From 6654e13fa3a98019c79f4cdb499e84f2295074e8 Mon Sep 17 00:00:00 2001
From: Bahadir Balban <bbalban@b-labs.co.uk>
Date: Mon, 30 Nov 2009 10:12:01 +0200
Subject: [PATCH] Added api/irq.c

---
 src/api/irq.c | 121 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 src/api/irq.c

diff --git a/src/api/irq.c b/src/api/irq.c
new file mode 100644
index 0000000..b00b417
--- /dev/null
+++ b/src/api/irq.c
@@ -0,0 +1,121 @@
+/*
+ * Userspace irq handling and management
+ *
+ * Copyright (C) 2009 Bahadir Balban
+ */
+#include <l4/api/irq.h>
+#include <l4/api/errno.h>
+#include <l4/generic/scheduler.h>
+#include <l4/generic/thread.h>
+#include <l4/generic/capability.h>
+#include <l4/generic/irq.h>
+#include <l4/generic/tcb.h>
+#include INC_GLUE(message.h)
+#include <l4/lib/wait.h>
+
+/*
+ * Default function that handles userspace
+ * threaded irqs. Increases notification count and wakes
+ * up any waiters.
+ *
+ * The increment is a standard read/update/write, and
+ * it is atomic due to multiple reasons:
+ *
+ * - We are atomic with regard to the task because we are
+ *   in irq context. Task cannot run during the period where
+ *   we read update and write the value.
+ *
+ * - The task does an atomic swap on reads, writing 0 to the
+ *   location in the same instruction as it reads it. As a
+ *   result task updates on the slot are atomic, and cannot
+ *   interfere with the read/update/write of the irq.
+ *
+ * - Recursive irqs are enabled, but we are also protected
+ *   from them because the current irq number is masked.
+ */
+int thread_notify_default(struct irq_desc *desc)
+{
+	struct utcb *utcb;
+	int err;
+
+	/* Make sure irq thread's utcb is mapped */
+	if ((err = tcb_check_and_lazy_map_utcb(desc->irq_thread,
+					       0)) < 0) {
+		printk("%s: Irq occured but registered task's utcb "
+		       "is inaccessible. task id=0x%x err=%d\n"
+		       "Destroying task.", __FUNCTION__,
+		       desc->irq_thread->tid, err);
+		thread_destroy(desc->irq_thread);
+		/* FIXME: Deregister and disable irq as well */
+	}
+
+	/* Get thread's utcb */
+	utcb = (struct utcb *)desc->irq_thread->utcb_address;
+
+	/* Atomic increment (See above comments) with no wraparound */
+	if (utcb->notify[desc->task_notify_slot] != TASK_NOTIFY_MAX)
+		utcb->notify[desc->task_notify_slot]++;
+
+	/*
+	 * Wake up any waiters
+	 *
+	 * NOTE: There's no contention on this queue, if there was,
+	 * we would have to have spin_lock_irq()'s on the wakeup
+	 */
+	wake_up(&desc->irq_thread->wqh_notify, WAKEUP_ASYNC);
+
+	return 0;
+}
+
+/*
+ * Register the given globally unique irq number with the
+ * current thread with given flags
+ */
+int irq_control_register(struct ktcb *task, int notify_slot, l4id_t irqnum)
+{
+	int err;
+
+	if (notify_slot >= TASK_NOTIFY_SLOTS)
+		return -EINVAL;
+
+	/*
+	 * Check that utcb memory accesses won't fault us.
+	 *
+	 * We make sure that the irq registrar has its utcb mapped,
+	 * so that if an irq occurs, the utcb address must be at
+	 * least readily available to be copied over to the page
+	 * tables of the task runnable at the time of the irq.
+	 */
+	if ((err = tcb_check_and_lazy_map_utcb(current, 1)) < 0)
+		return err;
+
+	/* Register the irq and thread notification handler */
+	if ((err = irq_register(current, notify_slot, irqnum,
+				thread_notify_default)) < 0)
+		return err;
+
+	return 0;
+}
+
+/*
+ * Register/deregister device irqs. Optional synchronous and
+ * asynchronous irq handling.
+ */
+int sys_irq_control(unsigned int req, int slot, unsigned int flags, l4id_t irqno)
+{
+	/* Currently a task is allowed to register only for itself */
+	struct ktcb *task = current;
+	int err;
+
+	if ((err = cap_irq_check(task, req, flags, irqno)) < 0)
+		return err;
+
+	switch (req) {
+	case IRQ_CONTROL_REGISTER:
+		irq_control_register(task, flags, irqno);
+	default:
+			return -EINVAL;
+	}
+	return 0;
+}
+