/* 
 * Copyright 2010 Stefan Lankes, Chair for Operating Systems,
 *                               RWTH Aachen University
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file is part of MetalSVM.
 */

/**
 * @author Stefan Lankes
 * @file arch/x86/include/asm/irqflags.h
 * @brief Functions related to IRQ configuration
 *
 * This file contains definitions of inline functions 
 * for enabling and disabling IRQ handling.
 */

#ifndef __ARCH_IRQFLAGS_H__
#define __ARCH_IRQFLAGS_H__

#ifdef __cplusplus
extern "C" {
#endif

/** @brief Disable IRQs
 *
 * This inline function just clears out the interrupt bit
 */
inline static void irq_disable(void) {
	asm volatile("cli" ::: "memory");
}

/** @brief Disable IRQs (nested)
 *
 * Disable IRQs when unsure if IRQs were enabled at all.\n
 * This function together with irq_nested_enable can be used
 * in situations when interrupts shouldn't be activated if they
 * were not activated before calling this function.
 *
 * @return The set of flags which have been set until now
 */
inline static uint32_t irq_nested_disable(void) {
	size_t flags;
	asm volatile("pushf; cli; pop %0": "=r"(flags) : : "memory");
	if (flags & (1 << 9))
		return 1;	
	return 0;
}

/** @brief Enable IRQs */
inline static void irq_enable(void) {
	asm volatile("sti" ::: "memory");
}

/** @brief Enable IRQs (nested)
 *
 * If called after calling irq_nested_disable, this function will
 * not activate IRQs if they were not active before.
 *
 * @param flags Flags to set. Could be the old ones you got from irq_nested_disable.
 */
inline static void irq_nested_enable(uint32_t flags) {
	if (flags)
		irq_enable();
}

/** @brief Determines, if the interrupt flags (IF) is ser
 *
 * @return
 * - 1 interrupt flag is set
 * - 0 interrupt flag is cleared
 */ 
inline static uint32_t is_irq_enabled(void)
{
	size_t flags;
	asm volatile("pushf; pop %0": "=r"(flags) : : "memory");
	if (flags & (1 << 9))
		return 1;
	return 0;
}

#ifdef __cplusplus
}
#endif

#endif