linux-kernel - [PATCH] gpio: siox: indicate exclusive support of threaded IRQs

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Date:   Tue,  4 Aug 2020 11:16:03 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Thorsten Scherer <t.scherer@...elmann.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Ahmad Fatoum <a.fatoum@...gutronix.de>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] gpio: siox: indicate exclusive support of threaded IRQs

Generic GPIO consumers like gpio-keys use request_any_context_irq()
to request a threaded handler if irq_settings_is_nested_thread() ==
true or a hardirq handler otherwise.

Drivers using handle_nested_irq() must be sure that the nested
IRQs were requested with threaded handlers, because the IRQ
is handled by calling action->thread_fn().

The gpio-siox driver dispatches IRQs via handle_nested_irq,
but has irq_settings_is_nested_thread() == false.

Set gpio_irq_chip::threaded to remedy this.

Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
---
I am writing a driver similar to gpio-siox and I ran into a null pointer
dereference, because ->threaded wasn't set. I didn't test this on actual
SIOX hardware.

This patch doesn't fix the case were are driver explicitly calls
request_irq and is combined with a driver that does handle_nested_irq.

Is there a flag, such drivers should additionally set or should we
check action->thread_fn before calling it inside handle_nested_irq?
---
 drivers/gpio/gpio-siox.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpio/gpio-siox.c b/drivers/gpio/gpio-siox.c
index 26e1fe092304..f8c5e9fc4bac 100644
--- a/drivers/gpio/gpio-siox.c
+++ b/drivers/gpio/gpio-siox.c
@@ -245,6 +245,7 @@ static int gpio_siox_probe(struct siox_device *sdevice)
 	girq->chip = &ddata->ichip;
 	girq->default_type = IRQ_TYPE_NONE;
 	girq->handler = handle_level_irq;
+	girq->threaded = true;

 	ret = devm_gpiochip_add_data(dev, &ddata->gchip, NULL);
 	if (ret)
-- 
2.28.0