px4_autopilot/apps/drivers/device/i2c.cpp

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/**
 * @file 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.h"

namespace device
{

I2C::I2C(const char *name,
	 const char *devname,
	 int bus,
	 uint16_t address,
	 uint32_t frequency,
	 int irq) :
	// base class
	CDev(name, devname, irq),
	// public
	// protected
	// private
	_bus(bus),
	_address(address),
	_frequency(frequency),
	_dev(nullptr)
{
}

I2C::~I2C()
{
	if (_dev)
		up_i2cuninitialize(_dev);
}

int
I2C::init()
{
	int ret = OK;

	// attach to the i2c bus
	_dev = up_i2cinitialize(_bus);

	if (_dev == nullptr) {
		debug("failed to init I2C");
		ret = -ENOENT;
		goto out;
	}

	// call the probe function to check whether the device is present
	ret = probe();

	if (ret != OK) {
		debug("probe failed");
		goto out;
	}

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

	if (ret != OK) {
		debug("cdev init failed");
		goto out;
	}

	// tell the world where we are
	log("on bus %d at 0x%02x", _bus, _address);

out:
	return ret;
}

int
I2C::probe()
{
	// Assume the device is too stupid to be discoverable.
	return OK;
}

int
I2C::transfer(uint8_t *send, unsigned send_len, uint8_t *recv, unsigned recv_len)
{
	struct i2c_msg_s msgv[2];
	unsigned msgs;
	int ret;

//	debug("transfer out %p/%u  in %p/%u", send, send_len, recv, recv_len);

	msgs = 0;

	if (send_len > 0) {
		msgv[msgs].addr = _address;
		msgv[msgs].flags = 0;
		msgv[msgs].buffer = send;
		msgv[msgs].length = send_len;
		msgs++;
	}

	if (recv_len > 0) {
		msgv[msgs].addr = _address;
		msgv[msgs].flags = I2C_M_READ;
		msgv[msgs].buffer = recv;
		msgv[msgs].length = recv_len;
		msgs++;
	}

	if (msgs == 0)
		return -EINVAL;

	ret = I2C_TRANSFER(_dev, &msgv[0], msgs);

	return ret;
}

} // namespace device