Re: [PATCH] Kernel support for VESA Bios Extension

["Vesa Jääskeläinen" <chaac@nic.fi>]

[-- Attachment #1: Type: text/plain, Size: 862 bytes --]

Marco Gerards wrote:

>>I would like to hear comments about the patch. I tried to implement
>>most commonly needed functions, so you can't do everything with
>>this. As I didn't need to use every function in my frame buffer
>>console test, some things might not work. But I tried to make my best
>>to proof read every function.
> 
> Can you please make sure you are using the GCS for coding style?
> Please have a look at the other sourcecode and the GCS (GNU Coding
> Standards) first:
> 
> http://www.gnu.org/prep/standards/
> 
> It is important for us to have a single and consistent coding style.
> If you have questions about either GRUB or the coding style you are of
> course free to ask.

Perhaps this is a bit closer to requirement?

If there still are issues on formatting could you specify what issues 
you are thinking on.

Thanks,
Vesa Jääskeläinen

[-- Attachment #2: grub2_i386_vbe.diff --]
[-- Type: text/plain, Size: 18972 bytes --]

diff -ruN grub2/ChangeLog grub2.vbe/ChangeLog
--- grub2/ChangeLog	2005-07-13 01:36:43.000000000 +0300
+++ grub2.vbe/ChangeLog	2005-07-16 15:07:01.132381816 +0300
@@ -1,3 +1,21 @@
+2005-07-14  Vesa Jaaskelainen  <chaac@nic.fi>
+
+	* conf/i386-pc.rmk (kernel_img_HEADERS): Added machine/vbe.h.
+	* kern/i386/pc/startup.S: Updated Global Descriptor table's
+	descriptions.
+	(grub_vbe_get_controller_info): New function.
+	(grub_vbe_get_mode_info): Likewise.
+	(grub_vbe_set_mode): Likewise.
+	(grub_vbe_get_mode): Likewise.
+	(grub_vbe_set_memory_window): Likewise.
+	(grub_vbe_get_memory_window): Likewise.
+	(grub_vbe_set_scanline_length): Likewise.
+	(grub_vbe_get_scanline_length): Likewise.
+	(grub_vbe_set_display_start): Likewise.
+	(grub_vbe_get_display_start): Likewise.
+	(grub_vbe_set_palette_data): Likewise.
+	* include/grub/i386/pc/vbe.h: New file.
+
 2005-07-12  Hollis Blanchard  <hollis@penguinppc.org>
 
