New API call: read disk.

3 files changed, 48 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index a93f72f4..325eb486 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,7 @@ Changes in 3.35:
 
 	  To install ldlinux.sys in a subdirectory, pass the -d
 	  directory option to the SYSLINUX installer.
+	* New API call: read disk.
 
 Changes in 3.31:
 	* The simple menu system (menu.c32 and vesamenu.c32) now
diff --git a/comboot.doc b/comboot.doc
index e7627793..c99522ec 100644
--- a/comboot.doc
+++ b/comboot.doc
@@ -362,8 +362,10 @@ AX=000Ah [2.00]	Get Derivative-Specific Information
 
 	[SYSLINUX, EXTLINUX]
 	Input:	AX	000Ah
+		CL	9 (to get a valid return in CL for all versions)
 	Output:	AL	31h (SYSLINUX), 34h (EXTLINUX)
 		DL	drive number
+		CL	sector size as a power of 2 (9 = 512 bytes) [3.35]
 		ES:BX	pointer to partition table entry (if DL >= 80h)
 
 		Note: This function was broken in EXTLINUX 3.00-3.02.
@@ -413,6 +415,7 @@ AX=000Ah [2.00]	Get Derivative-Specific Information
 	Input:	AX	000Ah
 	Output:	AL	33h (ISOLINUX)
 		DL	drive number
+		CL	11 (sector size as a power of 2) [3.35]
 		ES:BX	pointer to El Torito spec packet
 
 		Note: Some very broken El Torito implementations do
@@ -718,3 +721,23 @@ AX=0018h [3.30]	Query custom font
 	This call queries if a custom display font has been loaded via
 	the "font" configuration file command.  If no custom font has
 	been loaded, AL contains zero.
+
+
+AX=0019h [3.35] Read disk [SYSLINUX, ISOLINUX, EXTLINUX]
+	Input:	AX	0019h
+		EDX	Sector number
+		ESI	Reserved - MUST BE ZERO
+		EDI	Reserved - MUST BE ZERO
+		CX	Sector count
+		ES:BX	Buffer address
+	Output:	None
+
+	Read disk blocks from the active filesystem (partition); for
+	disks, sector number zero is the boot sector.  For ISOLINUX,
+	this call reads the CD-ROM.
+
+	For compatiblity with all systems, the buffer should
+	*neither* cross 64K boundaries, *nor* wrap around the segment.
+
+	This routine reports "boot failed" (and does not return) on
+	disk error.
diff --git a/comboot.inc b/comboot.inc
index 5fda9687..fcaa3a7a 100644
--- a/comboot.inc
+++ b/comboot.inc
@@ -466,6 +466,7 @@ comapi_derinfo:
 		mov P_DL,al
 		mov P_ES,cs
 		mov P_BX,PartInfo
+		mov P_CL,SECTOR_SHIFT
 %elif IS_PXELINUX
 		mov ax,[APIVer]
 		mov P_DX,ax
@@ -482,6 +483,7 @@ comapi_derinfo:
 		mov P_DL,al
 		mov P_ES,cs
 		mov P_BX,spec_packet
+		mov P_CL,SECTOR_SHIFT
 %endif
 		clc
 		ret
@@ -769,7 +771,27 @@ comapi_userfont:
 		mov P_AL,al
 		ret
 		
-
+;
+; INT 22h AX=0019h  Read disk
+;
+%if IS_SYSLINUX || IS_MDSLINUX || IS_ISOLINUX || IS_EXTLINUX
+comapi_readdisk:
+		mov esi,P_ESI		; Enforce ESI == EDI == 0, these
+		or esi,P_EDI		; are reserved for future expansion
+		jnz .err
+		mov eax,P_EDX
+		mov bp,P_CX
+		mov es,P_ES
+		mov bx,P_BX
+		call getlinsec
+		clc
+		ret
+.err:
+		stc
+		ret
+%else
+comapi_readdisk	equ comapi_err
+%endif
 
 		section .data
 
@@ -818,6 +840,7 @@ int22_table:
 		dw comapi_runkernel	; 0016 run kernel image
 		dw comapi_usingvga	; 0017 report video mode change
 		dw comapi_userfont	; 0018 query custom font
+		dw comapi_readdisk	; 0019 read disk
 int22_count	equ ($-int22_table)/2
 
 APIKeyWait	db 0