Changes between Version 24 and Version 25 of FSDesign

Timestamp:

2009-11-17T19:37:09Z (14 years ago)

Author:

Jakub Jermář

Comment:

—

FSDesign

@@ -163 +163 @@
 As mentioned above, each endpoint file system server needs to implement the VFS output protocol. Through the polymorphism this offers, HelenOS currently supports the following file system types (and we believe that more can be added):
 
- TMPFS::
+ '''TMPFS'''::
  A custom memory based file system without an on-disk format and permanent storage.
 
- FAT16::
+ '''FAT16'''::
  A well known, non-Unix like file system with simple on-disk format.
 
- DEVFS::
+ '''DEVFS'''::
  A custom pseudo file system for representing devices in the file system.
 
+Especially the servers for file systems with permanent storage, such as FAT16, need to communicate with the underlying block device. Therefore, there needs to be a mechanism to connect the endpoint file system server with the block device. This mechanism is provided by the DEVMAP server which registers all the device driver servers and lets their clients to connect to them using the device handle. This is how the endpoint file system server establishes a connection to the underlying block device via the libblock library, which itself uses the standard library's interface to DEVMAP:
+
+{{{
+        #include <ipc/devmap.h>
+....
+        dev_handle_t dev_handle;
+....
+        int dev_phone = devmap_device_connect(dev_handle, IPC_FLAG_BLOCKING);
+        if (dev_phone < 0) {
+                /* handle error */
+        }
+}}}
+