peripheral/libmraa/src/spi/spi.c - platform/hardware/bsp/intel - Git at Google

 /*
  * Author: Thomas Ingleby <thomas.c.ingleby@intel.com>
  * Author: Brendan Le Foll <brendan.le.foll@intel.com>
  * Copyright (c) 2014, 2015 Intel Corporation.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
  * "Software"), to deal in the Software without restriction, including
  * without limitation the rights to use, copy, modify, merge, publish,
  * distribute, sublicense, and/or sell copies of the Software, and to
  * permit persons to whom the Software is furnished to do so, subject to
  * the following conditions:
  *
  * The above copyright notice and this permission notice shall be
  * included in all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */

 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <linux/spi/spidev.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <unistd.h>

 #include "spi.h"
 #include "mraa_internal.h"

 #define MAX_SIZE 64
 #define SPI_MAX_LENGTH 4096

 static mraa_spi_context
 mraa_spi_init_internal(mraa_adv_func_t* func_table)
 {
     mraa_spi_context dev = (mraa_spi_context) calloc(1, sizeof(struct _spi));
     if (dev == NULL) {
         return NULL;
     }
     dev->advance_func = func_table;

     return dev;
 }

 mraa_spi_context
 mraa_spi_init(int bus)
 {
     if (plat == NULL) {
         syslog(LOG_ERR, "spi: Platform Not Initialised");
         return NULL;
     }
     if (mraa_is_sub_platform_id(bus)) {
         syslog(LOG_ERR, "spi: Spi module doesn't support subplatforms");
         return NULL;
     }
     if (plat->spi_bus_count == 0) {
         syslog(LOG_ERR, "spi: no spi buses defined in platform");
         return NULL;
     }
     if (plat->spi_bus_count == 1) {
         bus = plat->def_spi_bus;
     }
     if (bus >= plat->spi_bus_count) {
         syslog(LOG_ERR, "spi: requested bus above spi bus count");
         return NULL;
     }
     if (plat->adv_func->spi_init_pre != NULL) {
         if (plat->adv_func->spi_init_pre(bus) != MRAA_SUCCESS) {
             return NULL;
         }
     }

     if (!plat->no_bus_mux) {
         int pos = plat->spi_bus[bus].sclk;
         if (plat->pins[pos].spi.mux_total > 0) {
             if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
                 syslog(LOG_ERR, "spi: failed to set-up spi sclk multiplexer");
                 return NULL;
             }
         }

         pos = plat->spi_bus[bus].mosi;
         if (plat->pins[pos].spi.mux_total > 0) {
             if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
                 syslog(LOG_ERR, "spi: failed to set-up spi mosi multiplexer");
                 return NULL;
             }
         }

         pos = plat->spi_bus[bus].miso;
         if (plat->pins[pos].spi.mux_total > 0) {
             if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
                 syslog(LOG_ERR, "spi: failed to set-up spi miso multiplexer");
                 return NULL;
             }
         }

         pos = plat->spi_bus[bus].cs;
         if (plat->pins[pos].spi.mux_total > 0) {
             if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
                 syslog(LOG_ERR, "spi: failed to set-up spi cs multiplexer");
                 return NULL;
             }
         }
     }
     mraa_spi_context dev = mraa_spi_init_raw(plat->spi_bus[bus].bus_id, plat->spi_bus[bus].slave_s);

     if (plat->adv_func->spi_init_post != NULL) {
         mraa_result_t ret = plat->adv_func->spi_init_post(dev);
         if (ret != MRAA_SUCCESS) {
             free(dev);
             return NULL;
         }
     }

     return dev;
 }

 mraa_spi_context
 mraa_spi_init_raw(unsigned int bus, unsigned int cs)
 {
     mraa_spi_context dev = mraa_spi_init_internal(plat == NULL ? NULL : plat->adv_func);
     if (dev == NULL) {
         syslog(LOG_CRIT, "spi: Failed to allocate memory for context");
         return NULL;
     }

