[PATCH v3 2/2] gpiolib: check the 'ngpios' property in core gpiolib code

[Bartosz Golaszewski <brgl@bgdev.pl>]

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@bgdev.pl>
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
v1 -> v2:
- use device_property_read_u32() instead of fwnode_property_read_u32()
- reverse the error check logic

v2 -> v3:
- don't shadow errors other than -ENODATA in device_property_read_u32()

 drivers/gpio/gpiolib.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index ede8b8a7aa18..f79fd2551cf7 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -599,6 +599,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	int base = gc->base;
 	unsigned int i;
 	int ret = 0;
+	u32 ngpios;
 
 	/*
 	 * First: allocate and populate the internal stat container, and
@@ -647,9 +648,17 @@ 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 = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
+		if (ret) {
+			if (ret == -ENODATA) {
+				chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
+				ret = -EINVAL;
+			}
+
+			goto err_free_descs;
+		}
+
+		gc->ngpio = ngpios;
 	}
 
 	if (gc->ngpio > FASTPATH_NGPIO)
-- 
2.25.1