* writing the complete buffer in one function is much faster,
* then calling it for every bit
*/
-int altera_write_fn(void *buf, size_t len, int flush, int cookie)
+int altera_write_fn(const void *buf, size_t len, int flush, int cookie)
{
size_t bytecount = 0;
gpio_t *gpiop = (gpio_t *)MMAP_GPIO;