[PATCH] gpiolib: acpi: Do not set the IRQ type if the IRQ is already in use

If the IRQ is already in use, then acpi_dev_gpio_irq_get_by() really
should not change the type underneath the current owner.

I specifically hit an issue with this an a Chuwi Hi8 Super (CWI509) Bay
Trail tablet, when the Boot OS selection in the BIOS is set to Android.
In this case _STA for a MAX17047 ACPI I2C device wrongly returns 0xf and
the _CRS resources for this device include a GpioInt pointing to a GPIO
already in use by an _AEI handler, with a different type then specified
in the _CRS for the MAX17047 device. Leading to the acpi_dev_gpio_irq_get()
call done by the i2c-core-acpi.c code changing the type breaking the
_AEI handler.

Now this clearly is a bug in the DSDT of this tablet (in Android mode),
but in general calling irq_set_irq_type() on an IRQ which already is
in use seems like a bad idea.

Signed-off-by: Hans de Goede <redacted>
---
 drivers/gpio/gpiolib-acpi.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index 985e8589c58b..24cd86bf2c4c 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c

@@ -1056,8 +1056,12 @@ int acpi_dev_gpio_irq_get_by(struct acpi_device *adev, const char *name, int ind
 			irq_flags = acpi_dev_get_irq_type(info.triggering,
 							  info.polarity);
 
-			/* Set type if specified and different than the current one */
-			if (irq_flags != IRQ_TYPE_NONE &&
+			/*
+			 * If the IRQ is not already in use then set type
+			 * if specified and different than the current one.
+			 */
+			if (can_request_irq(irq, irq_flags) &&
+			    irq_flags != IRQ_TYPE_NONE &&
 			    irq_flags != irq_get_trigger_type(irq))
 				irq_set_irq_type(irq, irq_flags);
 

-- 
2.33.1