linux-kernel - [PATCH] gpiolib: Avoid side effects in gpio_is

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Date:   Fri, 12 May 2023 16:28:06 +1200
From:   Chris Packham <chris.packham@...iedtelesis.co.nz>
To:     linus.walleij@...aro.org, brgl@...ev.pl, johan@...nel.org,
        andy.shevchenko@...il.com, maz@...nel.org,
        Ben Brown <ben.brown@...iedtelesis.co.nz>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: [PATCH] gpiolib: Avoid side effects in gpio_is_visible()

Calling gpiod_to_irq() creates an irq_desc for the GPIO. This is not
something that should happen when just exporting the GPIO via sysfs. The
effect of this was observed as triggering a warning in
gpiochip_disable_irq() when kexec()ing after exporting a GPIO.

Remove the call to gpiod_to_irq() from gpio_is_visible(). The actual
intended creation of the irq_desc comes via edge_store() when requested
by the user.

Fixes: ebbeba120ab2 ("gpio: sysfs: fix gpio attribute-creation race")
Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
---

Notes:
    This is technically a v2 of
    https://lore.kernel.org/lkml/20230510001151.3946931-1-chris.packham@alliedtelesis.co.nz/
    but the solution is so different it's probably best to treat it as a new
    patch.

 drivers/gpio/gpiolib-sysfs.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 530dfd19d7b5..f859dcd1cbf3 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -362,8 +362,6 @@ static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
 		if (!show_direction)
 			mode = 0;
 	} else if (attr == &dev_attr_edge.attr) {
-		if (gpiod_to_irq(desc) < 0)
-			mode = 0;
 		if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
 			mode = 0;
 	}
-- 
2.40.1