1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Software Node helpers for the GPIO API
4 *
5 * Copyright 2022 Google LLC
6 */
7
8#define pr_fmt(fmt) "gpiolib: swnode: " fmt
9
10#include <linux/err.h>
11#include <linux/errno.h>
12#include <linux/export.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/printk.h>
16#include <linux/property.h>
17#include <linux/string.h>
18
19#include <linux/gpio/consumer.h>
20#include <linux/gpio/driver.h>
21
22#include "gpiolib.h"
23#include "gpiolib-swnode.h"
24
25#define GPIOLIB_SWNODE_UNDEFINED_NAME "swnode-gpio-undefined"
26
27static void swnode_format_propname(const char *con_id, char *propname,
28				   size_t max_size)
29{
30	/*
31	 * Note we do not need to try both -gpios and -gpio suffixes,
32	 * as, unlike OF and ACPI, we can fix software nodes to conform
33	 * to the proper binding.
34	 */
35	if (con_id)
36		snprintf(propname, max_size, "%s-gpios", con_id);
37	else
38		strscpy(propname, "gpios", max_size);
39}
40
41static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode)
42{
43	const struct software_node *gdev_node;
44	struct gpio_device *gdev;
45
46	gdev_node = to_software_node(fwnode);
47	if (!gdev_node || !gdev_node->name)
48		return ERR_PTR(-EINVAL);
49
50	/*
51	 * Check for a special node that identifies undefined GPIOs, this is
52	 * primarily used as a key for internal chip selects in SPI bindings.
53	 */
54	if (IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED) &&
55	    !strcmp(gdev_node->name, GPIOLIB_SWNODE_UNDEFINED_NAME))
56		return ERR_PTR(-ENOENT);
57
58	gdev = gpio_device_find_by_label(gdev_node->name);
59	return gdev ?: ERR_PTR(-EPROBE_DEFER);
60}
61
62struct gpio_desc *swnode_find_gpio(struct fwnode_handle *fwnode,
63				   const char *con_id, unsigned int idx,
64				   unsigned long *flags)
65{
66	const struct software_node *swnode;
67	struct fwnode_reference_args args;
68	struct gpio_desc *desc;
69	char propname[32]; /* 32 is max size of property name */
70	int error;
71
72	swnode = to_software_node(fwnode);
73	if (!swnode)
74		return ERR_PTR(-EINVAL);
75
76	swnode_format_propname(con_id, propname, sizeof(propname));
77
78	/*
79	 * We expect all swnode-described GPIOs have GPIO number and
80	 * polarity arguments, hence nargs is set to 2.
81	 */
82	error = fwnode_property_get_reference_args(fwnode, propname, NULL, 2, idx, &args);
83	if (error) {
84		pr_debug("%s: can't parse '%s' property of node '%pfwP[%d]'\n",
85			__func__, propname, fwnode, idx);
86		return ERR_PTR(error);
87	}
88
89	struct gpio_device *gdev __free(gpio_device_put) =
90					swnode_get_gpio_device(args.fwnode);
91	fwnode_handle_put(args.fwnode);
92	if (IS_ERR(gdev))
93		return ERR_CAST(gdev);
94
95	/*
96	 * FIXME: The GPIO device reference is put at return but the descriptor
97	 * is passed on. Find a proper solution.
98	 */
99	desc = gpio_device_get_desc(gdev, args.args[0]);
100	*flags = args.args[1]; /* We expect native GPIO flags */
101
102	pr_debug("%s: parsed '%s' property of node '%pfwP[%d]' - status (%d)\n",
103		 __func__, propname, fwnode, idx, PTR_ERR_OR_ZERO(desc));
104
105	return desc;
106}
107
108/**
109 * swnode_gpio_count - count the GPIOs associated with a device / function
110 * @fwnode:	firmware node of the GPIO consumer, can be %NULL for
111 *		system-global GPIOs
112 * @con_id:	function within the GPIO consumer
113 *
114 * Return:
115 * The number of GPIOs associated with a device / function or %-ENOENT,
116 * if no GPIO has been assigned to the requested function.
117 */
118int swnode_gpio_count(const struct fwnode_handle *fwnode, const char *con_id)
119{
120	struct fwnode_reference_args args;
121	char propname[32];
122	int count;
123
124	swnode_format_propname(con_id, propname, sizeof(propname));
125
126	/*
127	 * This is not very efficient, but GPIO lists usually have only
128	 * 1 or 2 entries.
129	 */
130	count = 0;
131	while (fwnode_property_get_reference_args(fwnode, propname, NULL, 0,
132						  count, &args) == 0) {
133		fwnode_handle_put(args.fwnode);
134		count++;
135	}
136
137	return count ?: -ENOENT;
138}
139
140#if IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED)
141/*
142 * A special node that identifies undefined GPIOs, this is primarily used as
143 * a key for internal chip selects in SPI bindings.
144 */
145const struct software_node swnode_gpio_undefined = {
146	.name = GPIOLIB_SWNODE_UNDEFINED_NAME,
147};
148EXPORT_SYMBOL_NS_GPL(swnode_gpio_undefined, GPIO_SWNODE);
149
150static int __init swnode_gpio_init(void)
151{
152	int ret;
153
154	ret = software_node_register(&swnode_gpio_undefined);
155	if (ret < 0)
156		pr_err("failed to register swnode: %d\n", ret);
157
158	return ret;
159}
160subsys_initcall(swnode_gpio_init);
161
162static void __exit swnode_gpio_cleanup(void)
163{
164	software_node_unregister(&swnode_gpio_undefined);
165}
166__exitcall(swnode_gpio_cleanup);
167#endif
168