nuttx/drivers/i2c/i2c_read.c

/****************************************************************************
 * drivers/i2c/i2c_read.c
 *
 *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <assert.h>

#include <nuttx/i2c/i2c_master.h>

#if defined(CONFIG_I2C_TRANSFER)

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: i2c_read
 *
 * Description:
 *   Receive a block of data from I2C using the previously selected I2C
 *   frequency and slave address. Each read operational will be an 'atomic'
 *   operation in the sense that any other I2C actions will be serialized
 *   and pend until this read completes. Required.
 *
 * Input Parameters:
 *   dev    - Device-specific state data
 *   buffer - A pointer to a buffer of data to receive the data from the device
 *   buflen - The requested number of bytes to be read
 *
 * Returned Value:
 *   0: success, <0: A negated errno
 *
 ****************************************************************************/

int i2c_read(FAR struct i2c_dev_s *dev, FAR const struct i2c_config_s *config,
             FAR uint8_t *buffer, int buflen)
{
  struct i2c_msg_s msg;
  unsigned int flags;

  /* 7- or 10-bit? */

  flags = (config->addrlen == 10) ? I2C_M_TEN : 0;

  /* Setup for the transfer */

  msg.addr   = config->address,
  msg.flags  = (flags | I2C_M_READ);
  msg.buffer = buffer;
  msg.length = buflen;

  /* Then perform the transfer
   *
   * REVISIT:  The following two operations must become atomic in order to
   * assure thread safety.
   */

  I2C_SETFREQUENCY(dev, config->frequency);
  return I2C_TRANSFER(dev, &msg, 1);
}

#endif /* CONFIG_I2C_TRANSFER */