int SPI_transfer(int spidev_fd, void *tx_buffer, void *rx_buffer, int n_words) {
uint8_t bits_per_word;
uint32_t n_bytes;
struct spi_ioc_transfer transfer;
bits_per_word = SPI_getBitsPerWord(spidev_fd);
if (bits_per_word < 0) return bits_per_word;
n_bytes = (uint32_t) (((float) (bits_per_word * n_words)) / 8.0 + 0.5);
if (!n_bytes) return 0;
if (n_bytes > MAX_TRANSFER_SIZE) n_bytes = MAX_TRANSFER_SIZE;
transfer.tx_buf = (uint64_t*) tx_buffer;
transfer.rx_buf = (uint64_t*) rx_buffer;
transfer.len = n_bytes;
transfer.speed_hz = 0;
transfer.delay_usecs = 0;
transfer.bits_per_word = bits_per_word;
transfer.cs_change = 0;
if (ioctl(spidev_fd, SPI_IOC_MESSAGE(1), &transfer) < 0) return -1;
return (n_bytes<<3) / bits_per_word;
}
static PyObject *SPIDev_open(SPIDev *self, PyObject *args, PyObject *kwds) {
self->spidev_fd[0] = SPI_open(self->bus, 0);
if (self->spidev_fd[0] < 0) {
PyErr_SetString(PyExc_IOError, "could not open spidev");
return NULL;
}
self->bits_per_word = SPI_getBitsPerWord(self->spidev_fd[0]);
if (self->bits_per_word <= 8) {
self->bytes_per_word = 1;
}
else if (self->bits_per_word <= 16) {
self->bytes_per_word = 2;
}
else if (self->bits_per_word <= 32) {
self->bytes_per_word = 4;
}
if (self->mode_3wire) {
SPI_enable3Wire(self->spidev_fd[0]);
}
Py_INCREF(Py_None);
return Py_None;
}
