gpio: Add a function to obtain a GPIO vector value

We can use GPIOs as binary digits for reading 'strapping' values. Each GPIO
is assigned a single bit and can be set high or low on the circuit board. We
already have a legacy function for reading these values. Add one that
supports driver model.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

drivers/gpio/gpio-uclass.c

@@ -577,6 +577,24 @@ int gpio_get_values_as_int(const int *gpio_list)
 	return vector;
 }
 
+int dm_gpio_get_values_as_int(struct gpio_desc *desc_list, int count)
+{
+	unsigned bitmask = 1;
+	unsigned vector = 0;
+	int ret, i;
+
+	for (i = 0; i < count; i++) {
+		ret = dm_gpio_get_value(&desc_list[i]);
+		if (ret < 0)
+			return ret;
+		else if (ret)
+			vector |= bitmask;
+		bitmask <<= 1;
+	}
+
+	return vector;
+}
+
 static int _gpio_request_by_name_nodev(const void *blob, int node,
 				       const char *list_name, int index,
 				       struct gpio_desc *desc, int flags,

include/asm-generic/gpio.h

@@ -359,6 +359,18 @@ int gpio_lookup_name(const char *name, struct udevice **devp,
  */
 int gpio_get_values_as_int(const int *gpio_list);
 
+/**
+ * dm_gpio_get_values_as_int() - Turn the values of a list of GPIOs into an int
+ *
+ * This puts the value of the first GPIO into bit 0, the second into bit 1,
+ * etc. then returns the resulting integer.
+ *
+ * @desc_list: List of GPIOs to collect
+ * @count: Number of GPIOs
+ * @return resulting integer value, or -ve on error
+ */
+int dm_gpio_get_values_as_int(struct gpio_desc *desc_list, int count);
+
 /**
  * gpio_claim_vector() - claim a number of GPIOs for input
  *