1 // SPDX-License-Identifier: GPL-2.0-only 2 /* -*- linux-c -*- ------------------------------------------------------- * 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 * Copyright 2007 rPath, Inc. - All Rights Reserved 6 * Copyright 2009 Intel Corporation; author H. Peter Anvin 7 * 8 * Original APM BIOS checking by Stephen Rothwell, May 1994 9 * (sfr@canb.auug.org.au) 10 * 11 * ----------------------------------------------------------------------- */ 12 13 /* 14 * Get APM BIOS information 15 */ 16 17 #include "boot.h" 18 19 int query_apm_bios(void) 20 { 21 struct biosregs ireg, oreg; 22 23 /* APM BIOS installation check */ 24 initregs(&ireg); 25 ireg.ah = 0x53; 26 intcall(0x15, &ireg, &oreg); 27 28 if (oreg.flags & X86_EFLAGS_CF) 29 return -1; /* No APM BIOS */ 30 31 if (oreg.bx != 0x504d) /* "PM" signature */ 32 return -1; 33 34 if (!(oreg.cx & 0x02)) /* 32 bits supported? */ 35 return -1; 36 37 /* Disconnect first, just in case */ 38 ireg.al = 0x04; 39 intcall(0x15, &ireg, NULL); 40 41 /* 32-bit connect */ 42 ireg.al = 0x03; 43 intcall(0x15, &ireg, &oreg); 44 45 boot_params.apm_bios_info.cseg = oreg.ax; 46 boot_params.apm_bios_info.offset = oreg.ebx; 47 boot_params.apm_bios_info.cseg_16 = oreg.cx; 48 boot_params.apm_bios_info.dseg = oreg.dx; 49 boot_params.apm_bios_info.cseg_len = oreg.si; 50 boot_params.apm_bios_info.cseg_16_len = oreg.hsi; 51 boot_params.apm_bios_info.dseg_len = oreg.di; 52 53 if (oreg.flags & X86_EFLAGS_CF) 54 return -1; 55 56 /* Redo the installation check as the 32-bit connect; 57 some BIOSes return different flags this way... */ 58 59 ireg.al = 0x00; 60 intcall(0x15, &ireg, &oreg); 61 62 if ((oreg.eflags & X86_EFLAGS_CF) || oreg.bx != 0x504d) { 63 /* Failure with 32-bit connect, try to disconect and ignore */ 64 ireg.al = 0x04; 65 intcall(0x15, &ireg, NULL); 66 return -1; 67 } 68 69 boot_params.apm_bios_info.version = oreg.ax; 70 boot_params.apm_bios_info.flags = oreg.cx; 71 return 0; 72 } 73 74