Changes between Version 9 and Version 10 of TBR/UserManual/Using_the_RTEMS_DOS_File_System

Timestamp:

Oct 22, 2008, 4:46:57 AM (12 years ago)

Author:

ChrisJohns

Comment:

Start adding some NV disk info.

TBR/UserManual/Using_the_RTEMS_DOS_File_System

@@ -182 +182 @@
  }
 = NV Disk =
+
+
+The Non-Volatile Disk driver supports more than one device per disk. A table of device descriptions describes the devices in a disk and you can have more than one NV disk active at once.
+
+The NV Disk is suitable for devices that byte or word reprogrammable and retain data over a power loss or target reset. For example battery backed up static RAM or EEPROM type devices. The driver performs no wear levelling as the disk blocks are mapped 1:1 with the devices in the device description table. There is no remapping of blocks.
+
+A device is describing using the {{{rtems_nvdisk_device_desc</code> structure. It is located in the <file>nvdisk.h</file> header file. The structure is:
+
+ /**
+  * NV Device Descriptor holds the description of a device that is
+  * part of the NV disk.
+  *
+  * Typically this structure is part of a table of the device which
+  * is referenced in the nvdisk configuration table.
+  * The reference is kept in the driver and used all the time to
+  * manage the nv device, therefore it must always exist.
+  */
+ typedef struct rtems_nvdisk_device_desc
+ {
+   uint32_t                            flags;  /**< Private user flags. */
+   uint32_t                            base;   /**< Base address of the device. */
+   uint32_t                            size;   /**< Size of the device. */
+   const rtems_nvdisk_driver_handlers* nv_ops; /**< Device handlers. */
+ } rtems_nvdisk_device_desc;
+
+The {{{flags</code> field provides a private set of flags a specific low level device handlers for a device may need. The {{{base</base> is the base address of the device. Its definition depends on the low level device handlers for a specific device. The {{{size</code> field defines the number of bytes of storage the device provides in bytes. This is the raw number of bytes available to the driver. The {{{nv_ops</code> is a set of handlers for the specific device.
+
+The NV Disk device requires a set of handlers for each type of device. The handles can manage more than one device in a disk or disks. The handlers are:
+
+{{{int (*read) (uint32_t device, uint32_t flags, uint32_t base, uint32_t offset, void* buffer, uint32_t size);</code>
+
+The <tt>nvdisk-sram.h</tt> provides a set of handlers suitable for static RAM.