- 根目录:
- drivers
- acpi
- acpica
- utmath.c
/*******************************************************************************
*
* Module Name: utmath - Integer math support routines
*
******************************************************************************/
/*
* Copyright (C) 2000 - 2014, Intel Corp.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions, and the following disclaimer,
* without modification.
* 2. Redistributions in binary form must reproduce at minimum a disclaimer
* substantially similar to the "NO WARRANTY" disclaimer below
* ("Disclaimer") and any redistribution must be conditioned upon
* including a substantially similar Disclaimer requirement for further
* binary redistribution.
* 3. Neither the names of the above-listed copyright holders nor the names
* of any contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* Alternatively, this software may be distributed under the terms of the
* GNU General Public License ("GPL") version 2 as published by the Free
* Software Foundation.
*
* NO WARRANTY
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGES.
*/
#include <acpi/acpi.h>
#include "accommon.h"
#define _COMPONENT ACPI_UTILITIES
ACPI_MODULE_NAME("utmath")
/*
* Optional support for 64-bit double-precision integer divide. This code
* is configurable and is implemented in order to support 32-bit kernel
* environments where a 64-bit double-precision math library is not available.
*
* Support for a more normal 64-bit divide/modulo (with check for a divide-
* by-zero) appears after this optional section of code.
*/
#ifndef ACPI_USE_NATIVE_DIVIDE
/* Structures used only for 64-bit divide */
typedef struct uint64_struct {
u32 lo;
u32 hi;
} uint64_struct;
typedef union uint64_overlay {
u64 full;
struct uint64_struct part;
} uint64_overlay;
/*******************************************************************************
*
* FUNCTION: acpi_ut_short_divide
*
* PARAMETERS: dividend - 64-bit dividend
* divisor - 32-bit divisor
* out_quotient - Pointer to where the quotient is returned
* out_remainder - Pointer to where the remainder is returned
*
* RETURN: Status (Checks for divide-by-zero)
*
* DESCRIPTION: Perform a short (maximum 64 bits divided by 32 bits)
* divide and modulo. The result is a 64-bit quotient and a
* 32-bit remainder.
*
******************************************************************************/
acpi_status
acpi_ut_short_divide(u64 dividend,
u32 divisor, u64 *out_quotient, u32 *out_remainder)
{
union uint64_overlay dividend_ovl;
union uint64_overlay quotient;
u32 remainder32;
ACPI_FUNCTION_TRACE(ut_short_divide);
/* Always check for a zero divisor */
if (divisor == 0) {
ACPI_ERROR((AE_INFO, "Divide by zero"));
return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
}
dividend_ovl.full = dividend;
/*
* The quotient is 64 bits, the remainder is always 32 bits,
* and is generated by the second divide.
*/
ACPI_DIV_64_BY_32(0, dividend_ovl.part.hi, divisor,
quotient.part.hi, remainder32);
ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor,
quotient.part.lo, remainder32);
/* Return only what was requested */
if (out_quotient) {
*out_quotient = quotient.full;
}
if (out_remainder) {
*out_remainder = remainder32;
}
return_ACPI_STATUS(AE_OK);
}
/*******************************************************************************
*
* FUNCTION: acpi_ut_divide
*
* PARAMETERS: in_dividend - Dividend
* in_divisor - Divisor
* out_quotient - Pointer to where the quotient is returned
* out_remainder - Pointer to where the remainder is returned
*
* RETURN: Status (Checks for divide-by-zero)
*
* DESCRIPTION: Perform a divide and modulo.
*
******************************************************************************/
acpi_status
acpi_ut_divide(u64 in_dividend,
u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
{
union uint64_overlay dividend;
union uint64_overlay divisor;
union uint64_overlay quotient;
union uint64_overlay remainder;
union uint64_overlay normalized_dividend;
union uint64_overlay normalized_divisor;
u32 partial1;
union uint64_overlay partial2;
union uint64_overlay partial3;
ACPI_FUNCTION_TRACE(ut_divide);
/* Always check for a zero divisor */
if (in_divisor == 0) {
ACPI_ERROR((AE_INFO, "Divide by zero"));
return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
}
divisor.full = in_divisor;
dividend.full = in_dividend;
if (divisor.part.hi == 0) {
/*
* 1) Simplest case is where the divisor is 32 bits, we can
* just do two divides
*/
remainder.part.hi = 0;
/*
* The quotient is 64 bits, the remainder is always 32 bits,
* and is generated by the second divide.