     char path[MAX_SIZE];
     sprintf(path, "/dev/spidev%u.%u", bus, cs);

     dev->devfd = open(path, O_RDWR);
     if (dev->devfd < 0) {
         syslog(LOG_ERR, "spi: Failed opening SPI Device. bus:%s", path);
         free(dev);
         return NULL;
     }

     int speed = 0;
     if (ioctl(dev->devfd, SPI_IOC_RD_MAX_SPEED_HZ, &speed) != -1) {
         dev->clock = speed;
     } else {
         // We had this on Galileo Gen1, so let it be a fallback value
         dev->clock = 4000000;
         syslog(LOG_WARNING, "spi: Max speed query failed, setting %d", dev->clock);
     }

     if (mraa_spi_mode(dev, MRAA_SPI_MODE0) != MRAA_SUCCESS) {
         free(dev);
         return NULL;
     }

     if (mraa_spi_lsbmode(dev, 0) != MRAA_SUCCESS) {
         free(dev);
         return NULL;
     }

     if (mraa_spi_bit_per_word(dev, 8) != MRAA_SUCCESS) {
         free(dev);
         return NULL;
     }

     return dev;
 }

 mraa_result_t
 mraa_spi_mode(mraa_spi_context dev, mraa_spi_mode_t mode)
 {
     uint8_t spi_mode = 0;
     switch (mode) {
         case MRAA_SPI_MODE0:
             spi_mode = SPI_MODE_0;
             break;
         case MRAA_SPI_MODE1:
             spi_mode = SPI_MODE_1;
             break;
         case MRAA_SPI_MODE2:
             spi_mode = SPI_MODE_2;
             break;
         case MRAA_SPI_MODE3:
             spi_mode = SPI_MODE_3;
             break;
         default:
             spi_mode = SPI_MODE_0;
             break;
     }

     if (ioctl(dev->devfd, SPI_IOC_WR_MODE, &spi_mode) < 0) {
         syslog(LOG_ERR, "spi: Failed to set spi mode");
         return MRAA_ERROR_INVALID_RESOURCE;
     }

     dev->mode = spi_mode;
     return MRAA_SUCCESS;
 }

 mraa_result_t
 mraa_spi_frequency(mraa_spi_context dev, int hz)
 {
     int speed = 0;
     dev->clock = hz;
     if (ioctl(dev->devfd, SPI_IOC_RD_MAX_SPEED_HZ, &speed) != -1) {
         if (speed < hz) {
             dev->clock = speed;
             syslog(LOG_WARNING, "spi: Selected speed reduced to max allowed speed");
         }
     }
     return MRAA_SUCCESS;
 }

 mraa_result_t
 mraa_spi_lsbmode(mraa_spi_context dev, mraa_boolean_t lsb)
 {
     if (IS_FUNC_DEFINED(dev, spi_lsbmode_replace)) {
         return dev->advance_func->spi_lsbmode_replace(dev, lsb);
     }

     uint8_t lsb_mode = (uint8_t) lsb;
     if (ioctl(dev->devfd, SPI_IOC_WR_LSB_FIRST, &lsb_mode) < 0) {
         syslog(LOG_ERR, "spi: Failed to set bit order");
         return MRAA_ERROR_INVALID_RESOURCE;
     }
     if (ioctl(dev->devfd, SPI_IOC_RD_LSB_FIRST, &lsb_mode) < 0) {
         syslog(LOG_ERR, "spi: Failed to set bit order");
         return MRAA_ERROR_INVALID_RESOURCE;
     }
     dev->lsb = lsb;
     return MRAA_SUCCESS;
 }

 mraa_result_t
 mraa_spi_bit_per_word(mraa_spi_context dev, unsigned int bits)
 {
     if (ioctl(dev->devfd, SPI_IOC_WR_BITS_PER_WORD, &bits) < 0) {
         syslog(LOG_ERR, "spi: Failed to set bit per word");
         return MRAA_ERROR_INVALID_RESOURCE;
     }
     dev->bpw = bits;
     return MRAA_SUCCESS;
 }

