mpm: add helper for symbol lookup

Add a helper that can lookup a device via a device tree symbol.

Co-authored-by: Lars Amsel <lars.amsel@ni.com>
Co-authored-by: Michael Auchter <michael.auchter@ni.com>

1 files changed, 81 insertions, 0 deletions

diff --git a/mpm/python/usrp_mpm/sys_utils/udev.py b/mpm/python/usrp_mpm/sys_utils/udev.py
index 70b3bcb65..ef79ed747 100644
--- a/mpm/python/usrp_mpm/sys_utils/udev.py
+++ b/mpm/python/usrp_mpm/sys_utils/udev.py
@@ -8,7 +8,65 @@ 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):
     """
@@ -41,3 +99,26 @@ def get_spidev_nodes(spi_master):
         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'])