd);
#endif /* !__PX4_QURT */
		_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;
	}

	if (simulate) {
		_fd = 10000;

	} else {
#ifndef __PX4_QURT

		// 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;
		}

#endif /* !__PX4_QURT */
	}

	return ret;
}

int
I2C::transfer(const uint8_t *send, unsigned send_len, uint8_t *recv, unsigned recv_len)
{
#ifndef __PX4_LINUX
	return PX4_ERROR;
#else
	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;

		if (simulate) {
			DEVICE_DEBUG("I2C SIM: transfer_4 on %s", get_devname());
			ret = PX4_OK;

		} else {
			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;
#endif
}

} // namespace device