gpiolib: check the 'ngpios' property in core gpiolib code

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>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index bc5ba52..535eb1b 100644 (file)
--- 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
@@ -646,6 +647,26 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
                goto err_free_dev_name;
        }
 
+       /*
+        * Try the device properties if the driver didn't supply the number
+        * of GPIO lines.
+        */
+       if (gc->ngpio == 0) {
+               ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
+               if (ret == -ENODATA)
+                       /*
+                        * -ENODATA means that there is no property found and
+                        * we want to issue the error message to the user.
+                        * Besides that, we want to return different error code
+                        * to state that supplied value is not valid.
+                        */
+                       ngpios = 0;
+               else if (ret)
+                       goto err_free_descs;
+
+               gc->ngpio = ngpios;
+       }
+
        if (gc->ngpio == 0) {
                chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
                ret = -EINVAL;