 int
 mraa_spi_write(mraa_spi_context dev, uint8_t data)
 {
     struct spi_ioc_transfer msg;
     memset(&msg, 0, sizeof(msg));

     uint16_t length = 1;

     unsigned long recv = 0;
     msg.tx_buf = (unsigned long) &data;
     msg.rx_buf = (unsigned long) &recv;
     msg.speed_hz = dev->clock;
     msg.bits_per_word = dev->bpw;
     msg.delay_usecs = 0;
     msg.len = length;
     if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
         syslog(LOG_ERR, "spi: Failed to perform dev transfer");
         return -1;
     }
     return (int) recv;
 }

 int
 mraa_spi_write_word(mraa_spi_context dev, uint16_t data)
 {
     struct spi_ioc_transfer msg;
     memset(&msg, 0, sizeof(msg));

     uint16_t length = 2;

     uint16_t recv = 0;
     msg.tx_buf = (unsigned long) &data;
     msg.rx_buf = (unsigned long) &recv;
     msg.speed_hz = dev->clock;
     msg.bits_per_word = dev->bpw;
     msg.delay_usecs = 0;
     msg.len = length;
     if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
         syslog(LOG_ERR, "spi: Failed to perform dev transfer");
         return -1;
     }
     return (int) recv;
 }

 mraa_result_t
 mraa_spi_transfer_buf(mraa_spi_context dev, uint8_t* data, uint8_t* rxbuf, int length)
 {
     struct spi_ioc_transfer msg;
     memset(&msg, 0, sizeof(msg));

     msg.tx_buf = (unsigned long) data;
     msg.rx_buf = (unsigned long) rxbuf;
     msg.speed_hz = dev->clock;
     msg.bits_per_word = dev->bpw;
     msg.delay_usecs = 0;
     msg.len = length;
     if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
         syslog(LOG_ERR, "spi: Failed to perform dev transfer");
         return MRAA_ERROR_INVALID_RESOURCE;
     }
     return MRAA_SUCCESS;
 }

 mraa_result_t
 mraa_spi_transfer_buf_word(mraa_spi_context dev, uint16_t* data, uint16_t* rxbuf, int length)
 {
     struct spi_ioc_transfer msg;
     memset(&msg, 0, sizeof(msg));

     msg.tx_buf = (unsigned long) data;
     msg.rx_buf = (unsigned long) rxbuf;
     msg.speed_hz = dev->clock;
     msg.bits_per_word = dev->bpw;
     msg.delay_usecs = 0;
     msg.len = length;
     if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
         syslog(LOG_ERR, "spi: Failed to perform dev transfer");
         return MRAA_ERROR_INVALID_RESOURCE;
     }
     return MRAA_SUCCESS;
 }

 uint8_t*
 mraa_spi_write_buf(mraa_spi_context dev, uint8_t* data, int length)
 {
     uint8_t* recv = malloc(sizeof(uint8_t) * length);

     if (mraa_spi_transfer_buf(dev, data, recv, length) != MRAA_SUCCESS) {
         free(recv);
         return NULL;
     }
     return recv;
 }

 uint16_t*
 mraa_spi_write_buf_word(mraa_spi_context dev, uint16_t* data, int length)
 {
     uint16_t* recv = malloc(sizeof(uint16_t) * length);

     if (mraa_spi_transfer_buf_word(dev, data, recv, length) != MRAA_SUCCESS) {
         free(recv);
         return NULL;
     }
     return recv;
 }

 mraa_result_t
 mraa_spi_stop(mraa_spi_context dev)
 {
     close(dev->devfd);
     free(dev);
     return MRAA_SUCCESS;
 }
	/*
	* Author: Thomas Ingleby <thomas.c.ingleby@intel.com>
	* Author: Brendan Le Foll <brendan.le.foll@intel.com>
	* Copyright (c) 2014, 2015 Intel Corporation.
	*
	* Permission is hereby granted, free of charge, to any person obtaining
	* a copy of this software and associated documentation files (the
	* "Software"), to deal in the Software without restriction, including
	* without limitation the rights to use, copy, modify, merge, publish,
	* distribute, sublicense, and/or sell copies of the Software, and to
	* permit persons to whom the Software is furnished to do so, subject to
	* the following conditions:
	*
	* The above copyright notice and this permission notice shall be
	* included in all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
	* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
	* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
	* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
	*/

