linux/drivers/gpio/gpiolib-swnode.c

// 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 <linux/gpio/property.h>

#include "gpiolib.h"
#include "gpiolib-swnode.h"

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)
		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) &&
	    gdev_node == &swnode_gpio_undefined)
		return ERR_PTR(-ENOENT);

fwnode_lookup:
	gdev = gpio_device_find_by_fwnode(fwnode);
	if (!gdev && gdev_node && gdev_node->name)
		/*
		 * FIXME: We shouldn't need to compare the GPIO controller's
		 * label against the software node that is supposedly attached
		 * to it. However there are currently GPIO users that - knowing
		 * the expected label of the GPIO chip whose pins they want to
		 * control - set up dummy software nodes named after those GPIO
		 * controllers, which aren't actually attached to them. In this
		 * case gpio_device_find_by_fwnode() will fail as no device on
		 * the GPIO bus is actually associated with the fwnode we're
		 * looking for.
		 *
		 * As a fallback: continue checking the label if we have no
		 * match. However, the situation described above is an abuse
		 * of the software node API and should be phased out and the
		 * following line - eventually removed.
		 */
		gdev = gpio_device_find_by_label(gdev_node->name);

	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 == -ENOTCONN)
			/*
			 * -ENOTCONN for a software node reference lookup means
			 *  that a remote struct software_node exists but has
			 *  not yet been registered as a firmware node. Defer
			 *  until this happens.
			 */
			return ERR_PTR(-EPROBE_DEFER);
	}
	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 = "swnode-gpio-undefined",
};
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