uhd/mpm/python/usrp_mpm/uio.py

#
# 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
import pyudev
from .mpmlog import get_logger

UIO_SYSFS_BASE_DIR = '/sys/class/uio'
UIO_DEV_BASE_DIR = '/dev'

def get_all_uio_devs():
    """
    Return a list of all uio devices. Will look something like
    ['uio0', 'uio1', ...].
    """
    try:
        context = pyudev.Context()
        paths = [os.path.split(device.device_node)[-1]
                 for device in context.list_devices(subsystem="uio")]
        return paths
    except OSError:
        # Typically means UIO devices
        return []

def get_uio_map_info(uio_dev, map_num):
    """
    Returns all the map info for a given UIO device and map number.
    Example: If uio_dev is 'uio0', and map_num is 0, it will list all files
    in /sys/class/uio/uio0/maps/map0/ and create a dictionary with filenames
    as keys and content as value.

    Numbers are casted to numbers automatically. Strings remain strings.
    """
    map_info = {}
    map_info_path = os.path.join(
        UIO_SYSFS_BASE_DIR, uio_dev, 'maps', 'map{0}'.format(map_num)
    )
    for info_file in os.listdir(map_info_path):
        map_info_value = open(os.path.join(map_info_path, info_file), 'r').read().strip()
        try:
            map_info[info_file] = int(map_info_value, 0)
        except ValueError:
            map_info[info_file] = map_info_value
    return map_info

def find_uio_device(label, logger=None):
    """
    Given a label, returns a tuple (uio_device, map_info).
    uio_device is something like '/dev/uio0'. map_info is a dictionary with
    information regarding the UIO device read from the map info sysfs dir.
    Note: We assume a single map (map0) for all UIO devices here.
    """
    uio_devices = get_all_uio_devs()
    if logger:
        logger.trace("Found the following UIO devices: `{0}'".format(','.join(uio_devices)))
    for uio_device in uio_devices:
        map0_info = get_uio_map_info(uio_device, 0)
        logger.trace("{0} has map info: {1}".format(uio_device, map0_info))
        if map0_info.get('name') == label:
            if logger:
                logger.trace("Device matches label: `{0}'".format(uio_device))
            return os.path.join(UIO_DEV_BASE_DIR, uio_device), map0_info
    if logger:
        logger.warning("Found no matching UIO device for label `{0}'".format(label))
    return None, None

class UIO(object):
    """
    Provides peek/poke interfaces for uio-mapped memory.

    Arguments:
    label -- Label of the UIO device. The label is set in the device tree
             overlay
    path -- Path to UIO device, e.g. '/dev/uio0'. This is ignored if 'label' is
            provided.
    length -- Number of bytes in the address space (is passed to mmap.mmap).
              This is usually automatically determined. No need to set it.
              Unless you really know what you're doing.
    read_only -- Boolean; True == ro, False == rw
    offset -- Passed to mmap.mmap.
              This is usually automatically determined. No need to set it.
              Unless you really know what you're doing.
    """
    def __init__(self, label=None, path=None, length=None, read_only=True, offset=None):
        self.log = get_logger('UIO')
        if label is None:
            self._path = path
            self.log.trace("Using UIO device `{0}'".format(path))
            uio_device = os.path.split(path)[-1]
            self.log.trace("Getting map info for UIO device `{0}'".format(uio_device))
            map_info = get_uio_map_info(uio_device, 0)
            # Python can't tell the size of a uio device by itself
            assert length is not None
        else:
            self.log.trace("Using UIO device by label `{0}'".format(label))
            self._path, map_info = find_uio_device(label, self.log)
        offset = offset or map_info['offset'] # If we ever support multiple maps, check if this is correct...
        assert offset == 0 # ...and then remove this line
        length = length or map_info['size']
        self.log.trace("UIO device is being opened read-{0}.".format("only" if read_only else "write"))
        if self._path is None:
            self.log.error("Could not find a UIO device for label {0}".format(label))
            raise RuntimeError("Could not find a UIO device for label {0}".format(label))
        self._read_only = read_only
        self.log.trace("Opening UIO device file {}...".format(self._path))
        self._fd = os.open(self._path, os.O_RDONLY if read_only else os.O_RDWR)
        self.log.trace("Calling mmap({fd}, length={length}, offset={offset})".format(
            fd=self._fd, length=hex(length), offset=hex(offset)
        ))
        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),
        )