gpio: Support for unified device properties interface

Some drivers need to deal with only firmware representation of its
GPIOs. An example would be a GPIO button array driver where each button
is described as a separate firmware node in device tree. Typically these
child nodes do not have physical representation in the Linux device
model.

In order to help device drivers to handle such firmware child nodes we
add dev[m]_get_named_gpiod_from_child() that takes a child firmware
node pointer as its second argument (the first one is the parent device
itself), finds the GPIO using whatever is the underlying firmware
method, and requests the GPIO properly.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/gpio/devres.c b/drivers/gpio/devres.c
index 954b9f6b0ef82eb74437e0efce4781b53ba58e0f..13dbd3dfc33a03f833db9e3ad1a5a57d64781cdc 100644 (file)
--- a/drivers/gpio/devres.c
+++ b/drivers/gpio/devres.c
@@ -108,6 +108,38 @@ struct gpio_desc *__must_check __devm_gpiod_get_index(struct device *dev,
 }
 EXPORT_SYMBOL(__devm_gpiod_get_index);
 
+/**
+ * devm_get_gpiod_from_child - get a GPIO descriptor from a device's child node
+ * @dev:       GPIO consumer
+ * @child:     firmware node (child of @dev)
+ *
+ * GPIO descriptors returned from this function are automatically disposed on
+ * driver detach.
+ */
+struct gpio_desc *devm_get_gpiod_from_child(struct device *dev,
+                                           struct fwnode_handle *child)
+{
+       struct gpio_desc **dr;
+       struct gpio_desc *desc;
+
+       dr = devres_alloc(devm_gpiod_release, sizeof(struct gpio_desc *),
+                         GFP_KERNEL);
+       if (!dr)
+               return ERR_PTR(-ENOMEM);
+
+       desc = fwnode_get_named_gpiod(child, "gpios");
+       if (IS_ERR(desc)) {
+               devres_free(dr);
+               return desc;
+       }
+
+       *dr = desc;
+       devres_add(dev, dr);
+
+       return desc;
+}
+EXPORT_SYMBOL(devm_get_gpiod_from_child);
+
 /**
  * devm_gpiod_get_index_optional - Resource-managed gpiod_get_index_optional()
  * @dev: GPIO consumer

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 2bca0495cb460a580ab0cf23c8c8314465a17768..58659dbe702a86d7fded87d3c4cbaea7f5cbd945 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1734,6 +1734,61 @@ struct gpio_desc *__must_check __gpiod_get_index(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(__gpiod_get_index);
 
+/**
+ * fwnode_get_named_gpiod - obtain a GPIO from firmware node
+ * @fwnode:    handle of the firmware node
+ * @propname:  name of the firmware property representing the GPIO
+ *
+ * This function can be used for drivers that get their configuration
+ * from firmware.
+ *
+ * Function properly finds the corresponding GPIO using whatever is the
+ * underlying firmware interface and then makes sure that the GPIO
+ * descriptor is requested before it is returned to the caller.
+ *
+ * In case of error an ERR_PTR() is returned.
+ */
+struct gpio_desc *fwnode_get_named_gpiod(struct fwnode_handle *fwnode,
+                                        const char *propname)
+{
+       struct gpio_desc *desc = ERR_PTR(-ENODEV);
+       bool active_low = false;
+       int ret;
+
+       if (!fwnode)
+               return ERR_PTR(-EINVAL);
+
+       if (is_of_node(fwnode)) {
+               enum of_gpio_flags flags;
+
+               desc = of_get_named_gpiod_flags(of_node(fwnode), propname, 0,
+                                               &flags);
+               if (!IS_ERR(desc))
+                       active_low = flags & OF_GPIO_ACTIVE_LOW;
+       } else if (is_acpi_node(fwnode)) {
+               struct acpi_gpio_info info;
+
+               desc = acpi_get_gpiod_by_index(acpi_node(fwnode), propname, 0,
+                                              &info);
+               if (!IS_ERR(desc))
+                       active_low = info.active_low;
+       }
+
+       if (IS_ERR(desc))
+               return desc;
+
+       ret = gpiod_request(desc, NULL);
+       if (ret)
+               return ERR_PTR(ret);
+
+       /* Only value flag can be set from both DT and ACPI is active_low */
+       if (active_low)
+               set_bit(FLAG_ACTIVE_LOW, &desc->flags);
+
+       return desc;
+}
+EXPORT_SYMBOL_GPL(fwnode_get_named_gpiod);
+
 /**
  * gpiod_get_index_optional - obtain an optional GPIO from a multi-index GPIO
  *                            function

diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 12f146fa660434731df9ed2d8c2f6929dcc46217..00b1b70d68ba9fffd417142426c88a040d6320eb 100644 (file)
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -94,6 +94,13 @@ int gpiod_to_irq(const struct gpio_desc *desc);
 struct gpio_desc *gpio_to_desc(unsigned gpio);
 int desc_to_gpio(const struct gpio_desc *desc);
 
+/* Child properties interface */
+struct fwnode_handle;
+
+struct gpio_desc *fwnode_get_named_gpiod(struct fwnode_handle *fwnode,
+                                        const char *propname);
+struct gpio_desc *devm_get_gpiod_from_child(struct device *dev,
+                                           struct fwnode_handle *child);
 #else /* CONFIG_GPIOLIB */
 
 static inline struct gpio_desc *__must_check __gpiod_get(struct device *dev,