	#include <stdlib.h>
	#include <string.h>
	#include <sys/ioctl.h>
	#include <linux/spi/spidev.h>
	#include <stdio.h>
	#include <fcntl.h>
	#include <unistd.h>

	#include "spi.h"
	#include "mraa_internal.h"

	#define MAX_SIZE 64
	#define SPI_MAX_LENGTH 4096

	static mraa_spi_context
	mraa_spi_init_internal(mraa_adv_func_t* func_table)
	{
	mraa_spi_context dev = (mraa_spi_context) calloc(1, sizeof(struct _spi));
	if (dev == NULL) {
	return NULL;
	}
	dev->advance_func = func_table;

	return dev;
	}

	mraa_spi_context
	mraa_spi_init(int bus)
	{
	if (plat == NULL) {
	syslog(LOG_ERR, "spi: Platform Not Initialised");
	return NULL;
	}
	if (mraa_is_sub_platform_id(bus)) {
	syslog(LOG_ERR, "spi: Spi module doesn't support subplatforms");
	return NULL;
	}
	if (plat->spi_bus_count == 0) {
	syslog(LOG_ERR, "spi: no spi buses defined in platform");
	return NULL;
	}
	if (plat->spi_bus_count == 1) {
	bus = plat->def_spi_bus;
	}
	if (bus >= plat->spi_bus_count) {
	syslog(LOG_ERR, "spi: requested bus above spi bus count");
	return NULL;
	}
	if (plat->adv_func->spi_init_pre != NULL) {
	if (plat->adv_func->spi_init_pre(bus) != MRAA_SUCCESS) {
	return NULL;
	}
	}

	if (!plat->no_bus_mux) {
	int pos = plat->spi_bus[bus].sclk;
	if (plat->pins[pos].spi.mux_total > 0) {
	if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
	syslog(LOG_ERR, "spi: failed to set-up spi sclk multiplexer");
	return NULL;
	}
	}

	pos = plat->spi_bus[bus].mosi;
	if (plat->pins[pos].spi.mux_total > 0) {
	if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
	syslog(LOG_ERR, "spi: failed to set-up spi mosi multiplexer");
	return NULL;
	}
	}

	pos = plat->spi_bus[bus].miso;
	if (plat->pins[pos].spi.mux_total > 0) {
	if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
	syslog(LOG_ERR, "spi: failed to set-up spi miso multiplexer");
	return NULL;
	}
	}

	pos = plat->spi_bus[bus].cs;
	if (plat->pins[pos].spi.mux_total > 0) {
	if (mraa_setup_mux_mapped(plat->pins[pos].spi) != MRAA_SUCCESS) {
	syslog(LOG_ERR, "spi: failed to set-up spi cs multiplexer");
	return NULL;
	}
	}
	}
	mraa_spi_context dev = mraa_spi_init_raw(plat->spi_bus[bus].bus_id, plat->spi_bus[bus].slave_s);

	if (plat->adv_func->spi_init_post != NULL) {
	mraa_result_t ret = plat->adv_func->spi_init_post(dev);
	if (ret != MRAA_SUCCESS) {
	free(dev);
	return NULL;
	}
	}

	return dev;
	}

	mraa_spi_context
	mraa_spi_init_raw(unsigned int bus, unsigned int cs)
	{
	mraa_spi_context dev = mraa_spi_init_internal(plat == NULL ? NULL : plat->adv_func);
	if (dev == NULL) {
	syslog(LOG_CRIT, "spi: Failed to allocate memory for context");
	return NULL;
	}

