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// Communicating with an SPI device via linux spidev
//
// Copyright (C) 2017 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <fcntl.h> // open
#include <stdio.h> // snprintf
#include <unistd.h> // write
#include "command.h" // DECL_COMMAND
#include "internal.h" // report_errno
#include "sched.h" // shutdown
struct spi_s {
uint32_t bus, dev;
int fd;
};
static struct spi_s devices[16];
static int devices_count;
static int
spi_open(uint32_t bus, uint32_t dev)
{
// Find existing device (if already opened)
int i;
for (i=0; i<devices_count; i++)
if (devices[i].bus == bus && devices[i].dev == dev)
return devices[i].fd;
// Setup new SPI device
if (devices_count >= ARRAY_SIZE(devices))
shutdown("Too many spi devices");
char fname[256];
snprintf(fname, sizeof(fname), "/dev/spidev%d.%d", bus, dev);
int fd = open(fname, O_RDWR|O_CLOEXEC);
if (fd < 0) {
report_errno("open spi", fd);
shutdown("Unable to open spi device");
}
int ret = set_non_blocking(fd);
if (ret < 0)
shutdown("Unable to set non-blocking on spi device");
devices[devices_count].bus = bus;
devices[devices_count].dev = dev;
devices[devices_count].fd = fd;
return fd;
}
static void
spi_write(int fd, char *data, int len)
{
int ret = write(fd, data, len);
if (ret < 0) {
report_errno("write spi", ret);
shutdown("Unable to write to spi");
}
}
void
command_send_spi(uint32_t *args)
{
int fd = spi_open(args[0], args[1]);
uint8_t len = args[2];
char *msg = (void*)(size_t)args[3];
spi_write(fd, msg, len);
}
DECL_COMMAND(command_send_spi, "send_spi bus=%u dev=%u msg=%*s");
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