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Remove Non-Volatile Memory Driver chapter
There exists no standard Non-Volatile Memory Driver in the RTEMS code base. Close #2851.
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Sebastian Huber
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@ -53,7 +53,6 @@ to the Community Project hosted at http://www.rtems.org.
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real_time_clock
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ata
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ide_controller
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non_volatile_memory
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networking
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shared_memory_support
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frame_buffer
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@ -1,217 +0,0 @@
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.. comment SPDX-License-Identifier: CC-BY-SA-4.0
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.. COMMENT: Written by Eric Norum
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.. COMMENT: COPYRIGHT (c) 1988-2002.
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.. COMMENT: On-Line Applications Research Corporation (OAR).
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.. COMMENT: All rights reserved.
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Non-Volatile Memory Driver
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**************************
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The Non-Volatile driver is responsible for providing an interface to various
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types of non-volatile memory. These types of memory include, but are not
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limited to, Flash, EEPROM, and battery backed RAM. The capabilities provided
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by this class of device driver are:
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- Initialize the Non-Volatile Memory Driver
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- Optional Disable Read and Write Handlers
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- Open a Particular Memory Partition
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- Close a Particular Memory Partition
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- Read from a Particular Memory Partition
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- Write to a Particular Memory Partition
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- Erase the Non-Volatile Memory Area
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There is currently only one non-volatile device driver included in the RTEMS
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source tree. The information provided in this chapter is based on drivers
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developed for applications using RTEMS. It is hoped that this driver model
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information can form the basis for a standard non-volatile memory driver model
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that can be supported in future RTEMS distribution.
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Major and Minor Numbers
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=======================
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The ``major`` number of a device driver is its index in the RTEMS Device
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Address Table.
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A ``minor`` number is associated with each device instance managed by a
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particular device driver. An RTEMS minor number is an ``unsigned32`` entity.
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Convention calls dividing the bits in the minor number down into categories
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that specify an area of non-volatile memory and a partition with that area.
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This results in categories like the following:
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- ``area`` - indicates a block of non-volatile memory
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- ``partition`` - indicates a particular address range with an area
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From the above, it should be clear that a single device driver can support
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multiple types of non-volatile memory in a single system. The minor number is
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used to distinguish the types of memory and blocks of memory used for different
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purposes.
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Non-Volatile Memory Driver Configuration
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========================================
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There is not a standard non-volatile driver configuration table but some fields
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are common across different drivers. The non-volatile memory driver
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configuration table is typically an array of structures with each structure
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containing the information for a particular area of non-volatile memory. The
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following is a list of the type of information normally required to configure
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each area of non-volatile memory.
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``memory_type``
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is the type of memory device in this area. Choices are battery backed RAM,
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EEPROM, Flash, or an optional user-supplied type. If the user-supplied
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type is configured, then the user is responsible for providing a set of
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routines to program the memory.
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``memory``
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is the base address of this memory area.
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``attributes``
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is a pointer to a memory type specific attribute block. Some of the fields
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commonly contained in this memory type specific attribute structure area:
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``use_protection_algorithm``
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is set to TRUE to indicate that the protection (i.e. locking) algorithm
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should be used for this area of non-volatile memory. A particular type
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of non-volatile memory may not have a protection algorithm.
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``access``
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is an enumerated type to indicate the organization of the memory
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devices in this memory area. The following is a list of the access
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types supported by the current driver implementation:
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- simple unsigned8
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- simple unsigned16
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- simple unsigned32
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- simple unsigned64
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- single unsigned8 at offset 0 in an unsigned16
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- single unsigned8 at offset 1 in an unsigned16
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- single unsigned8 at offset 0 in an unsigned32
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- single unsigned8 at offset 1 in an unsigned32
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- single unsigned8 at offset 2 in an unsigned32
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- single unsigned8 at offset 3 in an unsigned32
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``depth``
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is the depth of the progamming FIFO on this particular chip. Some
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chips, particularly EEPROMs, have the same programming algorithm but
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vary in the depth of the amount of data that can be programmed in a
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single block.
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``number_of_partitions``
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is the number of logical partitions within this area.
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``Partitions``
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is the address of the table that contains an entry to describe each
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partition in this area. Fields within each element of this table are
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defined as follows:
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``offset``
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is the offset of this partition from the base address of this area.
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``length``
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is the length of this partition.
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By dividing an area of memory into multiple partitions, it is possible to
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easily divide the non-volatile memory for different purposes.
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Initialize the Non-Volatile Memory Driver
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=========================================
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At system initialization, the non-volatile memory driver's initialization entry
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point will be invoked. As part of initialization, the driver will perform
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whatever initializatin is required on each non-volatile memory area.
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The discrete I/O driver may register device names for memory partitions of
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particular interest to the system. Normally this will be restricted to the
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device "/dev/nv_memory" to indicate the entire device driver.
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Disable Read and Write Handlers
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===============================
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Depending on the target's non-volatile memory configuration, it may be possible
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to write to a status register and make the memory area completely inaccessible.
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This is target dependent and beyond the standard capabilities of any memory
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type. The user has the optional capability to provide handlers to disable and
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enable access to a partiticular memory area.
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Open a Particular Memory Partition
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==================================
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This is the driver open call. Usually this call does nothing other than
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validate the minor number.
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With some drivers, it may be necessary to allocate memory when a particular
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device is opened. If that is the case, then this is often the place to do this
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operation.
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Close a Particular Memory Partition
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===================================
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This is the driver close call. Usually this call does nothing.
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With some drivers, it may be necessary to allocate memory when a particular
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device is opened. If that is the case, then this is the place where that
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memory should be deallocated.
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Read from a Particular Memory Partition
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=======================================
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This corresponds to the driver read call. After validating the minor number
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and arguments, this call enables reads from the specified memory area by
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invoking the user supplied "enable reads handler" and then reads the indicated
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memory area. When invoked the ``argument_block`` is actually a pointer to the
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following structure type:
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.. code-block:: c
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typedef struct {
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uint32_t offset;
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void *buffer;
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uint32_t length;
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uint32_t status;
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} Non_volatile_memory_Driver_arguments;
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The driver reads ``length`` bytes starting at ``offset`` into the partition and
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places them at ``buffer``. The result is returned in ``status``.
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After the read operation is complete, the user supplied "disable reads handler"
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is invoked to protect the memory area again.
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Write to a Particular Memory Partition
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======================================
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This corresponds to the driver write call. After validating the minor number
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and arguments, this call enables writes to the specified memory area by
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invoking the "enable writes handler", then unprotecting the memory area, and
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finally actually writing to the indicated memory area. When invoked the
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``argument_block`` is actually a pointer to the following structure type:
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.. code-block:: c
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typedef struct {
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uint32_t offset;
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void *buffer;
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uint32_t length;
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uint32_t status;
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} Non_volatile_memory_Driver_arguments;
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The driver writes ``length`` bytes from ``buffer`` and writes them to the
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non-volatile memory starting at ``offset`` into the partition. The result is
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returned in ``status``.
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After the write operation is complete, the "disable writes handler" is invoked
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to protect the memory area again.
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Erase the Non-Volatile Memory Area
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==================================
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This is one of the IOCTL functions supported by the I/O control device driver
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entry point. When this IOCTL function is invoked, the specified area of
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non-volatile memory is erased.
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