	char path[MAX_SIZE];
	sprintf(path, "/dev/spidev%u.%u", bus, cs);

	dev->devfd = open(path, O_RDWR);
	if (dev->devfd < 0) {
	syslog(LOG_ERR, "spi: Failed opening SPI Device. bus:%s", path);
	free(dev);
	return NULL;
	}

	int speed = 0;
	if (ioctl(dev->devfd, SPI_IOC_RD_MAX_SPEED_HZ, &speed) != -1) {
	dev->clock = speed;
	} else {
	// We had this on Galileo Gen1, so let it be a fallback value
	dev->clock = 4000000;
	syslog(LOG_WARNING, "spi: Max speed query failed, setting %d", dev->clock);
	}

	if (mraa_spi_mode(dev, MRAA_SPI_MODE0) != MRAA_SUCCESS) {
	free(dev);
	return NULL;
	}

	if (mraa_spi_lsbmode(dev, 0) != MRAA_SUCCESS) {
	free(dev);
	return NULL;
	}

	if (mraa_spi_bit_per_word(dev, 8) != MRAA_SUCCESS) {
	free(dev);
	return NULL;
	}

	return dev;
	}

	mraa_result_t
	mraa_spi_mode(mraa_spi_context dev, mraa_spi_mode_t mode)
	{
	uint8_t spi_mode = 0;
	switch (mode) {
	case MRAA_SPI_MODE0:
	spi_mode = SPI_MODE_0;
	break;
	case MRAA_SPI_MODE1:
	spi_mode = SPI_MODE_1;
	break;
	case MRAA_SPI_MODE2:
	spi_mode = SPI_MODE_2;
	break;
	case MRAA_SPI_MODE3:
	spi_mode = SPI_MODE_3;
	break;
	default:
	spi_mode = SPI_MODE_0;
	break;
	}

	if (ioctl(dev->devfd, SPI_IOC_WR_MODE, &spi_mode) < 0) {
	syslog(LOG_ERR, "spi: Failed to set spi mode");
	return MRAA_ERROR_INVALID_RESOURCE;
	}

	dev->mode = spi_mode;
	return MRAA_SUCCESS;
	}

	mraa_result_t
	mraa_spi_frequency(mraa_spi_context dev, int hz)
	{
	int speed = 0;
	dev->clock = hz;
	if (ioctl(dev->devfd, SPI_IOC_RD_MAX_SPEED_HZ, &speed) != -1) {
	if (speed < hz) {
	dev->clock = speed;
	syslog(LOG_WARNING, "spi: Selected speed reduced to max allowed speed");
	}
	}
	return MRAA_SUCCESS;
	}

	mraa_result_t
	mraa_spi_lsbmode(mraa_spi_context dev, mraa_boolean_t lsb)
	{
	if (IS_FUNC_DEFINED(dev, spi_lsbmode_replace)) {
	return dev->advance_func->spi_lsbmode_replace(dev, lsb);
	}

	uint8_t lsb_mode = (uint8_t) lsb;
	if (ioctl(dev->devfd, SPI_IOC_WR_LSB_FIRST, &lsb_mode) < 0) {
	syslog(LOG_ERR, "spi: Failed to set bit order");
	return MRAA_ERROR_INVALID_RESOURCE;
	}
	if (ioctl(dev->devfd, SPI_IOC_RD_LSB_FIRST, &lsb_mode) < 0) {
	syslog(LOG_ERR, "spi: Failed to set bit order");
	return MRAA_ERROR_INVALID_RESOURCE;
	}
	dev->lsb = lsb;
	return MRAA_SUCCESS;
	}