*/
ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo,
quotient.part.hi, partial1);
ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo,
quotient.part.lo, remainder.part.lo);
}
else {
/*
* 2) The general case where the divisor is a full 64 bits
* is more difficult
*/
quotient.part.hi = 0;
normalized_dividend = dividend;
normalized_divisor = divisor;
/* Normalize the operands (shift until the divisor is < 32 bits) */
do {
ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi,
normalized_divisor.part.lo);
ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi,
normalized_dividend.part.lo);
} while (normalized_divisor.part.hi != 0);
/* Partial divide */
ACPI_DIV_64_BY_32(normalized_dividend.part.hi,
normalized_dividend.part.lo,
normalized_divisor.part.lo,
quotient.part.lo, partial1);
/*
* The quotient is always 32 bits, and simply requires adjustment.
* The 64-bit remainder must be generated.
*/
partial1 = quotient.part.lo * divisor.part.hi;
partial2.full = (u64) quotient.part.lo * divisor.part.lo;
partial3.full = (u64) partial2.part.hi + partial1;
remainder.part.hi = partial3.part.lo;
remainder.part.lo = partial2.part.lo;
if (partial3.part.hi == 0) {
if (partial3.part.lo >= dividend.part.hi) {
if (partial3.part.lo == dividend.part.hi) {
if (partial2.part.lo > dividend.part.lo) {
quotient.part.lo--;
remainder.full -= divisor.full;
}
} else {
quotient.part.lo--;
remainder.full -= divisor.full;
}
}
remainder.full = remainder.full - dividend.full;
remainder.part.hi = (u32) - ((s32) remainder.part.hi);
remainder.part.lo = (u32) - ((s32) remainder.part.lo);
if (remainder.part.lo) {
remainder.part.hi--;
}
}
}
/* Return only what was requested */
if (out_quotient) {
*out_quotient = quotient.full;
}
if (out_remainder) {
*out_remainder = remainder.full;
}
return_ACPI_STATUS(AE_OK);
}
#else
/*******************************************************************************
*
* FUNCTION: acpi_ut_short_divide, acpi_ut_divide
*
* PARAMETERS: See function headers above
*
* DESCRIPTION: Native versions of the ut_divide functions. Use these if either
* 1) The target is a 64-bit platform and therefore 64-bit
* integer math is supported directly by the machine.
* 2) The target is a 32-bit or 16-bit platform, and the
* double-precision integer math library is available to
* perform the divide.
*
******************************************************************************/
acpi_status
acpi_ut_short_divide(u64 in_dividend,
u32 divisor, u64 *out_quotient, u32 *out_remainder)
{
ACPI_FUNCTION_TRACE(ut_short_divide);
/* Always check for a zero divisor */
if (divisor == 0) {
ACPI_ERROR((AE_INFO, "Divide by zero"));
return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
}
/* Return only what was requested */
if (out_quotient) {
*out_quotient = in_dividend / divisor;
}
if (out_remainder) {
*out_remainder = (u32) (in_dividend % divisor);
}
return_ACPI_STATUS(AE_OK);
}
acpi_status
acpi_ut_divide(u64 in_dividend,
u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
{
ACPI_FUNCTION_TRACE(ut_divide);
/* Always check for a zero divisor */
if (in_divisor == 0) {
ACPI_ERROR((AE_INFO, "Divide by zero"));
return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
}
/* Return only what was requested */
if (out_quotient) {
*out_quotient = in_dividend / in_divisor;
}
if (out_remainder) {
*out_remainder = in_dividend % in_divisor;
}
return_ACPI_STATUS(AE_OK);
}
#endif