 	* disk/powerpc/ieee1275/ofdisk.c (grub_ofdisk_open): dprintf the
diff -ruN grub2/conf/i386-pc.rmk grub2.vbe/conf/i386-pc.rmk
--- grub2/conf/i386-pc.rmk	2005-07-10 10:57:49.000000000 +0300
+++ grub2.vbe/conf/i386-pc.rmk	2005-07-15 18:10:05.000000000 +0300
@@ -33,7 +33,8 @@
 	file.h fs.h kernel.h loader.h misc.h mm.h net.h rescue.h symbol.h \
 	term.h types.h machine/biosdisk.h machine/boot.h \
 	machine/console.h machine/init.h machine/memory.h \
-	machine/loader.h partition.h pc_partition.h machine/time.h machine/vga.h
+	machine/loader.h partition.h pc_partition.h machine/time.h machine/vga.h \
+	machine/vbe.h
 kernel_img_CFLAGS = $(COMMON_CFLAGS)
 kernel_img_ASFLAGS = $(COMMON_ASFLAGS)
 kernel_img_LDFLAGS = -nostdlib -Wl,-N,-Ttext,8200
diff -ruN grub2/include/grub/i386/pc/vbe.h grub2.vbe/include/grub/i386/pc/vbe.h
--- grub2/include/grub/i386/pc/vbe.h	1970-01-01 02:00:00.000000000 +0200
+++ grub2.vbe/include/grub/i386/pc/vbe.h	2005-07-16 17:21:40.815083344 +0300
@@ -0,0 +1,180 @@
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2005  Free Software Foundation, Inc.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef GRUB_VBE_MACHINE_HEADER
+#define GRUB_VBE_MACHINE_HEADER	1
+
+#include <grub/symbol.h>
+#include <grub/types.h>
+
+/*
+ * Note:
+ *
+ * Please refer to VESA BIOS Extension 3.0 Specification for more descriptive
+ * meanings of following structures and how they should be used.
+ *
+ * I have tried to maintain field name comatibility against specification while
+ * following naming convetions used in GRUB.
+ */
+
+typedef grub_uint32_t 	grub_vbe_farptr_t;
+typedef grub_uint32_t	grub_vbe_physptr_t;
+typedef grub_uint32_t	grub_vbe_status_t;
+
+struct grub_vbe_info_block
+{
+  grub_uint8_t signature[4];
+  grub_uint16_t version;
+
+  grub_vbe_farptr_t oem_string_ptr;
+  grub_uint32_t capabilities;
+  grub_vbe_farptr_t video_mode_ptr;
+  grub_uint16_t total_memory;
+
+  grub_uint16_t oem_software_rev;
+  grub_vbe_farptr_t oem_vendor_name_ptr;
+  grub_vbe_farptr_t oem_product_name_ptr;
+  grub_vbe_farptr_t oem_product_rev_ptr;
+
+  grub_uint8_t reserved[222];
+
+  grub_uint8_t oem_data[256];
+} __attribute__ ((packed));
+
+struct grub_vbe_mode_info_block
+{
+  /* Mandory information for all VBE revisions */
+  grub_uint16_t mode_attributes;
+  grub_uint8_t win_a_attributes;
+  grub_uint8_t win_b_attributes;
+  grub_uint16_t win_granularity;
+  grub_uint16_t win_size;
+  grub_uint16_t win_a_segment;
+  grub_uint16_t win_b_segment;
+  grub_vbe_farptr_t win_func_ptr;
+  grub_uint16_t bytes_per_scan_line;
+
+  /* Mandory information for VBE 1.2 and above */
+  grub_uint16_t x_resolution;
+  grub_uint16_t y_resolution;
+  grub_uint8_t x_char_size;
+  grub_uint8_t y_char_size;
+  grub_uint8_t number_of_planes;
+  grub_uint8_t bits_per_pixel;
+  grub_uint8_t number_of_banks;
+  grub_uint8_t memory_model;
+  grub_uint8_t bank_size;
+  grub_uint8_t number_of_image_pages;
+  grub_uint8_t reserved;
+
+  /* Direct Color fields (required for direct/6 and YUV/7 memory models) */
+  grub_uint8_t red_mask_size;
+  grub_uint8_t red_field_position;
+  grub_uint8_t green_mask_size;
+  grub_uint8_t green_field_position;
+  grub_uint8_t blue_mask_size;
+  grub_uint8_t blue_field_position;
+  grub_uint8_t rsvd_mask_size;
+  grub_uint8_t rsvd_field_position;
+  grub_uint8_t direct_color_mode_info;
+
+  /* Mandory information for VBE 2.0 and above */
+  grub_vbe_physptr_t phys_base_addr;
+  grub_uint32_t reserved2;
+  grub_uint16_t reserved3;
+
+  /* Mandory information for VBE 3.0 and above */
+  grub_uint16_t lin_bytes_per_scan_line;
+  grub_uint8_t bnk_number_of_image_pages;
+  grub_uint8_t lin_number_of_image_pages;
+  grub_uint8_t lin_red_mask_size;
+  grub_uint8_t lin_red_field_position;
+  grub_uint8_t lin_green_mask_size;
+  grub_uint8_t lin_green_field_position;
+  grub_uint8_t lin_blue_mask_size;
+  grub_uint8_t lin_blue_field_position;
+  grub_uint8_t lin_rsvd_mask_size;
+  grub_uint8_t lin_rsvd_field_position;
+  grub_uint32_t max_pixel_clock;
+
+  /*
+   * Reserved field to make structure to be 256 bytes long, VESA BIOS 
