[PATCH] gpiolib: Check gc->get_direction() before calling gpiod_get_direction()

According to 'struct gpio_chip' documentation in linux/gpio/driver.h,
implementing .get_direction() is recommended but not mandatory.
Most places verify that gc->get_direction() exists before calling
gpiod_get_direction(), but gpiolib_dbg_show() doesn't.

Until commit 471e998c0e31 ("gpiolib: remove redundant callback check")
it was also verified by gpiod_get_direction() itself so calling it at
all time from gpiolib_dbg_show() was not an issue. But after the check
in gpiod_get_direction() has been removed, calling it inconditionaly
leads to a big fat warning in gpiochip_get_direction().

In gpiod_get_direction(), verify that gc->get_direction() exists
before calling gpiod_get_direction().

Fixes: 471e998c0e31 ("gpiolib: remove redundant callback check")
Signed-off-by: Christophe Leroy (CS GROUP) <[email protected]>
---
 drivers/gpio/gpiolib.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e5fb60111151..6abf73bf056a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -5417,7 +5417,8 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *gc)
 		flags = READ_ONCE(desc->flags);
 		is_irq = test_bit(GPIOD_FLAG_USED_AS_IRQ, &flags);
 		if (is_irq || test_bit(GPIOD_FLAG_REQUESTED, &flags)) {
-			gpiod_get_direction(desc);
+			if (gc->get_direction)
+				gpiod_get_direction(desc);
 			is_out = test_bit(GPIOD_FLAG_IS_OUT, &flags);
 			value = gpio_chip_get_value(gc, desc);
 			active_low = test_bit(GPIOD_FLAG_ACTIVE_LOW, &flags);
-- 
2.54.0