[RFC PATCH 1/5] gpio: generic: add a generic register wrapper for MMIO and PMIO

[Jose Javier Rodriguez Barbarin <dev-josejavier.rodriguez@duagon.com>]

For adding support to port-mapped devices within gpio_generic_chip, a new
data type is required for passing to read_reg() and write_reg()
callbacks as I/O port-mapped and memory-mapped registers use different
data types.

Introduce a new struct gpio_chip_reg to encapsulate mmio addresses and
I/O port numbers.

Signed-off-by: Jose Javier Rodriguez Barbarin <dev-josejavier.rodriguez@duagon.com>
---
 include/linux/gpio/generic.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/linux/gpio/generic.h b/include/linux/gpio/generic.h
index ff566dc9c3cb..87c624070901 100644
--- a/include/linux/gpio/generic.h
+++ b/include/linux/gpio/generic.h
@@ -18,6 +18,7 @@ struct device;
 #define GPIO_GENERIC_NO_SET_ON_INPUT		BIT(6)
 #define GPIO_GENERIC_PINCTRL_BACKEND		BIT(7) /* Call pinctrl direction setters */
 #define GPIO_GENERIC_NO_INPUT			BIT(8) /* only output */
+#define GPIO_GENERIC_PORT_MAPPED		BIT(9) /* port-mapped */
 
 /**
  * struct gpio_generic_chip_config - Generic GPIO chip configuration data
@@ -56,6 +57,19 @@ struct gpio_generic_chip_config {
 	unsigned long flags;
 };
 
+/**
+ * struct gpio_chip_reg - Generic GPIO chip register descriptor for MMIO or port-mapped I/O
+ * @mmio: MMIO register address.
+ * @port: I/O Port register address.
+ *
+ * Describes a GPIO chip register located either in MMIO space or in
+ * port-mapped I/O space.
+ */
+struct gpio_chip_reg {
+	void __iomem *mmio;
+	unsigned long port;
+};
+
 /**
  * struct gpio_generic_chip - Generic GPIO chip implementation.
  * @gc: The underlying struct gpio_chip object, implementing low-level GPIO
-- 
2.53.0