+   * Extension 3.0 Specification says to reserve 189 bytes here but 
+   * that doesn't make structure to be 256 bytes. So additional one is 
+   * added here.
+   */
+  grub_uint8_t reserved4[189+1];
+} __attribute__ ((packed));
+
+struct grub_vbe_crtc_info_block
+{
+  grub_uint16_t horizontal_total;
+  grub_uint16_t horizontal_sync_start;
+  grub_uint16_t horizontal_sync_end;
+  grub_uint16_t vertical_total;
+  grub_uint16_t vertical_sync_start;
+  grub_uint16_t vertical_sync_end;
+  grub_uint8_t flags;
+  grub_uint32_t pixel_clock;
+  grub_uint16_t refresh_rate;
+  grub_uint8_t reserved[40];
+} __attribute__ ((packed));
+
+struct grub_vbe_palette_data
+{
+  grub_uint8_t blue;
+  grub_uint8_t green;
+  grub_uint8_t red;
+  grub_uint8_t aligment;
+} __attribute__ ((packed));
+
+/* Call VESA BIOS 0x4f00 to get VBE Controller Information, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_get_controller_info) (struct grub_vbe_info_block *controller_info);
+
+/* Call VESA BIOS 0x4f01 to get VBE Mode Information, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_get_mode_info) (grub_uint32_t mode, struct grub_vbe_mode_info_block *mode_info);
+
+/* Call VESA BIOS 0x4f02 to set video mode, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_set_mode) (grub_uint32_t mode, struct grub_vbe_crtc_info_block *crtc_info);
+
+/* Call VESA BIOS 0x4f03 to return current VBE Mode, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_get_mode) (grub_uint32_t *mode);
+
+/* Call VESA BIOS 0x4f05 to set memory window, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_set_memory_window) (grub_uint32_t window, grub_uint32_t position);
+
+/* Call VESA BIOS 0x4f05 to return memory window, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_get_memory_window) (grub_uint32_t window, grub_uint32_t *position);
+
+/* Call VESA BIOS 0x4f06 to set scanline length (in bytes), return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_set_scanline_length) (grub_uint32_t length);
+
+/* Call VESA BIOS 0x4f06 to return scanline length (in bytes), return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_get_scanline_length) (grub_uint32_t *length);
+
+/* Call VESA BIOS 0x4f07 to set display start, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_set_display_start) (grub_uint32_t x, grub_uint32_t y);
+
+/* Call VESA BIOS 0x4f07 to get display start, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_get_display_start) (grub_uint32_t *x, grub_uint32_t *y);
+
+/* Call VESA BIOS 0x4f09 to set palette data, return status */
+grub_vbe_status_t EXPORT_FUNC(grub_vbe_set_palette_data) (grub_uint32_t color_count, grub_uint32_t start_index, struct grub_vbe_palette_data *palette_data);
+
+#endif /* ! GRUB_VBE_MACHINE_HEADER */
diff -ruN grub2/kern/i386/pc/startup.S grub2.vbe/kern/i386/pc/startup.S
--- grub2/kern/i386/pc/startup.S	2004-04-04 16:46:02.000000000 +0300
+++ grub2.vbe/kern/i386/pc/startup.S	2005-07-16 17:17:21.471509560 +0300
@@ -1,6 +1,6 @@
 /*
  *  GRUB  --  GRand Unified Bootloader
- *  Copyright (C) 1999,2000,2001,2002,2003 Free Software Foundation, Inc.
+ *  Copyright (C) 1999,2000,2001,2002,2003,2005 Free Software Foundation, Inc.
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -219,11 +219,11 @@
  * 31          24         19   16                 7           0
  * ------------------------------------------------------------
  * |             | |B| |A|       | |   |1|0|E|W|A|            |
- * | BASE 31..24 |G|/|0|V| LIMIT |P|DPL|  TYPE   | BASE 23:16 |
+ * | BASE 31..24 |G|/|L|V| LIMIT |P|DPL|  TYPE   | BASE 23:16 |  4
  * |             | |D| |L| 19..16| |   |1|1|C|R|A|            |
  * ------------------------------------------------------------
  * |                             |                            |
- * |        BASE 15..0           |       LIMIT 15..0          |
+ * |        BASE 15..0           |       LIMIT 15..0          |  0
  * |                             |                            |
  * ------------------------------------------------------------
  *
@@ -236,19 +236,31 @@
 	.word	0, 0
 	.byte	0, 0, 0, 0
 
