See also: Kernel Index, Drivers, Syscall

This directory provides the filesystem and file-descriptor pipeline.

Components

Virtual Filesystem Switch (VFS)

vfs/vfs.c — Dispatches file operations to concrete filesystems. Uses a VFS_Operations struct with Linux-style callbacks:

  • open, create, readdir, read, write, seek, close

  • get_size, delete, access, chmod, chown

  • Mount operations: FS_Mount(), FS_Umount()

FAT Filesystem

fat/fat.c — Full FAT12/16/32 implementation supporting:

  • File open, read, write, seek

  • File creation, deletion, truncation

  • Directory read/write, directory entry creation

  • Multi-cluster file support

  • VFS integration via FAT_GetVFSOperations()

Device Filesystem (devfs)

devfs/devfs.c — In-memory device filesystem exposing:

  • /dev/tty0 — Terminal device

  • /dev/null — Null device (discards writes, returns EOF on read)

  • /dev/zero — Zero device (returns null bytes on read)

  • Dynamic device registration/unregistration/enumeration API

File Descriptor Layer

fd/fd.c — Per-process file descriptor table (16 entries per process).

  • FD_Open(), FD_Close(), FD_Read(), FD_Write(), FD_Lseek()

  • FileDescriptor struct: path, offset, readable/writable flags, inode, ref_count

Disk Abstraction

disk/ — Low-level disk and partition handling:

  • disk.c — Disk struct, sector read/write, disk scanning

  • mbr.c — Master Boot Record parsing

  • vbr.c — Volume Boot Record parsing

  • partition.c — Partition metadata (offset, size, type, UUID, label)

Shared Types

misc/fs_types.h — FilesystemType enum: FAT12=1, FAT16=2, FAT32=3, EXT2=4, DEVFS=5

misc/fs.c — FS_Initialize() — initializes devfs and scans disks

misc/std_dev.c — Standard device node creation

Key Headers

  • include/fs/fs.h — Public filesystem API

  • kernel/fs/vfs/vfs.h — VFS internal interface

  • kernel/fs/devfs/devfs.h — Device filesystem API

  • kernel/fs/fd/fd.h — File descriptor API

Typical Work in This Area

  • Add filesystem operations and metadata support

  • Implement Ext2 filesystem driver (enum exists, no implementation)

  • Add FAT LFN (Long File Name) support

  • Improve mount and partition probing logic

  • Fix descriptor and seek/read/write semantics

Revision History

v2.0

Updated for v0.28: detailed component breakdown with function listings, added devfs, fd layer, disk abstraction, shared types

v1.0

Initial filesystem subsystem summary