// This is NEW CODE, a VM ram/disk access driver for use in the VM
// This driver is intended to be very simple to read/write blocks.
#include "types.h"
#include "param.h"
#include "riscv.h"
#include "defs.h"
#include "vmrd.h"

sched_spinlock_t vmrd_lock;

// This doesn't really belong here but is used to enable/disable debug
// tracing in the VM.
void vmrd_settracing(int onoroff) {
  if (onoroff) {
    vmrd_action = 't';
  } else {
    vmrd_action = 'e';
  }
  return;
}

// Returns a major version number >= 1 if the virtual ram/disk device is
// present and 0 otherwise.
int vmrd_present() {
  if (vmrd_magic == VMRD_MAGIC) {
    return 1; // Only 1 version exists for now
  } else {
    return 0;
  }
}
  

// Initialises vmrd, returning a non-zero value on failure (e.g. if not present)
int vmrd_init() {
  if (!vmrd_present()) {
    return -1;
  }
  
  initlock(&vmrd_lock, "VMRD");
  
  return 0;
}

// Performs a read/write of a block.
int vmrd_rw(diskio_buffer_t* buffer, int writing) {
  acquire(&vmrd_lock);
  
  vmrd_blksize = (unsigned int) buffer->owner->blocksize;
  vmrd_memaddr = (unsigned long) buffer->data;
  vmrd_blkaddr = buffer->blocknumber;
  vmrd_action = writing ? 'w' : 'r';
  
  while (vmrd_action != 's') {
    if (vmrd_action == 'f') {
      
      release(&vmrd_lock);
      
      return -1;
    }
  }
  
  release(&vmrd_lock);
  
  return 0;
}