-	/* code segment */
+	/* -- code segment --
+	 * base = 0x00000000, limit = 0xFFFFF (4 KiB Granularity), present
+	 * type = 32bit code execute/read, DPL = 0
+	 */
 	.word	0xFFFF, 0
 	.byte	0, 0x9A, 0xCF, 0
 
-	/* data segment */
+	/* -- data segment --
+	 * base = 0x00000000, limit 0xFFFFF (4 KiB Granularity), present
+	 * type = 32 bit data read/write, DPL = 0 
+	 */
 	.word	0xFFFF, 0
 	.byte	0, 0x92, 0xCF, 0
 
-	/* 16 bit real mode CS */
+	/* -- 16 bit real mode CS --
+	 * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present
+	 * type = 16 bit code execute/read only/conforming, DPL = 0
+	 */
 	.word	0xFFFF, 0
 	.byte	0, 0x9E, 0, 0
 
-	/* 16 bit real mode DS */
+	/* -- 16 bit real mode DS --
+	 * base = 0x00000000, limit 0x0FFFF (1 B Granularity), present
+	 * type = 16 bit data read/write, DPL = 0
+	 */
 	.word	0xFFFF, 0
 	.byte	0, 0x92, 0, 0
 
@@ -1594,3 +1606,414 @@
 	popl	%ebx
 	popl	%ebp
 	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_get_controller_info (struct grub_vbe_info_block *controller_info)
+ *
+ * Register allocations for parameters:
+ * %eax		*controller_info
+ */
+FUNCTION(grub_vbe_get_controller_info)
+	pushl	%ebp
+	pushl	%edi
+
+	movw	%ax, %di		/* store *controller_info to edx:di */
+	xorw	%ax, %ax
+	shrl	$4, %eax
+	mov	%eax, %edx		/* prot_to_real destroys %eax */
+	
+	call	prot_to_real
+	.code16
+
+	pushw	%es
+
+	movw	%dx, %es		/* *controller_info is now on es:di */
+	movw	$0x4f00, %ax
+	int	$0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	popw	%es
+
+	DATA32 call	real_to_prot
+	.code32
+
+	movl	%edx, %eax
+	andl	$0x0FFFF, %eax		/* return value in %eax */
+	
+	popl	%edi
+	popl	%ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_get_mode_info (grub_uint32_t mode,
+ *					     struct grub_vbe_mode_info_block *mode_info)
+ *
+ * Register allocations for parameters:
+ * %eax		mode
+ * %edx		*mode_info
+ */
+FUNCTION(grub_vbe_get_mode_info)
+	pushl   %ebp
+	pushl   %edi
+
+	movl	%eax, %ecx		/* store mode number to %ecx */
+
+	movw    %dx, %di		/* store *mode_info to edx:di*/
+	xorw    %dx, %dx
+	shrl    $4, %edx
+
+	call    prot_to_real
+	.code16
+
+	pushw   %es
+
+	movw    %dx, %es		/* *mode_info is now on es:di */
+	movw    $0x4f01, %ax
+	int     $0x10
+
+	movw    %ax, %dx        	/* real_to_prot destroys %eax */
+
+	popw    %es
+
+	DATA32 call     real_to_prot
+	.code32
+
+	movl    %edx, %eax
+	andl    $0x0FFFF, %eax  	/* return value in %eax */
+
+	popl    %edi
+	popl    %ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_set_mode (grub_uint32_t mode,
+ *					struct grub_vbe_crtc_info_block *crtc_info)
+ *
+ * Register allocations for parameters:
+ * %eax		mode
+ * %edx		*crtc_info
+ */
+FUNCTION(grub_vbe_set_mode)
+	pushl	%ebp
+	pushl	%ebx
+
+	movl	%eax, %ebx		/* store mode in ebx */
+
+	movw    %dx, %di		/* store *crtc_info to edx:di*/
+	xorw    %dx, %dx
+	shrl    $4, %edx
+
+	call    prot_to_real
+	.code16
+
+	pushw   %es
+
+	movw    %dx, %es		/* *crtc_info is now on es:di */
+
+	movw	$0x4f02, %ax
