1 files changed, 164 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c
new file mode 100644
index 000000000000..b44f35d68459
--- /dev/null
+++ b/drivers/gpio/gpiolib-swnode.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Software Node helpers for the GPIO API
+ *
+ * Copyright 2022 Google LLC
+ */
+
+#define pr_fmt(fmt) "gpiolib: swnode: " fmt
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/property.h>
+#include <linux/string.h>
+
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+
+#include "gpiolib.h"
+#include "gpiolib-swnode.h"
+
+#define GPIOLIB_SWNODE_UNDEFINED_NAME "swnode-gpio-undefined"
+
+static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode)
+{
+	const struct software_node *gdev_node;
+	struct gpio_device *gdev;
+
+	gdev_node = to_software_node(fwnode);
+	if (!gdev_node || !gdev_node->name)
+		goto fwnode_lookup;
+
+	/*
+	 * Check for a special node that identifies undefined GPIOs, this is
+	 * primarily used as a key for internal chip selects in SPI bindings.
+	 */
+	if (IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED) &&
+	    !strcmp(gdev_node->name, GPIOLIB_SWNODE_UNDEFINED_NAME))
+		return ERR_PTR(-ENOENT);
+
+fwnode_lookup:
+	gdev = gpio_device_find_by_fwnode(fwnode);
+	return gdev ?: ERR_PTR(-EPROBE_DEFER);
+}
+
+static int swnode_gpio_get_reference(const struct fwnode_handle *fwnode,
+				     const char *propname, unsigned int idx,
+				     struct fwnode_reference_args *args)
+{
+	/*
+	 * We expect all swnode-described GPIOs have GPIO number and
+	 * polarity arguments, hence nargs is set to 2.
+	 */
+	return fwnode_property_get_reference_args(fwnode, propname, NULL, 2, idx, args);
+}
+
+struct gpio_desc *swnode_find_gpio(struct fwnode_handle *fwnode,
+				   const char *con_id, unsigned int idx,
+				   unsigned long *flags)
+{
+	const struct software_node *swnode;
+	struct fwnode_reference_args args;
+	struct gpio_desc *desc;
+	char propname[32]; /* 32 is max size of property name */
+	int ret = 0;
+
+	swnode = to_software_node(fwnode);
+	if (!swnode)
+		return ERR_PTR(-EINVAL);
+
+	for_each_gpio_property_name(propname, con_id) {
+		ret = swnode_gpio_get_reference(fwnode, propname, idx, &args);
+		if (ret == 0)
+			break;
+	}
+	if (ret) {
+		pr_debug("%s: can't parse '%s' property of node '%pfwP[%d]'\n",
+			__func__, propname, fwnode, idx);
+		return ERR_PTR(ret);
+	}
+
+	struct gpio_device *gdev __free(gpio_device_put) =
+					swnode_get_gpio_device(args.fwnode);
+	fwnode_handle_put(args.fwnode);
+	if (IS_ERR(gdev))
+		return ERR_CAST(gdev);
+
+	/*
+	 * FIXME: The GPIO device reference is put at return but the descriptor
+	 * is passed on. Find a proper solution.
+	 */
+	desc = gpio_device_get_desc(gdev, args.args[0]);
+	*flags = args.args[1]; /* We expect native GPIO flags */
+
+	pr_debug("%s: parsed '%s' property of node '%pfwP[%d]' - status (%d)\n",
+		 __func__, propname, fwnode, idx, PTR_ERR_OR_ZERO(desc));
+
+	return desc;
+}
+
+/**
+ * swnode_gpio_count - count the GPIOs associated with a device / function
+ * @fwnode:	firmware node of the GPIO consumer, can be %NULL for
+ *		system-global GPIOs
+ * @con_id:	function within the GPIO consumer
+ *
+ * Returns:
+ * The number of GPIOs associated with a device / function or %-ENOENT,
+ * if no GPIO has been assigned to the requested function.
+ */
+int swnode_gpio_count(const struct fwnode_handle *fwnode, const char *con_id)
+{
+	struct fwnode_reference_args args;
+	char propname[32];
+	int count;
+
+	/*
+	 * This is not very efficient, but GPIO lists usually have only
+	 * 1 or 2 entries.
+	 */
+	for_each_gpio_property_name(propname, con_id) {
+		count = 0;
+		while (swnode_gpio_get_reference(fwnode, propname, count, &args) == 0) {
+			fwnode_handle_put(args.fwnode);
+			count++;
+		}
+		if (count)
+			return count;
+	}
+
+	return -ENOENT;
+}
+
+#if IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED)
+/*
+ * A special node that identifies undefined GPIOs, this is primarily used as
+ * a key for internal chip selects in SPI bindings.
+ */
+const struct software_node swnode_gpio_undefined = {
+	.name = GPIOLIB_SWNODE_UNDEFINED_NAME,
+};
+EXPORT_SYMBOL_NS_GPL(swnode_gpio_undefined, "GPIO_SWNODE");
+
+static int __init swnode_gpio_init(void)
+{
+	int ret;
+
+	ret = software_node_register(&swnode_gpio_undefined);
+	if (ret < 0)
+		pr_err("failed to register swnode: %d\n", ret);
+
+	return ret;
+}
+subsys_initcall(swnode_gpio_init);
+
+static void __exit swnode_gpio_cleanup(void)
+{
+	software_node_unregister(&swnode_gpio_undefined);
+}
+__exitcall(swnode_gpio_cleanup);
+#endif