From 321d86b46656a15e91c35d7b9c35cada93a66ef8 Mon Sep 17 00:00:00 2001
From: daniel-k <github@daniel-krebs.net>
Date: Mon, 29 Aug 2016 18:20:28 +0200
Subject: [PATCH] asm/irqflags: fix documentation and simplify

---
 hermit/arch/x86/include/asm/irqflags.h | 87 +++++++++++++-------------
 1 file changed, 44 insertions(+), 43 deletions(-)

diff --git a/hermit/arch/x86/include/asm/irqflags.h b/hermit/arch/x86/include/asm/irqflags.h
index 6a14ec63c..0cd60065b 100644
--- a/hermit/arch/x86/include/asm/irqflags.h
+++ b/hermit/arch/x86/include/asm/irqflags.h
@@ -41,54 +41,12 @@
 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 uint8_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(uint8_t flags) {
-	if (flags)
-		irq_enable();
-}
-
 /** @brief Determines, if the interrupt flags (IF) is set
  *
  * @return
  * - 1 interrupt flag is set
  * - 0 interrupt flag is cleared
- */ 
+ */
 inline static uint8_t is_irq_enabled(void)
 {
 	size_t flags;
@@ -98,6 +56,49 @@ inline static uint8_t is_irq_enabled(void)
 	return 0;
 }
 
+/** @brief Disable IRQs
+ *
+ * This inline function just clears out the interrupt bit
+ */
+inline static void irq_disable(void) {
+	asm volatile("cli" ::: "memory");
+}
+
+/** @brief Enable IRQs
+ *
+ * This inline function just sets the interrupt bit
+ */
+inline static void irq_enable(void) {
+	asm volatile("sti" ::: "memory");
+}
+
+/** @brief Disable IRQs (nested)
+ *
+ * Disable IRQs when unsure if IRQs were enabled at all.
+ * 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 Whether IRQs had been enabled or not before disabling
+ */
+inline static uint8_t irq_nested_disable(void) {
+	uint8_t was_enabled = is_irq_enabled();
+	irq_disable();
+	return was_enabled;
+}
+
+/** @brief Enable IRQs (nested)
+ *
+ * Can be used in conjunction with irq_nested_disable() to only enable
+ * interrupts again if they were enabled before.
+ *
+ * @param was_enabled Whether IRQs should be enabled or not
+ */
+inline static void irq_nested_enable(uint8_t was_enabled) {
+	if (was_enabled)
+		irq_enable();
+}
+
 #ifdef __cplusplus
 }
 #endif