Changes between Version 6 and Version 7 of TBR/UserManual/Using_the_RTEMS_DOS_File_System

Timestamp:

09/13/08 08:21:45 (16 years ago)

Author:

ChrisJohns

Comment:

Update the RAM Disk usage

TBR/UserManual/Using_the_RTEMS_DOS_File_System

@@ -80 +80 @@
    return 1;
  }
-  
+ 
  printf ("successful\n");
 
@@ -102 +102 @@
    return 1;
  }
+= RAM Disk =
+
+
+The RAM disk driver supports a single continuous memory region as a disk. There is no partitions. You can specify the location of the memory to use or the driver can allocate the memory from the heap. The memory is not initialised so you need to format the disk once you have created it.
+
+The RAM disk has a 1:1 block mapping. Block 0 is the first block in the memory region. There is not checking on blocks so a block of memory that survives reset and even power loss such as static RAM cannot be checked for a valid disk image. You should considering using the NV Disk driver in this case.
+
+To configure a RAM disk add this following to a source file in your application. The configuration items are:
+
+# Block size. This is normally 512 for the MSDOS file-system
+# Number of blocks in the disk drive. The memory size is the block size multiplied by the number of blocks
+# The location. If NULL the heap is used.
+
+An example is:
+
+ /**
+  * The RAM Disk configuration.
+  */
+ rtems_ramdisk_config rtems_ramdisk_configuration[] =
+
+ {
+   {
+     block_size: 512,
+     block_num:  4000,
+     location:   NULL
+   }
+ };
+ 
+ /**
+  * The number of RAM Disk configurations.
+  */
+ size_t rtems_ramdisk_configuration_size = 1;
+
+To use the RAM disk you need to register the driver. For example:
+
+  rtems_driver_address_table rtems_flashdisk_io_ops = 
+     RAMDISK_DRIVER_TABLE_ENTRY;
+
+  rtems_device_major_number major;
+  rtems_status_code         sc;
   
- return 0;
+  /*
+   * Register the RAM Disk driver.
+   */
+  printf ("Register RAM Disk Driver: ");
+  sc = rtems_io_register_driver (RTEMS_DRIVER_AUTO_MAJOR,
+                                 &rtems_ramdisk_io_ops,
+                                 &major);
+  if (sc != RTEMS_SUCCESSFUL)
+  {
+    printf ("error: ramdisk driver not initialised: %s\n",
+            rtems_status_text (sc));
+    return 1;
+  }
+  
+  printf ("successful\n");
+
+Once the driver has been register you can mount the disk using the shell command of:
+
+ mkdir rd
+ mount -t msdos /dev/ramdisk0 /rd
+
+The code to mount the same device to an existing {{{/rd</code> directory is:
+
+ #include <rtems/dosfs.h>
+ #include <rtems/fsmount.h>
+ 
+ rtems_filesystem_mount_table_entry_t* mt_entry;
+  
+ if (mount (&mt_entry, &msdos_ops, options, "/dev/ramdisk0", "/rd") < 0)
+ {
+   fprintf (stderr, "mount: mount failed: %s\n", strerror (errno));
+   return 1;
+ }
+  = NV Disk =