libmetal R5 receiver

#include <metal/sys.h>
#include <metal/device.h>
#include <metal/io.h>
#include <metal/alloc.h>

#define BUS_NAME        "generic"
#define SHM_DEV_NAME    "3e800000.shm"

#define SHM_BASE_ADDR   0x3E800000
/* Each I/O region can contain multiple pages.
 * In baremetal system, the memory mapping is flat, there is no
 * virtual memory.
 * We can assume there is only one page in the whole baremetal system.
 */
#define DEFAULT_PAGE_SHIFT (-1UL)
#define DEFAULT_PAGE_MASK  (-1UL)

// This stuff will eventually live in its own header
typedef struct {
  uint8_t status;
  uint8_t value;
} msgblock;

const int MSGBUF_LEN = 10;

const int LED_GPIO_BASE = 0x80000000;

int main(int argc, char* argv[])
{
  uint32_t* leds = (uint32_t*)LED_GPIO_BASE;
  *leds = 0x55;

  struct metal_init_params metal_param = METAL_INIT_DEFAULTS;
  metal_init(&metal_param);

  // Shared memory device
  struct metal_device dev = {
    .name = SHM_DEV_NAME,
    .bus = NULL,
    .num_regions = 1,
    .regions = {
      {
        .virt = (void *)SHM_BASE_ADDR,
        .physmap = (metal_phys_addr_t*)SHM_BASE_ADDR,
        .size = 0x800000,
        .page_shift = DEFAULT_PAGE_SHIFT,
        .page_mask = DEFAULT_PAGE_MASK,
        .mem_flags = NORM_SHARED_NCACHE |
            PRIV_RW_USER_RW,
        .ops = {NULL},
      }
    },
    .node = {NULL},
    .irq_num = 0,
    .irq_info = NULL,
  };


  // This isn't needed in the new version
  metal_bus_register(&metal_generic_bus);

  int err = metal_register_generic_device(&dev);
  if(err){
      print("Failed to register device\n");
  }

  struct metal_device* shm_dev;
  err = metal_device_open(BUS_NAME, SHM_DEV_NAME, &shm_dev);
  if(err){
      print("Failed to open device\n");
  }

  // Now get the I/O region
  struct metal_io_region *io = NULL;
  io = metal_device_io_region(shm_dev, 0);
  if(!io){
    print("Failed to get I/O region\n");
  }

  int msgcount = 0;

  union {
      msgblock msg;
      uint16_t raw;
  } message;

  while(1){
    Xil_DCacheInvalidateRange((uint32_t)SHM_BASE_ADDR, 0x100);

    // Get a message from the queue
    message.raw = metal_io_read16(io, msgcount*sizeof(msgblock));

    // If the message is valid, set the LEDs accordingly
    // Otherwise, just keep spinning
    if(message.msg.status == 0x01){
      *leds = message.msg.value;
      metal_io_write16(io, msgcount*sizeof(msgblock), 0); // Clear this message
      msgcount = (msgcount + 1) % MSGBUF_LEN;
    }
    sleep(1);
  }

  metal_device_close(shm_dev);
  metal_finish();
}