[v4,1/3] irq/irq_sim: add a simple interrupt simulator framework

diff --git a/include/linux/irq_sim.h b/include/linux/irq_sim.h
new file mode 100644
index 000000000000..9ee1a4f8bd94
--- /dev/null
+++ b/include/linux/irq_sim.h
@@ -0,0 +1,44 @@ 
+/*
+ * Copyright (C) 2017 Bartosz Golaszewski <brgl@bgdev.pl>
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#ifndef _LINUX_IRQ_SIM_H
+#define _LINUX_IRQ_SIM_H
+
+#include <linux/irq_work.h>
+
+/*
+ * Provides a framework for allocating simulated interrupts which can be
+ * requested like normal irqs and enqueued from process context.
+ */
+
+struct irq_sim_work_ctx {
+	struct irq_work work;
+	int irq;
+};
+
+struct irq_sim_irq_ctx {
+	int irqnum;
+	bool enabled;
+};
+
+struct irq_sim {
+	struct irq_sim_work_ctx work_ctx;
+	int irq_base;
+	unsigned int irq_count;
+	struct irq_sim_irq_ctx *irqs;
+};
+
+int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs);
+void irq_sim_fini(struct irq_sim *sim);
+
+void irq_sim_fire(struct irq_sim *sim, unsigned int offset);
+
+int irq_sim_irqnum(struct irq_sim *sim, unsigned int offset);
+
+#endif /* _LINUX_IRQ_SIM_H */
diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index 27c4e774071c..1d06af787932 100644
--- a/kernel/irq/Kconfig
+++ b/kernel/irq/Kconfig
@@ -63,6 +63,11 @@  config GENERIC_IRQ_CHIP
 config IRQ_DOMAIN
 	bool
 
+# Support for simulated interrupts
+config IRQ_SIM
+	bool
+	select IRQ_WORK
+
 # Support for hierarchical irq domains
 config IRQ_DOMAIN_HIERARCHY
 	bool
diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
index e4aef7351f2b..1970cafe8f2a 100644
--- a/kernel/irq/Makefile
+++ b/kernel/irq/Makefile
@@ -4,6 +4,7 @@  obj-$(CONFIG_IRQ_TIMINGS) += timings.o
 obj-$(CONFIG_GENERIC_IRQ_CHIP) += generic-chip.o
 obj-$(CONFIG_GENERIC_IRQ_PROBE) += autoprobe.o
 obj-$(CONFIG_IRQ_DOMAIN) += irqdomain.o
+obj-$(CONFIG_IRQ_SIM) += irq_sim.o
 obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_GENERIC_PENDING_IRQ) += migration.o
 obj-$(CONFIG_GENERIC_IRQ_MIGRATION) += cpuhotplug.o
diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
new file mode 100644
index 000000000000..31a2c12a79ae
--- /dev/null
+++ b/kernel/irq/irq_sim.c
@@ -0,0 +1,121 @@ 
+/*
+ * Copyright (C) 2017 Bartosz Golaszewski <brgl@bgdev.pl>
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/irq_sim.h>
+#include <linux/irq.h>
+
+static void irq_sim_irqmask(struct irq_data *data)
+{
+	struct irq_sim_irq_ctx *irq_ctx = irq_data_get_irq_chip_data(data);
+
+	irq_ctx->enabled = false;
+}
+
+static void irq_sim_irqunmask(struct irq_data *data)
+{
+	struct irq_sim_irq_ctx *irq_ctx = irq_data_get_irq_chip_data(data);
+
+	irq_ctx->enabled = true;
+}
+
+static struct irq_chip irq_sim_irqchip = {
+	.name		= "irq_sim",
+	.irq_mask	= irq_sim_irqmask,
+	.irq_unmask	= irq_sim_irqunmask,
+};
+
+static void irq_sim_handle_irq(struct irq_work *work)
+{
+	struct irq_sim_work_ctx *work_ctx;
+
+	work_ctx = container_of(work, struct irq_sim_work_ctx, work);
+	handle_simple_irq(irq_to_desc(work_ctx->irq));
+}
+
+/**
+ * irq_sim_init - Initialize the interrupt simulator: allocate a range of
+ *                dummy interrupts.
+ *
+ * @sim:        The interrupt simulator object to initialize.
+ * @num_irqs:   Number of interrupts to allocate
+ *
+ * Returns 0 on success and a negative error number on failure.
+ */
+int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
+{
+	int i;
+
+	sim->irqs = kmalloc_array(num_irqs, sizeof(*sim->irqs), GFP_KERNEL);
+	if (!sim->irqs)
+		return -ENOMEM;
+
+	sim->irq_base = irq_alloc_descs(-1, 0, num_irqs, 0);
+	if (sim->irq_base < 0) {
+		kfree(sim->irqs);
+		return sim->irq_base;
+	}
+
+	for (i = 0; i < num_irqs; i++) {
+		sim->irqs[i].irqnum = sim->irq_base + i;
+		sim->irqs[i].enabled = false;
+		irq_set_chip(sim->irq_base + i, &irq_sim_irqchip);
+		irq_set_chip_data(sim->irq_base + i, &sim->irqs[i]);
+		irq_set_handler(sim->irq_base + i, &handle_simple_irq);
+		irq_modify_status(sim->irq_base + i,
+				  IRQ_NOREQUEST | IRQ_NOAUTOEN, IRQ_NOPROBE);
+	}
+
+	init_irq_work(&sim->work_ctx.work, irq_sim_handle_irq);
+	sim->irq_count = num_irqs;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(irq_sim_init);
+
+/**
+ * irq_sim_fini - Deinitialize the interrupt simulator: free the interrupt
+ *                descriptors and allocated memory.
+ *
+ * @sim:        The interrupt simulator to tear down.
+ */
+void irq_sim_fini(struct irq_sim *sim)
+{
+	irq_work_sync(&sim->work_ctx.work);
+	irq_free_descs(sim->irq_base, sim->irq_count);
+	kfree(sim->irqs);
+}
+EXPORT_SYMBOL_GPL(irq_sim_fini);
+
+/**
+ * irq_sim_fire - Enqueue an interrupt.
+ *
+ * @sim:        The interrupt simulator object.
+ * @offset:     Offset of the simulated interrupt which should be fired.
+ */
+void irq_sim_fire(struct irq_sim *sim, unsigned int offset)
+{
+	if (sim->irqs[offset].enabled) {
+		sim->work_ctx.irq = irq_sim_irqnum(sim, offset);
+		irq_work_queue(&sim->work_ctx.work);
+	}
+}
+EXPORT_SYMBOL_GPL(irq_sim_fire);
+
+/**
+ * irq_sim_irqnum - Get the allocated number of a dummy interrupt.
+ *
+ * @sim:        The interrupt simulator object.
+ * @offset:     Offset of the simulated interrupt for which to retrieve
+ *              the number.
+ */
+int irq_sim_irqnum(struct irq_sim *sim, unsigned int offset)
+{
+	return sim->irqs[offset].irqnum;
+}
+EXPORT_SYMBOL_GPL(irq_sim_irqnum);