The filesystem table is an array of entries that describe each filesystem implementation that is part of the system image. Each resident filesystem should export an entry to this table using the FSTAB_ENTRY() macro.
Note: At present we do not support dynamic addition or removal of table entries. However, an API similar to
mount()would allow new entries to be added to the table.
The table entries are described by the following structure:
struct cyg_fstab_entry
{
const char *name; // filesystem name
CYG_ADDRWORD data; // private data value
cyg_uint32 syncmode; // synchronization mode
int (*mount) ( cyg_fstab_entry *fste, cyg_mtab_entry *mte );
int (*umount) ( cyg_mtab_entry *mte );
int (*open) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name,
int mode, cyg_file *fte );
int (*unlink) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name );
int (*mkdir) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name );
int (*rmdir) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name );
int (*rename) ( cyg_mtab_entry *mte, cyg_dir dir1, const char *name1,
cyg_dir dir2, const char *name2 );
int (*link) ( cyg_mtab_entry *mte, cyg_dir dir1, const char *name1,
cyg_dir dir2, const char *name2, int type );
int (*opendir) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name,
cyg_file *fte );
int (*chdir) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name,
cyg_dir *dir_out );
int (*stat) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name,
struct stat *buf);
int (*getinfo) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name,
int key, char *buf, int len );
int (*setinfo) ( cyg_mtab_entry *mte, cyg_dir dir, const char *name,
int key, char *buf, int len );
}; |
The name field points to a string that
identifies this filesystem implementation. Typical values might be
"romfs", "msdos", "ext2" etc.
The data field contains any private data
that the filesystem needs, perhaps the root of its data structures.
The syncmode field contains a description of
the locking protocol to be used when accessing this filesystem. It
will be described in more detail in Chapter 19.
The remaining fields are pointers to functions that implement filesystem operations that apply to files and directories as whole objects. The operation implemented by each function should be obvious from the names, with a few exceptions:
The opendir() function pointer opens a directory
for reading. See Chapter 18 for details.
The getinfo() and
setinfo() function pointers provide support for
various minor control and information functions such as
pathconf() and access().
With the exception of the mount() and
umount() functions, all of these functions
take three standard arguments, a pointer to a mount table entry (see
later) a directory pointer (also see later) and a file name relative
to the directory. These should be used by the filesystem to locate the
object of interest.