mpm: Add prefs modules

- prefs is a module for centralized preferences management
- Uses Python's ConfigParser module

4 files changed, 99 insertions, 2 deletions

diff --git a/mpm/python/usrp_mpm/CMakeLists.txt b/mpm/python/usrp_mpm/CMakeLists.txt
index 6b2f1a5a0..a3585cc6b 100644
--- a/mpm/python/usrp_mpm/CMakeLists.txt
+++ b/mpm/python/usrp_mpm/CMakeLists.txt
@@ -20,6 +20,7 @@ SET(USRP_MPM_TOP_FILES
     ${CMAKE_CURRENT_SOURCE_DIR}/mpmlog.py
     ${CMAKE_CURRENT_SOURCE_DIR}/mpmtypes.py
     ${CMAKE_CURRENT_SOURCE_DIR}/mpmutils.py
+    ${CMAKE_CURRENT_SOURCE_DIR}/prefs.py
     ${CMAKE_CURRENT_SOURCE_DIR}/rpc_server.py
 )
 LIST(APPEND USRP_MPM_FILES ${USRP_MPM_TOP_FILES})
diff --git a/mpm/python/usrp_mpm/mpmlog.py b/mpm/python/usrp_mpm/mpmlog.py
index 0c37e92bf..113d4bd06 100644
--- a/mpm/python/usrp_mpm/mpmlog.py
+++ b/mpm/python/usrp_mpm/mpmlog.py
@@ -148,7 +148,7 @@ def get_main_logger(
         DEFAULT_LOG_LEVEL - log_default_delta * 10,
         CRITICAL
     ))
-    default_log_level = max(1, default_log_level - (default_log_level % 10))
+    default_log_level = max(TRACE, default_log_level - (default_log_level % 10))
     LOGGER.setLevel(default_log_level)
     # Connect to C++ logging:
     if LOGGER.cpp_log_buf is not None:
@@ -160,6 +160,10 @@ def get_main_logger(
                 lib_logger.log(log_level, "[%s] %s",
                                component, message.strip())
         LOGGER.cpp_log_buf.set_notify_callback(log_from_cpp)
+    # Flush errors stuck in the prefs module:
+    log = LOGGER.getChild('prefs')
+    for err_key, err_msg in mpm_prefs['__ERRORS__'].items():
+        log.error('%s: %s', err_key, err_msg)
     return LOGGER
 
 def get_logger(child_name):
diff --git a/mpm/python/usrp_mpm/prefs.py b/mpm/python/usrp_mpm/prefs.py
new file mode 100644
index 000000000..d244a0b42
--- /dev/null
+++ b/mpm/python/usrp_mpm/prefs.py
@@ -0,0 +1,92 @@
+#
+# Copyright 2018 Ettus Research, a National Instruments Company
+#
+# SPDX-License-Identifier: GPL-3.0
+#
+"""
+MPM preferences management
+"""
+
+import configparser
+from builtins import object
+from usrp_mpm.mpmlog import TRACE, DEBUG, INFO, WARNING, ERROR, CRITICAL
+
+# Store the global preferences object
+_PREFS = None
+
+### MPM defaults ##############################################################
+MPM_DEFAULT_CONFFILE_PATH = '/etc/uhd/mpm.conf'
+MPM_DEFAULT_LOG_LEVEL = 'info'
+MPM_DEFAULT_LOG_BUF_SIZE = 100 # Number of log records to buf
+
+class _MPMPrefs(configparser.ConfigParser):
+    """
+    Container for MPM preferences.
+
+    On initialization, it will read preferences from the system-wide config
+    file, if available, and from environment variables.
+    Settings can be updated at any time (e.g., because want to factor in
+    command line arguments).
+
+    This class also encodes default prefs in the self.default_prefs dictionary.
+    Said dictionary needs to be compatible with the ConfigParser.read_dict()
+    API call (refer to the Python documentation).
+    """
+    default_prefs = {
+        'mpm': {
+            'log_level': MPM_DEFAULT_LOG_LEVEL,
+            'log_buf_size': MPM_DEFAULT_LOG_BUF_SIZE,
+        },
+    }
+
+    def __init__(self):
+        configparser.ConfigParser.__init__(self)
+        self.read_dict(self.default_prefs)
+        self._errors = []
+        try:
+            self.read(MPM_DEFAULT_CONFFILE_PATH)
+        except configparser.Error as ex:
+            self._errors.append('Config file parsing error: {}'.format(str(ex)))
+
+    def get_log_level(self):
+        """
+        Return the selected default log level as an integer, usable by the
+        logging API. This is a safe call, it will always return a useful value.
+        Because this gets called as part of the logging API, it can't log any
+        error messages. It will store them in the object itself under the
+        __ERRORS__ section, key 'log_level'.
+        """
+        log_level = self.get('mpm', 'log_level').lower()
+        log_level_map = {
+            'trace': TRACE,
+            'debug': DEBUG,
+            'info': INFO,
+            'warning': WARNING,
+            'error': ERROR,
+            'critical': CRITICAL,
+        }
+        if log_level not in log_level_map:
+            self._errors.append('Invalid log level: {}'.format(log_level))
+            # Note: After this function returns, we can use the logger so we
+            # don't need to use this awkward side channel anymore!
+        return log_level_map.get(
+            log_level,
+            log_level_map[MPM_DEFAULT_LOG_LEVEL]
+        )
+
+    def get_log_errors(self):
+        """
+        Returns errors that were generated during init but couldn't be logged
+        because the logger isn't ready yet.
+        """
+        return self._errors
+
+def get_prefs():
+    """
+    Return singleton preferences object. It's an object of type ConfigParser.
+    """
+    global _PREFS
+    if _PREFS is None:
+        _PREFS = _MPMPrefs()
+    return _PREFS
+
diff --git a/mpm/python/usrp_mpm/sys_utils/CMakeLists.txt b/mpm/python/usrp_mpm/sys_utils/CMakeLists.txt
index 5a9d79034..ee7c249df 100644
--- a/mpm/python/usrp_mpm/sys_utils/CMakeLists.txt
+++ b/mpm/python/usrp_mpm/sys_utils/CMakeLists.txt
@@ -1,5 +1,5 @@
 #
-# Copyright 2017 Ettus Research, National Instruments Company
+# Copyright 2017 Ettus Research, a National Instruments Company
 #
 # SPDX-License-Identifier: GPL-3.0
 #