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