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+What: /sys/firmware/opal/elog
+Date: Feb 2014
+Contact: Stewart Smith <stewart@linux.vnet.ibm.com>
+Description:
+ This directory exposes error log entries retrieved
+ through the OPAL firmware interface.
+
+ Each error log is identified by a unique ID and will
+ exist until explicitly acknowledged to firmware.
+
+ Each log entry has a directory in /sys/firmware/opal/elog.
+
+ Log entries may be purged by the service processor
+ before retrieved by firmware or retrieved/acknowledged by
+ Linux if there is no room for more log entries.
+
+ In the event that Linux has retrieved the log entries
+ but not explicitly acknowledged them to firmware and
+ the service processor needs more room for log entries,
+ the only remaining copy of a log message may be in
+ Linux.
+
+ Typically, a user space daemon will monitor for new
+ entries, read them out and acknowledge them.
+
+ The service processor may be able to store more log
+ entries than firmware can, so after you acknowledge
+ an event from Linux you may instantly get another one
+ from the queue that was generated some time in the past.
+
+ The raw log format is a binary format. We currently
+ do not parse this at all in kernel, leaving it up to
+ user space to solve the problem. In future, we may
+ do more parsing in kernel and add more files to make
+ it easier for simple user space processes to extract
+ more information.
+
+ For each log entry (directory), there are the following
+ files:
+
+ ============== ================================================
+ id: An ASCII representation of the ID of the
+ error log, in hex - e.g. "0x01".
+
+ type: An ASCII representation of the type id and
+ description of the type of error log.
+ Currently just "0x00 PEL" - platform error log.
+ In the future there may be additional types.
+
+ raw: A read-only binary file that can be read
+ to get the raw log entry. These are
+ <16kb, often just hundreds of bytes and
+ "average" 2kb.
+
+ acknowledge: Writing 'ack' to this file will acknowledge
+ the error log to firmware (and in turn
+ the service processor, if applicable).
+ Shortly after acknowledging it, the log
+ entry will be removed from sysfs.
+ Reading this file will list the supported
+ operations (currently just acknowledge).
+ ============== ================================================