+	int	$0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	popw	%es
+
+	DATA32 call	real_to_prot
+	.code32
+	
+	movw	%dx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl	%ebx
+	popl	%ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_get_mode (grub_uint32_t *mode)
+ *
+ * Register allocations for parameters:
+ * %eax		*mode
+ */
+FUNCTION(grub_vbe_get_mode)
+	pushl   %ebp
+	pushl   %ebx
+	pushl	%eax			/* push *mode to stack */
+
+	call    prot_to_real
+	.code16
+
+	movw    $0x4f03, %ax
+	int     $0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	DATA32 call     real_to_prot
+	.code32
+
+	popl	%edi			/* pops *mode from stack to %edi */
+	andl	$0xFFFF, %ebx
+	movl	%ebx, (%edi)
+
+	movw	%dx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl    %ebx
+	popl    %ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_set_memory_window (grub_uint32_t window,
+ *						 grub_uint32_t position);
+ *
+ * Register allocations for parameters:
+ * %eax		window
+ * %edx		position
+ */
+FUNCTION(grub_vbe_set_memory_window)
+	pushl	%ebp
+	pushl	%ebx
+
+	movl	%eax, %ebx
+
+	call	prot_to_real
+	.code16
+
+	movw	$0x4f05, %ax
+	andw	$0x00ff, %bx		/* BL = window, BH = 0, Set memory window */
+	int	$0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	DATA32 call	real_to_prot
+	.code32
+	
+	movw	%dx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl	%ebx
+	popl	%ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_get_memory_window (grub_uint32_t window,
+ * 						 grub_uint32_t *position);
+ *
+ * Register allocations for parameters:
+ * %eax		window
+ * %edx		*position
+ */
+FUNCTION(grub_vbe_get_memory_window)
+	pushl   %ebp
+	pushl   %ebx
+	pushl	%edx			/* push *position to stack */
+
+	movl	%eax, %ebx		/* store window in ebx */
+
+	call    prot_to_real
+	.code16
+
+	movw    $0x4f05, %ax
+	andw	$0x00ff, %bx		/* BL = window */
+	orw	$0x0100, %bx		/* BH = 1, Get memory window */
+	int     $0x10
+
+	movw	%ax, %bx		/* real_to_prot destroys %eax */
+
+	DATA32 call     real_to_prot
+	.code32
+
+	popl	%edi			/* pops *position from stack to %edi */
+	andl	$0xFFFF, %edx
+	movl	%edx, (%edi)		/* return position to caller */
+
+	movw	%bx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl    %ebx
+	popl    %ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_set_scanline_length (grub_uint32_t length)
+ *
+ * Register allocations for parameters:
+ * %eax		length
+ */
+FUNCTION(grub_vbe_set_scanline_length)
+	pushl	%ebp
+	pushl	%ebx
+
+	movl	%eax, %ecx		/* store length in ecx */
+
+	call	prot_to_real
+	.code16
+
+	movw	$0x4f06, %ax
+	movw	$0x0002, %bx		/* BL = 2, Set Scan Line in Bytes */
+	int	$0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	DATA32 call	real_to_prot
+	.code32
+	
+	movw	%dx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl	%ebx
+	popl	%ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_get_scanline_length (grub_uint32_t *length)
+ *
+ * Register allocations for parameters:
+ * %eax		*length
+ */
