linux-kernel - [PATCH] um: irq: don't set the chip for all irqs

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Message-Id: <20190314150344.8555-1-brgl@bgdev.pl>
Date:   Thu, 14 Mar 2019 16:03:44 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: [PATCH] um: irq: don't set the chip for all irqs

From: Bartosz Golaszewski <bgolaszewski@...libre.com>

Setting a chip for an interrupt marks it as allocated. Since UM doesn't
support dynamic interrupt numbers (yet), it means we cannot simply
increase NR_IRQS and then use the free irqs between LAST_IRQ and NR_IRQS
with gpio-mockup or iio testing drivers as irq_alloc_descs() will fail
after not being able to neither find an unallocated range of interrupts
nor expand the range.

Only call irq_set_chip_and_handler() for irqs until LAST_IRQ.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
---
Note: I plan to introduce support for SPARSE_IRQ but AFAICT it will be
a bit more complicated, so in the meantime I'd like to propose this change.

 arch/um/kernel/irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
index f4874b7ec503..598d7b3d9355 100644
--- a/arch/um/kernel/irq.c
+++ b/arch/um/kernel/irq.c
@@ -479,7 +479,7 @@ void __init init_IRQ(void)
 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
 
 
-	for (i = 1; i < NR_IRQS; i++)
+	for (i = 1; i < LAST_IRQ; i++)
 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
 	/* Initialize EPOLL Loop */
 	os_setup_epoll();
-- 
2.20.1