SPI Raspberry Pi host not supported on 64bit platforms

[humphrey-xmos]

SPI is currently supported via libbcm2835.a this is for 32bit hosts and certainly Buster OS.

For 64bit OS and possibly post-Buster, there is spidev access. After enabling SPI interface in raspi-config.

Determine which OS spidev becamse availabe in, update CMake.

Overhaul lib_device_control SPI layer, with something like:

/*
 * spi-driver-speed.c
 * 2016-11-23
 * Public Domain
*/

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

/*
spi-driver-speed.c

gcc -o spi-driver-speed spi-driver-speed.c

./spi-driver-speed [bytes [bps [loops] ] ]
*/

#define LOOPS 10000
#define SPEED 1000000
#define BYTES 3

double time_time(void)
{
   struct timeval tv;
   double t;

   gettimeofday(&tv, 0);

   t = (double)tv.tv_sec + ((double)tv.tv_usec / 1E6);

   return t;
}

int spiOpen(unsigned spiChan, unsigned spiBaud, unsigned spiFlags)
{
   int i,fd;
   char  spiMode;
   char  spiBits  = 8;
   char dev[32];

   spiMode  = spiFlags & 3;
   spiBits  = 8;

   sprintf(dev, "/dev/spidev0.%d", spiChan);

   if ((fd = open(dev, O_RDWR)) < 0)
   {
      return -1;
   }

   if (ioctl(fd, SPI_IOC_WR_MODE, &spiMode) < 0)
   {
      close(fd);
      return -2;
   }

   if (ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &spiBits) < 0)
   {
      close(fd);
      return -3;
   }

   if (ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &spiBaud) < 0)
   {
      close(fd);
      return -4;
   }

   return fd;
}

int spiClose(int fd)
{
   return close(fd);
}

int spiRead(int fd, unsigned speed, char *buf, unsigned count)
{
   int err;
   struct spi_ioc_transfer spi;

   memset(&spi, 0, sizeof(spi));

   spi.tx_buf        = (unsigned) NULL;
   spi.rx_buf        = (unsigned) buf;
   spi.len           = count;
   spi.speed_hz      = speed;
   spi.delay_usecs   = 0;
   spi.bits_per_word = 8;
   spi.cs_change     = 0;

   err = ioctl(fd, SPI_IOC_MESSAGE(1), &spi);

   return err;
}

int spiWrite(int fd, unsigned speed, char *buf, unsigned count)
{
   int err;
   struct spi_ioc_transfer spi;

   memset(&spi, 0, sizeof(spi));

   spi.tx_buf        = (unsigned) buf;
   spi.rx_buf        = (unsigned) NULL;
   spi.len           = count;
   spi.speed_hz      = speed;
   spi.delay_usecs   = 0;
   spi.bits_per_word = 8;
   spi.cs_change     = 0;

   err = ioctl(fd, SPI_IOC_MESSAGE(1), &spi);

   return err;
}

int spiXfer(int fd, unsigned speed, char *txBuf, char *rxBuf, unsigned count)
{
   int err;
   struct spi_ioc_transfer spi;

   memset(&spi, 0, sizeof(spi));

   spi.tx_buf        = (unsigned long)txBuf;
   spi.rx_buf        = (unsigned long)rxBuf;
   spi.len           = count;
   spi.speed_hz      = speed;
   spi.delay_usecs   = 0;
   spi.bits_per_word = 8;
   spi.cs_change     = 0;

   err = ioctl(fd, SPI_IOC_MESSAGE(1), &spi);

   return err;
}

#define MAX_SPI_BUFSIZ 8192

char RXBuf[MAX_SPI_BUFSIZ];
char TXBuf[MAX_SPI_BUFSIZ];

int bytes = BYTES;
int speed = SPEED;
int loops = LOOPS;

int main(int argc, char * argv[])
{
   int i, fd;
   double start, diff, sps;

   if (argc > 1) bytes = atoi(argv[1]);
   else printf("./spi-driver-speed [bytes [bps [loops] ] ]\n\n");

   if ((bytes < 1) || (bytes > MAX_SPI_BUFSIZ)) bytes = BYTES;

   if (argc > 2) speed = atoi(argv[2]);
   if ((speed < 32000) || (speed > 250000000)) speed = SPEED;

   if (argc > 3) loops = atoi(argv[3]);
   if ((loops < 1) || (loops > 10000000)) loops = LOOPS;

   fd = spiOpen(0, speed, 0);

   start = time_time();

   if (fd < 0) return 1;

   for (i=0; i<loops; i++)
   {
      spiXfer(fd, speed, TXBuf, RXBuf, bytes);
   }

   diff = time_time() - start;

   close(fd);

   printf("sps=%.1f: %d bytes @ %d bps (loops=%d time=%.1f)\n",
      (double)loops / diff, bytes, speed, loops, diff);
}