COMBOOT API: Add calls for directory functions; Implement for FAT

COMBOOT API: Add calls for directory functions; Implement most only
for FAT (SYSLINUX).

Uses INT 22h AX= 001Fh, 0020h, 0021h and 0022h to prepare for the
COM32 C functions getcwd(), opendir(), readdir(), and closedir(),
respectively.  INT22h, AX=001Fh will return a valid value for all
variants.  INT22h, AX= 0020h, 0021h, and 0022h are only implemented
for SYSLINUX while other variants will call comapi_err for these 3.

Signed-off-by: Gene Cumm <gene.cumm@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/doc/comboot.txt b/doc/comboot.txt
index 53295020..387303d3 100644
--- a/doc/comboot.txt
+++ b/doc/comboot.txt
@@ -921,3 +921,46 @@ AX=001Eh [3.74] Keyboard remapping table
 	version, the format code is always 1 and the length is always
 	256.  This version can be updated simply by overwriting the version
 	in memory; this may not be true in the future.
+
+
+AX=001Fh [BETA-3.74+]	Get current working directory
+	Input:	AX	0001Eh
+	Output:	ES:BX	null-terminated directory name string
+
+	Returns the current working directory.  For SYSLINUX, ISOLINUX,
+	and PXELINUX, this will be an absolute path.  For EXTLINUX, it
+	currently returns "./".
+
+
+AX=0020h [BETA-3.74+] Open directory
+	Input:	AX	001Fh
+		ES:SI	/-null-terminated directory name
+	Output:	SI	directory handle
+		EAX	clobbered
+
+	Open a directory for reading.  Directory name must have a trailing
+	 "/" before the null (otherwise, you're looking for a file)(This
+	may change as this is a BETA call).
+
+
+AX=0021h [BETA-3.74+] Read directory
+	Input:	AX	0020h
+		SI	directory handle
+		ES:DI	buffer for file name
+	Output:	DL	Type of file
+		SI	directory handle, or 0 if end of directory was reached
+		EAX	Size of file
+		EBX	Inode of file
+
+	Read one filename from the directory, incrementing the directory
+	structure at SI as appropriate, storing the filename into the buffer
+	at ES:DI, and returning the type of the file in DL, the file length
+	in EAX, the INode/file number in EBX and the updated directory handle.
+
+
+AX=0022h [BETA-3.74+] Close directory
+	Input:	AX	001Fh
+		SI	directory handle
+	Output	SI	0
+
+	Closes a directory.