	mraa_result_t
	mraa_spi_bit_per_word(mraa_spi_context dev, unsigned int bits)
	{
	if (ioctl(dev->devfd, SPI_IOC_WR_BITS_PER_WORD, &bits) < 0) {
	syslog(LOG_ERR, "spi: Failed to set bit per word");
	return MRAA_ERROR_INVALID_RESOURCE;
	}
	dev->bpw = bits;
	return MRAA_SUCCESS;
	}

	int
	mraa_spi_write(mraa_spi_context dev, uint8_t data)
	{
	struct spi_ioc_transfer msg;
	memset(&msg, 0, sizeof(msg));

	uint16_t length = 1;

	unsigned long recv = 0;
	msg.tx_buf = (unsigned long) &data;
	msg.rx_buf = (unsigned long) &recv;
	msg.speed_hz = dev->clock;
	msg.bits_per_word = dev->bpw;
	msg.delay_usecs = 0;
	msg.len = length;
	if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
	syslog(LOG_ERR, "spi: Failed to perform dev transfer");
	return -1;
	}
	return (int) recv;
	}

	int
	mraa_spi_write_word(mraa_spi_context dev, uint16_t data)
	{
	struct spi_ioc_transfer msg;
	memset(&msg, 0, sizeof(msg));

	uint16_t length = 2;

	uint16_t recv = 0;
	msg.tx_buf = (unsigned long) &data;
	msg.rx_buf = (unsigned long) &recv;
	msg.speed_hz = dev->clock;
	msg.bits_per_word = dev->bpw;
	msg.delay_usecs = 0;
	msg.len = length;
	if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
	syslog(LOG_ERR, "spi: Failed to perform dev transfer");
	return -1;
	}
	return (int) recv;
	}

	mraa_result_t
	mraa_spi_transfer_buf(mraa_spi_context dev, uint8_t* data, uint8_t* rxbuf, int length)
	{
	struct spi_ioc_transfer msg;
	memset(&msg, 0, sizeof(msg));

	msg.tx_buf = (unsigned long) data;
	msg.rx_buf = (unsigned long) rxbuf;
	msg.speed_hz = dev->clock;
	msg.bits_per_word = dev->bpw;
	msg.delay_usecs = 0;
	msg.len = length;
	if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
	syslog(LOG_ERR, "spi: Failed to perform dev transfer");
	return MRAA_ERROR_INVALID_RESOURCE;
	}
	return MRAA_SUCCESS;
	}

	mraa_result_t
	mraa_spi_transfer_buf_word(mraa_spi_context dev, uint16_t* data, uint16_t* rxbuf, int length)
	{
	struct spi_ioc_transfer msg;
	memset(&msg, 0, sizeof(msg));

	msg.tx_buf = (unsigned long) data;
	msg.rx_buf = (unsigned long) rxbuf;
	msg.speed_hz = dev->clock;
	msg.bits_per_word = dev->bpw;
	msg.delay_usecs = 0;
	msg.len = length;
	if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
	syslog(LOG_ERR, "spi: Failed to perform dev transfer");
	return MRAA_ERROR_INVALID_RESOURCE;
	}
	return MRAA_SUCCESS;
	}

	uint8_t*
	mraa_spi_write_buf(mraa_spi_context dev, uint8_t* data, int length)
	{
	uint8_t* recv = malloc(sizeof(uint8_t) * length);

	if (mraa_spi_transfer_buf(dev, data, recv, length) != MRAA_SUCCESS) {
	free(recv);
	return NULL;
	}
	return recv;
	}

	uint16_t*
	mraa_spi_write_buf_word(mraa_spi_context dev, uint16_t* data, int length)
	{
	uint16_t* recv = malloc(sizeof(uint16_t) * length);

	if (mraa_spi_transfer_buf_word(dev, data, recv, length) != MRAA_SUCCESS) {
	free(recv);
	return NULL;
	}
	return recv;
	}

	mraa_result_t
	mraa_spi_stop(mraa_spi_context dev)
	{
	close(dev->devfd);
	free(dev);
	return MRAA_SUCCESS;
	}