[syslinux:master] comboot: allow the read disk API call to specify a 64-bit LBA

syslinux-bot for H. Peter Anvin hpa at linux.intel.com
Mon Jun 21 15:18:17 PDT 2010


Commit-ID:  2f712545dd82f5906ec930b643d44e8b12295682
Gitweb:     http://syslinux.zytor.com/commit/2f712545dd82f5906ec930b643d44e8b12295682
Author:     H. Peter Anvin <hpa at linux.intel.com>
AuthorDate: Mon, 21 Jun 2010 15:12:48 -0700
Committer:  H. Peter Anvin <hpa at linux.intel.com>
CommitDate: Mon, 21 Jun 2010 15:16:33 -0700

comboot: allow the read disk API call to specify a 64-bit LBA

We already had two MBZ fields reserved, so use one of them to expand
into a 64-bit LBA.

Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>


---
 core/comboot.inc |    4 ++--
 doc/comboot.txt  |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/core/comboot.inc b/core/comboot.inc
index 0c9956a..91cc15a 100644
--- a/core/comboot.inc
+++ b/core/comboot.inc
@@ -837,10 +837,10 @@ comapi_userfont:
 ;
 %if IS_SYSLINUX || IS_ISOLINUX || IS_EXTLINUX
 comapi_readdisk:
-		mov esi,P_ESI		; Enforce ESI == EDI == 0, these
-		or esi,P_EDI		; are reserved for future expansion
+		cmp P_EDI,0		; Reserved for future expansion
 		jnz .err
 		mov eax,P_EDX
+		mov edx,P_ESI
 		mov es,P_ES
 		mov bx,P_BX
 		mov bp,P_CX		; WE CANNOT use P_* after touching bp!
diff --git a/doc/comboot.txt b/doc/comboot.txt
index 036bd78..9e9f99a 100644
--- a/doc/comboot.txt
+++ b/doc/comboot.txt
@@ -832,8 +832,8 @@ AX=0018h [3.30]	Query custom font
 
 AX=0019h [3.50] Read disk [SYSLINUX, ISOLINUX, EXTLINUX]
 	Input:	AX	0019h
-		EDX	Sector number
-		ESI	Reserved - MUST BE ZERO
+		EDX	Sector number (LSW)
+		ESI	Sector number (MSW) [4.00]
 		EDI	Reserved - MUST BE ZERO
 		CX	Sector count
 		ES:BX	Buffer address



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