'''
Stripped down version from https://github.com/vsergeev/python-periphery/blob/master/periphery/mmio.py
'''
import mmap
import os
import struct
import sys
# Alias long to int on Python 3
if sys.version_info[0] >= 3:
long = int
class MMIOError(IOError):
"""Base class for MMIO errors."""
pass
class MMIO(object):
def __init__(self, physaddr, size):
"""Instantiate an MMIO object and map the region of physical memory
specified by the address base `physaddr` and size `size` in bytes.
Args:
physaddr (int, long): base physical address of memory region.
size (int, long): size of memory region.
Returns:
MMIO: MMIO object.
Raises:
MMIOError: if an I/O or OS error occurs.
TypeError: if `physaddr` or `size` types are invalid.
"""
self.mapping = None
self._open(physaddr, size)
def __del__(self):
self.close()
def __enter__(self):
pass
def __exit__(self, t, value, traceback):
self.close()
def _open(self, physaddr, size):
if not isinstance(physaddr, (int, long)):
raise TypeError("Invalid physaddr type, should be integer.")
if not isinstance(size, (int, long)):
raise TypeError("Invalid size type, should be integer.")
pagesize = os.sysconf(os.sysconf_names['SC_PAGESIZE'])
self._physaddr = physaddr
self._size = size
self._aligned_physaddr = physaddr - (physaddr % pagesize)
self._aligned_size = size + (physaddr - self._aligned_physaddr)
try:
fd = os.open("/dev/mem", os.O_RDWR | os.O_SYNC)
except OSError as e:
raise MMIOError(e.errno, "Opening /dev/mem: " + e.strerror)
try:
self.mapping = mmap.mmap(
fd, self._aligned_size, flags=mmap.MAP_SHARED, prot=mmap.PROT_WRITE, offset=self._aligned_physaddr)
except OSError as e:
raise MMIOError(e.errno, "Mapping /dev/mem: " + e.strerror)
try:
os.close(fd)
except OSError as e:
raise MMIOError(e.errno, "Closing /dev/mem: " + e.strerror)
# Methods
def _adjust_offset(self, offset):
return offset + (self._physaddr - self._aligned_physaddr)
def _validate_offset(self, offset, length):
if (offset + length) > self._aligned_size:
raise ValueError("Offset out of bounds.")
def read32(self, offset):
"""Read 32-bits from the specified `offset` in bytes, relative to the
base physical address of the MMIO region.
Args:
offset (int, long): offset from base physical address, in bytes.
Returns:
int: 32-bit value read.
Raises:
TypeError: if `offset` type is invalid.
ValueError: if `offset` is out of bounds.
"""
if not isinstance(offset, (int, long)):
raise TypeError("Invalid offset type, should be integer.")
offset = self._adjust_offset(offset)
self._validate_offset(offset, 4)
return struct.unpack("=L", self.mapping[offset:offset + 4])[0]
def write32(self, offset, value):
"""Write 32-bits to the specified `offset` in bytes, relative to the
base physical address of the MMIO region.
Args:
offset (int, long): offset from base physical address, in bytes.
value (int, long): 32-bit value to write.
Raises:
TypeError: if `offset` or `value` type are invalid.
ValueError: if `offset` or `value` are out of bounds.
"""
if not isinstance(offset, (int, long)):
raise TypeError("Invalid offset type, should be integer.")
if not isinstance(value, (int, long)):
raise TypeError("Invalid value type, should be integer.")
if value < 0 or value > 0xffffffff:
raise ValueError("Value out of bounds.")
offset = self._adjust_offset(offset)
self._validate_offset(offset, 4)
self.mapping[offset:offset + 4] = struct.pack("=L", value)
def close(self):
"""Unmap the MMIO object's mapped physical memory."""
if self.mapping is None:
return
self.mapping.close()
self.mapping = None
self._fd = None
# String representation
def __str__(self):
return "MMIO 0x%08x (size=%d)" % (self.base, self.size)
