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#
# Copyright 2017 Ettus Research, a National Instruments Company
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
"""
Utilities for udev lookups
"""
import os
import glob
import pyudev
from pathlib import Path
DT_BASE = "/proc/device-tree"
def get_eeprom_paths_by_symbol(symbol_name_glob):
"""
Searches for EEPROM file locaction of symbol names under
/proc/device-tree/__symbols__.
args: symbol_name_glob: symbol name(s) to search (allows glob expressions)
returns: dictionary with name found under __symbols__ as key
and corresponding nvmem file path as value.
The dictionary keys are sorted alphabetically.
raises: FileNotFoundExcepiton: in case a symbol file could not be read.
"""
symbol_base = os.path.join(DT_BASE, "__symbols__")
context = pyudev.Context()
devices = context.list_devices(subsystem="nvmem")
of_nodes = [os.path.join(dev.sys_path, "of_node") for dev in devices]
def read_symbol_file(symbol_file):
with open(symbol_file) as f:
symbol_path = f.read()
# remove leading slash and trailing terminating char before
# building the full path for symbol
symbol_path = os.path.join(DT_BASE, symbol_path[1:-1])
return symbol_path
def find_device_path(path):
for dev in of_nodes:
if not os.path.exists(dev):
# not all nvmem devices have an of_node
continue
elif os.path.samefile(dev, path):
return os.path.join(os.path.dirname(dev), "nvmem")
return None
eeproms = glob.glob(os.path.join(symbol_base, symbol_name_glob))
paths = {os.path.basename(eeprom): read_symbol_file(eeprom)
for eeprom in eeproms}
return {name: find_device_path(path)
for name, path in sorted(paths.items())}
def get_device_from_dt_symbol(symbol, subsystem=None, context=None):
"""
Return the device associated with the device tree symbol, which usually
is a label on a specific node of interest
"""
symfile = Path(DT_BASE) / '__symbols__' / symbol
fullname = symfile.read_text()
if context is None:
context = pyudev.Context()
devices = list(context.list_devices(OF_FULLNAME=fullname, subsystem=subsystem))
if not devices:
return None
return devices[0]
def get_eeprom_paths(address):
"""
Return list of EEPROM device paths for a given I2C address.
If no device paths are found, an empty list is returned.
"""
context = pyudev.Context()
parent = pyudev.Device.from_name(context, "platform", address)
paths = [d.device_node if d.device_node is not None else d.sys_path
for d in context.list_devices(parent=parent, subsystem="nvmem")]
if len(paths) == 0:
return []
# We need to sort this so 9-0050 comes before 10-0050 (etc.)
maxlen = max((len(os.path.split(p)[1]) for p in paths))
paths = sorted(
paths,
key=lambda x: "{:>0{maxlen}}".format(os.path.split(x)[1], maxlen=maxlen)
)
return [os.path.join(x, 'nvmem') for x in paths]
def get_spidev_nodes(spi_master):
"""
Return list of spidev device paths for a given SPI master. If no valid paths
can be found, an empty list is returned.
"""
context = pyudev.Context()
parent = pyudev.Device.from_name(context, "platform", spi_master)
return [
device.device_node
for device in context.list_devices(parent=parent, subsystem="spidev")
]
def get_device_from_symbol(symbol, subsystems):
"""
Find the first device and return its name where the parent device the DT
symbol name matches and the hierarchy of subsystems (e.g. ['spi', 'spidev'])
match
"""
assert isinstance(subsystems,list)
context = pyudev.Context()
device = get_device_from_dt_symbol(symbol, subsystem=subsystems.pop(0), context=context)
if device is None:
return None
for subsystem in subsystems:
devices = list(context.list_devices(parent=device, subsystem=subsystem))
if not devices:
return None
device = devices[0]
return device.properties.get('DEVNAME')
def dt_symbol_get_spidev(symbol):
"""
Return spidev associated with the given device tree symbol
"""
return get_device_from_symbol(symbol, ['spi', 'spidev'])
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