1 files changed, 123 insertions, 0 deletions
diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c
new file mode 100644
index 000000000000..dd9ccac214d1
--- /dev/null
+++ b/drivers/gpio/gpiolib-swnode.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Software Node helpers for the GPIO API
+ *
+ * Copyright 2022 Google LLC
+ */
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/property.h>
+#include <linux/string.h>
+
+#include "gpiolib.h"
+#include "gpiolib-swnode.h"
+
+static void swnode_format_propname(const char *con_id, char *propname,
+				   size_t max_size)
+{
+	/*
+	 * Note we do not need to try both -gpios and -gpio suffixes,
+	 * as, unlike OF and ACPI, we can fix software nodes to conform
+	 * to the proper binding.
+	 */
+	if (con_id)
+		snprintf(propname, max_size, "%s-gpios", con_id);
+	else
+		strscpy(propname, "gpios", max_size);
+}
+
+static int swnode_gpiochip_match_name(struct gpio_chip *chip, void *data)
+{
+	return !strcmp(chip->label, data);
+}
+
+static struct gpio_chip *swnode_get_chip(struct fwnode_handle *fwnode)
+{
+	const struct software_node *chip_node;
+	struct gpio_chip *chip;
+
+	chip_node = to_software_node(fwnode);
+	if (!chip_node || !chip_node->name)
+		return ERR_PTR(-EINVAL);
+
+	chip = gpiochip_find((void *)chip_node->name, swnode_gpiochip_match_name);
+	return chip ?: ERR_PTR(-EPROBE_DEFER);
+}
+
+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_chip *chip;
+	struct gpio_desc *desc;
+	char propname[32]; /* 32 is max size of property name */
+	int error;
+
+	swnode = to_software_node(fwnode);
+	if (!swnode)
+		return ERR_PTR(-EINVAL);
+
+	swnode_format_propname(con_id, propname, sizeof(propname));
+
+	/*
+	 * We expect all swnode-described GPIOs have GPIO number and
+	 * polarity arguments, hence nargs is set to 2.
+	 */
+	error = fwnode_property_get_reference_args(fwnode, propname, NULL, 2, idx, &args);
+	if (error) {
+		pr_debug("%s: can't parse '%s' property of node '%pfwP[%d]'\n",
+			__func__, propname, fwnode, idx);
+		return ERR_PTR(error);
+	}
+
+	chip = swnode_get_chip(args.fwnode);
+	fwnode_handle_put(args.fwnode);
+	if (IS_ERR(chip))
+		return ERR_CAST(chip);
+
+	desc = gpiochip_get_desc(chip, 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
+ *
+ * Return:
+ * 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;
+
+	swnode_format_propname(con_id, propname, sizeof(propname));
+
+	/*
+	 * This is not very efficient, but GPIO lists usually have only
+	 * 1 or 2 entries.
+	 */
+	count = 0;
+	while (fwnode_property_get_reference_args(fwnode, propname, NULL, 0,
+						  count, &args) == 0) {
+		fwnode_handle_put(args.fwnode);
+		count++;
+	}
+
+	return count ?: -ENOENT;
+}