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XFS Internals

This document describes the internal architecture of the XFS filesystem, including register layout, command protocol, and module implementation details.

XFS Registers​

XFS uses page 0x49 (XFS_SPECTRANET_PAGE) for its registers. When Page A is mapped to 0x49, the XFS registers are accessible at address 0x1000.

The XFS registers structure (xfs_registers_t) includes:

  • Command register: Command to execute (MOUNT, OPEN, READ, etc.)
  • Status register: Current status (IDLE, BUSY, COMPLETE, ERROR)
  • Result register: Error code or success indicator
  • File handle: Handle for file/directory operations
  • Arguments: Command-specific arguments
  • Workspace: Data transfer buffer (1024 bytes)

XFS Commands​

  • XFS_CMD_MOUNT (1) - Mount filesystem
  • XFS_CMD_OPEN (2) - Open file
  • XFS_CMD_READ (3) - Read from file
  • XFS_CMD_WRITE (4) - Write to file
  • XFS_CMD_CLOSE (5) - Close file
  • XFS_CMD_OPENDIR (6) - Open directory
  • XFS_CMD_READDIR (7) - Read directory entry
  • XFS_CMD_CLOSEDIR (8) - Close directory
  • XFS_CMD_STAT (9) - Get file information
  • XFS_CMD_UNLINK (10) - Delete file
  • XFS_CMD_MKDIR (11) - Create directory
  • XFS_CMD_RMDIR (12) - Remove directory
  • XFS_CMD_CHDIR (13) - Change directory
  • XFS_CMD_GETCWD (14) - Get current directory
  • XFS_CMD_RENAME (15) - Rename file
  • XFS_CMD_LSEEK (16) - Seek in file

XFS Module​

The XFS module is a Spectranet ROM module that implements the VFS interface. It:

  • Intercepts mount requests for "xfs" protocol
  • Communicates with Spectranext cartridge via XFS registers
  • Provides standard VFS operations to Spectrum programs

Next Steps​