1 /* -*- linux-c -*- ------------------------------------------------------- *
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright 2007 rPath, Inc. - All Rights Reserved
6 * This file is part of the Linux kernel, and is made available under
7 * the terms of the GNU General Public License version 2.
9 * ----------------------------------------------------------------------- */
12 * arch/i386/boot/edd.c
14 * Get EDD BIOS disk information
18 #include <linux/edd.h>
20 #if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
32 * Read the MBR (first sector) from a specific device.
34 static int read_mbr(u8 devno, void *buf)
37 u16 ax, bx, cx, dx, si;
39 memset(&dapa, 0, sizeof dapa);
40 dapa.pkt_size = sizeof(dapa);
42 dapa.buf_off = (size_t)buf;
46 ax = 0x4200; /* Extended Read */
49 asm("pushfl; stc; int $0x13; setc %%al; popfl"
50 : "+a" (ax), "+S" (si), "+d" (dx)
52 : "ebx", "ecx", "edi", "memory");
57 ax = 0x0201; /* Legacy Read, one sector */
58 cx = 0x0001; /* Sector 0-0-1 */
61 asm("pushfl; stc; int $0x13; setc %%al; popfl"
62 : "+a" (ax), "+c" (cx), "+d" (dx), "+b" (bx)
63 : : "esi", "edi", "memory");
65 return -(u8)ax; /* 0 or -1 */
68 static u32 read_mbr_sig(u8 devno, struct edd_info *ei)
71 char *mbrbuf_ptr, *mbrbuf_end;
73 u32 buf_base, mbr_base;
76 sector_size = ei->params.bytes_per_sector;
78 sector_size = 512; /* Best available guess */
80 /* Produce a naturally aligned buffer on the heap */
81 buf_base = (ds() << 4) + (u32)&_end;
82 mbr_base = (buf_base+sector_size-1) & ~(sector_size-1);
83 mbrbuf_ptr = _end + (mbr_base-buf_base);
84 mbrbuf_end = mbrbuf_ptr + sector_size;
86 /* Make sure we actually have space on the heap... */
87 if (!(boot_params.hdr.loadflags & CAN_USE_HEAP))
89 if (mbrbuf_end > (char *)(size_t)boot_params.hdr.heap_end_ptr)
92 if (read_mbr(devno, mbrbuf_ptr))
95 mbrsig = *(u32 *)&mbrbuf_ptr[EDD_MBR_SIG_OFFSET];
99 static int get_edd_info(u8 devno, struct edd_info *ei)
101 u16 ax, bx, cx, dx, di;
103 memset(ei, 0, sizeof *ei);
105 /* Check Extensions Present */
110 asm("pushfl; stc; int $0x13; setc %%al; popfl"
111 : "+a" (ax), "+b" (bx), "=c" (cx), "+d" (dx)
115 return -1; /* No extended information */
121 ei->version = ax >> 8; /* EDD version number */
122 ei->interface_support = cx; /* EDD functionality subsets */
124 /* Extended Get Device Parameters */
126 ei->params.length = sizeof(ei->params);
129 asm("pushfl; int $0x13; popfl"
130 : "+a" (ax), "+d" (dx)
132 : "ebx", "ecx", "edi");
134 /* Get legacy CHS parameters */
136 /* Ralf Brown recommends setting ES:DI to 0:0 */
142 "pushfl; stc; int $0x13; setc %%al; popfl; "
144 : "+a" (ax), "=b" (bx), "=c" (cx), "+d" (dx), "+D" (di)
148 ei->legacy_max_cylinder = (cx >> 8) + ((cx & 0xc0) << 2);
149 ei->legacy_max_head = dx >> 8;
150 ei->legacy_sectors_per_track = cx & 0x3f;
162 struct edd_info ei, *edp;
164 if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {
165 if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip"))
167 else if (!strcmp(eddarg, "off"))
171 edp = (struct edd_info *)boot_params.eddbuf;
176 for (devno = 0x80; devno < 0x80+EDD_MBR_SIG_MAX; devno++) {
178 * Scan the BIOS-supported hard disks and query EDD
181 get_edd_info(devno, &ei);
183 if (boot_params.eddbuf_entries < EDDMAXNR) {
184 memcpy(edp, &ei, sizeof ei);
186 boot_params.eddbuf_entries++;
191 mbr_sig = read_mbr_sig(devno, &ei);
192 boot_params.edd_mbr_sig_buffer[devno-0x80] = mbr_sig;