EDD probing code for the new x86 setup code

/* -*- linux-c -*- ------------------------------------------------------- *

 *

 *   Copyright (C) 1991, 1992 Linus Torvalds

 *   Copyright 2007 rPath, Inc. - All Rights Reserved

 *

 *   This file is part of the Linux kernel, and is made available under

 *   the terms of the GNU General Public License version 2.

 *

 * ----------------------------------------------------------------------- */

/*

 * arch/i386/boot/edd.c

 *

 * Get EDD BIOS disk information

 */

#include "boot.h"

#include <linux/edd.h>

#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)

struct edd_dapa {

	u8	pkt_size;

	u8	rsvd;

	u16	sector_cnt;

	u16	buf_off, buf_seg;

	u64	lba;

	u64	buf_lin_addr;

};

/*

 * Read the MBR (first sector) from a specific device.

 */

static int read_mbr(u8 devno, void *buf)

{

	struct edd_dapa dapa;

	u16 ax, bx, cx, dx, si;

	memset(&dapa, 0, sizeof dapa);

	dapa.pkt_size = sizeof(dapa);

	dapa.sector_cnt = 1;

	dapa.buf_off = (size_t)buf;

	dapa.buf_seg = ds();

	/* dapa.lba = 0; */

	ax = 0x4200;		/* Extended Read */

	si = (size_t)&dapa;

	dx = devno;

	asm("pushfl; stc; int $0x13; setc %%al; popfl"

	    : "+a" (ax), "+S" (si), "+d" (dx)

	    : "m" (dapa)

	    : "ebx", "ecx", "edi", "memory");

	if (!(u8)ax)

		return 0;	/* OK */

	ax = 0x0201;		/* Legacy Read, one sector */

	cx = 0x0001;		/* Sector 0-0-1 */

	dx = devno;

	bx = (size_t)buf;

	asm("pushfl; stc; int $0x13; setc %%al; popfl"

	    : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx)

	    : : "esi", "edi", "memory");

	return -(u8)ax;		/* 0 or -1 */

}

static u32 read_mbr_sig(u8 devno, struct edd_info *ei)

{

	int sector_size;

	char *mbrbuf_ptr, *mbrbuf_end;

	u32 mbrsig;

	u32 buf_base, mbr_base;

	extern char _end[];

	static char mbr_buf[1024];

	sector_size = ei->params.bytes_per_sector;

	if (!sector_size)

		sector_size = 512; /* Best available guess */

	buf_base = (ds() << 4) + (u32)&_end;

	mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);

	mbrbuf_ptr = mbr_buf + (mbr_base-buf_base);

	mbrbuf_end = mbrbuf_ptr + sector_size;

	if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))

		return 0;

	if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)

		return 0;

	if (read_mbr(devno, mbrbuf_ptr))

		return 0;

	mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];

	return mbrsig;

}

static int get_edd_info(u8 devno, struct edd_info *ei)

{

	u16 ax, bx, cx, dx, di;

	memset(ei, 0, sizeof *ei);

	/* Check Extensions Present */

	ax = 0x4100;

	bx = EDDMAGIC1;

	dx = devno;

	asm("pushfl; stc; int $0x13; setc %%al; popfl"

	    : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx)

	    : : "esi", "edi");

	if ((u8)ax)

		return -1;	/* No extended information */

	if (bx != EDDMAGIC2)

		return -1;

	ei->device  = devno;

	ei->version = ax >> 8;	/* EDD version number */

	ei->interface_support = cx; /* EDD functionality subsets */

	/* Extended Get Device Parameters */

	ei->params.length = sizeof(ei->params);

	ax = 0x4800;

	dx = devno;

	asm("pushfl; int $0x13; popfl"

	    : "+a" (ax), "+d" (dx)

	    : "S" (&ei->params)

	    : "ebx", "ecx", "edi");

	/* Get legacy CHS parameters */

	/* Ralf Brown recommends setting ES:DI to 0:0 */

	ax = 0x0800;

	dx = devno;

	di = 0;

	asm("pushw %%es; "

	    "movw %%di,%%es; "

	    "pushfl; stc; int $0x13; setc %%al; popfl; "

	    "popw %%es"

	    : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di)

	    : : "esi");

	if ((u8)ax == 0) {

		ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2);

		ei->legacy_max_head = dx >> 8;

		ei->legacy_sectors_per_track = cx & 0x3f;

	}

	return 0;

}

void query_edd(void)

{

	char eddarg[8];

	int do_mbr = 1;

	int do_edd = 1;

	int devno;

	struct edd_info ei, *edp;

	if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {

		if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip"))

			do_mbr = 0;

		else if (!strcmp(eddarg, "off"))

			do_edd = 0;

	}

	edp = (struct edd_info *)boot_params.eddbuf;

	if (!do_edd)

		return;

	for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {

		/*

		 * Scan the BIOS-supported hard disks and query EDD

		 * information...

		 */

		get_edd_info(devno, &ei);

		if (boot_params.eddbuf_entries < EDDMAXNR) {

			memcpy(edp, &ei, sizeof ei);

			edp++;

			boot_params.eddbuf_entries++;

		}

		if (do_mbr) {

			u32 mbr_sig;

			mbr_sig = read_mbr_sig(devno, &ei);

			boot_params.edd_mbr_sig_buffer[devno-0x80] = mbr_sig;

		}

	}

}

#endif