source: rtems/cpukit/dev/i2c/fpga-i2c-slave.c

/*
 * Copyright (c) 2016-2017 Chris Johns <chrisj@rtems.org>
 * All rights reserved.
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rtems.org/license/LICENSE.
 */

/*
 * I2C slave for testing:
 *       https://github.com/oetr/FPGA-I2C-Slave
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <dev/i2c/i2c.h>
#include <dev/i2c/fpga-i2c-slave.h>

typedef struct {
  i2c_dev  base;
  uint16_t address;
  size_t   size;
} fpga_i2c_slave;

static ssize_t
fpga_i2c_slave_read(i2c_dev* base, void* buf, size_t n, off_t offset)
{
  fpga_i2c_slave* dev = (fpga_i2c_slave*) base;
  off_t           avail = dev->size - offset;
  uint8_t*        in = buf;
  size_t          todo;

  if (avail <= 0) {
    return 0;
  }

  if (n > avail) {
    n = (size_t) avail;
  }

  todo = n;

  while (todo > 0) {
    /*
     * Limit the transfer size so that it can be stored in 8-bits.  This may
     * help some bus controllers.
     */
    uint16_t cur = (uint16_t) (todo < 255 ?  todo : 255);
    i2c_msg msgs = {
      .addr = dev->base.address,
      .flags = I2C_M_RD,
      .buf = in,
      .len = cur
    };
    int err;
    err = i2c_bus_transfer(dev->base.bus, &msgs, 1);
    if (err != 0) {
      return err;
    }
    todo -= cur;
    in += cur;
  }

  return (ssize_t) n;
}

static ssize_t
fpga_i2c_slave_write(i2c_dev* base, const void* buf, size_t n, off_t offset)
{
  fpga_i2c_slave* dev = (fpga_i2c_slave*) base;
  off_t           avail = dev->size - offset;
  const uint8_t*  out = buf;
  size_t          todo;

  if (avail <= 0) {
    return 0;
  }

  if (n > avail) {
    n = (size_t) avail;
  }

  todo = n;

  while (todo > 0) {
    /*
     * Limit the transfer size so that it can be stored in 8-bits.  This may
     * help some bus controllers.
     */
    uint16_t cur = (uint16_t) (todo < 255 ?  todo : 255);
    i2c_msg msgs = {
      .addr = dev->base.address,
      .flags = 0,
      .buf = RTEMS_DECONST(uint8_t*, out),
      .len = cur
    };
    int err;
    err = i2c_bus_transfer(dev->base.bus, &msgs, 1);
    if (err != 0) {
      return err;
    }
    todo -= cur;
    out += cur;
  }

  return (ssize_t) n;
}

int
i2c_dev_register_fpga_i2c_slave(const char* bus_path,
                                const char* dev_path,
                                uint16_t    address,
                                size_t      size)

{
  fpga_i2c_slave* dev;

  dev = (fpga_i2c_slave*)
    i2c_dev_alloc_and_init(sizeof(*dev), bus_path, address);
  if (dev == NULL) {
    return -1;
  }

  dev->base.read = fpga_i2c_slave_read;
  dev->base.write = fpga_i2c_slave_write;
  dev->size = size;

  return i2c_dev_register(&dev->base, dev_path);
}