+FUNCTION(grub_vbe_get_scanline_length)
+	pushl   %ebp
+	pushl   %ebx
+	pushl	%edx			/* push *length to stack */
+
+	call    prot_to_real
+	.code16
+
+	movw    $0x4f06, %ax
+	movw	$0x0001, %bx		/* BL = 1, Get Scan Line Length (in bytes) */
+	int     $0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	DATA32 call     real_to_prot
+	.code32
+
+	popl	%edi			/* pops *length from stack to %edi */
+	andl	$0xFFFF, %ebx
+	movl	%ebx, (%edi)		/* return length to caller */
+
+	movw	%dx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl    %ebx
+	popl    %ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_set_display_start (grub_uint32_t x,
+ *						 grub_uint32_t y)
+ *
+ * Register allocations for parameters:
+ * %eax		x
+ * %edx		y
+ */
+FUNCTION(grub_vbe_set_display_start)
+	pushl	%ebp
+	pushl	%ebx
+
+	movl	%eax, %ecx		/* store x in ecx */
+
+	call	prot_to_real
+	.code16
+
+	movw	$0x4f07, %ax
+	movw	$0x0080, %bx		/* BL = 80h, Set Display Start during Vertical Retrace */
+	int	$0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	DATA32 call	real_to_prot
+	.code32
+	
+	movw	%dx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl	%ebx
+	popl	%ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_get_display_start (grub_uint32_t *x,
+ *						 grub_uint32_t *y)
+ *
+ * Register allocations for parameters:
+ * %eax		*x
+ * %edx		*y
+ */
+FUNCTION(grub_vbe_get_display_start)
+	pushl   %ebp
+	pushl   %ebx
+	pushl	%eax			/* push *x to stack */
+	pushl	%edx			/* push *y to stack */
+
+	call    prot_to_real
+	.code16
+
+	movw    $0x4f07, %ax
+	movw	$0x0001, %bx		/* BL = 1, Get Display Start */
+	int     $0x10
+
+	movw	%ax, %bx		/* real_to_prot destroys %eax */
+
+	DATA32 call     real_to_prot
+	.code32
+
+	popl	%edi			/* pops *y from stack to %edi */
+	andl	$0xFFFF, %edx
+	movl	%edx, (%edi)		/* return y-position to caller */
+
+	popl	%edi			/* pops *x from stack to %edi */
+	andl	$0xFFFF, %ecx
+	movl	%ecx, (%edi)		/* return x-position to caller */
+
+	movw	%bx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl    %ebx
+	popl    %ebp
+	ret
+
+/*
+ * grub_vbe_status_t grub_vbe_set_palette_data (grub_uint32_t color_count,
+ *						grub_uint32_t start_index,
+ *						struct grub_vbe_palette_data *palette_data)
+ *
+ * Register allocations for parameters:
+ * %eax		color_count
+ * %edx		start_index
+ * %ecx		*palette_data
+ */
+FUNCTION(grub_vbe_set_palette_data)
+	pushl	%ebp
+	pushl	%ebx
+
+	movl	%eax, %ebx		/* store color_count in ebx */
+
+	movw    %cx, %di		/* store *palette_data to ecx:di */
+	xorw    %cx, %cx
+	shrl    $4, %ecx
+
+	call    prot_to_real
+	.code16
+
+	pushw   %es
+
+	movw    %cx, %es		/* *palette_data is now on es:di */
+	movw	%bx, %cx		/* color_count is now on cx */
+
+	movw	$0x4f09, %ax
+	xorw	%bx, %bx		/* BL = 0, Set Palette Data */
+	int	$0x10
+
+	movw	%ax, %dx		/* real_to_prot destroys %eax */
+
+	popw	%es
+
+	DATA32 call	real_to_prot
+	.code32
+	
+	movw	%dx, %ax
+	andl	$0xFFFF, %eax		/* return value in %eax */
+
+	popl	%ebx
+	popl	%ebp
+	ret