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#
# Copyright 2017 Ettus Research (National Instruments)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
"""
Access to UIO mapped memory.
"""
import struct
import os
import mmap
class uio(object):
"""
Provides peek/poke interfaces for uio-mapped memory.
Arguments:
path -- Path to UIO device, e.g. '/dev/uio0'
length -- Number of bytes in the address space (is passed to mmap.mmap).
Must be at least one page size
read_only -- Boolean, True == ro, False == rw
offset -- Passed to mmap.mmap
"""
def __init__(self, path, length, read_only=True, offset=None):
# Python can't tell the size of a uio device
assert length >= mmap.PAGESIZE
offset = offset or 0
self._path = path
self._read_only = read_only
self._fd = os.open(path, os.O_RDONLY if read_only else os.O_RDWR)
self._mm = mmap.mmap(
self._fd,
length,
flags=mmap.MAP_SHARED,
prot=mmap.PROT_READ | (0 if read_only else mmap.PROT_WRITE),
offset=offset,
)
def peek32(self, addr):
"""
Returns the 32-bit value starting at address addr as an integer
"""
return struct.unpack('@I', self._mm[addr:addr+4])[0]
def poke32(self, addr, val):
"""
Writes the 32-bit value val to address starting at addr.
Will throw if read_only was set to True.
A value that exceeds 32 bits will be truncated to 32 bits.
"""
assert not self._read_only
self._mm[addr:addr+4] = struct.pack(
'@I',
(val & 0xFFFFFFFF),
)
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