[PATCH 1/2] genirq: Generic chip: add irq_unmap_generic_chip

[Sebastian Frias <sf84@laposte.net>]

Without this patch irq_domain_disassociate() cannot properly release the
interrupt.
Indeed, irq_map_generic_chip() checks a bit on 'gc->installed' but said bit
is never cleared, only set.

Commit 088f40b7b027 ("genirq: Generic chip: Add linear irq domain support")
added irq_map_generic_chip() function and also stated "This lacks a removal
function for now".

This commit provides with an implementation of an unmap function that can
be called by irq_domain_disassociate().

Fixes: 088f40b7b027 ("genirq: Generic chip: Add linear irq domain support")

Signed-off-by: Sebastian Frias <sf84@laposte.net>
---

This is required by loadable modules requesting IRQs.
In our case rmmod will perform free_irq() + irq_dispose_mapping().
Without the unmap call the module cannot request the IRQ after "rmmod"
because it is marked as "installed" by the first successful "insmod".

NOTE: While the proposed unmap() function attempts to undo as much things
as done by the map() function, I did not find a way to undo the following:

a) irq_gc_init_mask_cache(gc, dgc->gc_flags)
b) irq_set_lockdep_class(virq, &irq_nested_lock_class)
c) irq_modify_status(virq, dgc->irq_flags_to_clear, dgc->irq_flags_to_set)

Feel free to comment on that matter.

---
 kernel/irq/generic-chip.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/kernel/irq/generic-chip.c b/kernel/irq/generic-chip.c
index abd286a..7b464cd 100644
--- a/kernel/irq/generic-chip.c
+++ b/kernel/irq/generic-chip.c
@@ -411,8 +411,34 @@ int irq_map_generic_chip(struct irq_domain *d, unsigned int virq,
 }
 EXPORT_SYMBOL_GPL(irq_map_generic_chip);
 
+void irq_unmap_generic_chip(struct irq_domain *d, unsigned int virq)
+{
+	struct irq_data *data = irq_domain_get_irq_data(d, virq);
+	struct irq_domain_chip_generic *dgc = d->gc;
+	struct irq_chip_generic *gc;
+	unsigned int hw_irq = data->hwirq;
+	int chip_idx, irq_idx;
+
+	if (!d->gc)
+		return;
+
+	chip_idx = hw_irq / dgc->irqs_per_chip;
+	if (chip_idx >= dgc->num_chips)
+		return;
+	gc = dgc->gc[chip_idx];
+
+	irq_idx = hw_irq % dgc->irqs_per_chip;
+
+	clear_bit(irq_idx, &gc->installed);
+	irq_domain_set_info(d, virq, hw_irq,
+			    &no_irq_chip, NULL, NULL, NULL, NULL);
+
+}
+EXPORT_SYMBOL_GPL(irq_unmap_generic_chip);
+
 struct irq_domain_ops irq_generic_chip_ops = {
 	.map	= irq_map_generic_chip,
+	.unmap  = irq_unmap_generic_chip,
 	.xlate	= irq_domain_xlate_onetwocell,
 };
 EXPORT_SYMBOL_GPL(irq_generic_chip_ops);
-- 
1.7.11.2