[PATCH RFC 2/2] gpiolib: check the 'ngpios' property in core gpiolib code

[Bartosz Golaszewski <brgl@xxxxxxxx>]

Several drivers read the 'ngpios' device property on their own, but
since it's defined as a standard GPIO property in the device tree bindings
anyway, it's a good candidate for generalization. If the driver didn't
set its gc->ngpio, try to read the 'ngpios' property from the GPIO
device's firmware node before bailing out.

Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
 drivers/gpio/gpiolib.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 4c34c96ef136..23b0478163d4 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -598,6 +598,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	struct gpio_device *gdev;
 	unsigned long flags;
 	unsigned int i;
+	u32 ngpios;
 
 	/*
 	 * First: allocate and populate the internal stat container, and
@@ -646,9 +647,15 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	}
 
 	if (gc->ngpio == 0) {
-		chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
-		ret = -EINVAL;
-		goto err_free_descs;
+		ret = fwnode_property_read_u32(gdev->dev.fwnode, "ngpios",
+					       &ngpios);
+		if (ret == 0) {
+			gc->ngpio = ngpios;
+		} else {
+			chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
+			ret = -EINVAL;
+			goto err_free_descs;
+		}
 	}
 
 	if (gc->ngpio > FASTPATH_NGPIO)
-- 
2.30.1