drivers/gpio/gpiolib-swnode.c

   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
  27 static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode)
  28 {
  29         const struct software_node *gdev_node;
  30         struct gpio_device *gdev;
  31
  32         gdev_node = to_software_node(fwnode);
  33         if (!gdev_node || !gdev_node->name)
  34                 return ERR_PTR(-EINVAL);
  35
  36         /*
  37          * Check for a special node that identifies undefined GPIOs, this is
  38          * primarily used as a key for internal chip selects in SPI bindings.
  39          */
  40         if (IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED) &&
  41             !strcmp(gdev_node->name, GPIOLIB_SWNODE_UNDEFINED_NAME))
  42                 return ERR_PTR(-ENOENT);
  43
  44         gdev = gpio_device_find_by_label(gdev_node->name);
  45         return gdev ?: ERR_PTR(-EPROBE_DEFER);
  46 }
  47
  48 static int swnode_gpio_get_reference(const struct fwnode_handle *fwnode,
  49                                      const char *propname, unsigned int idx,
  50                                      struct fwnode_reference_args *args)
  51 {
  52         /*
  53          * We expect all swnode-described GPIOs have GPIO number and
  54          * polarity arguments, hence nargs is set to 2.
  55          */
  56         return fwnode_property_get_reference_args(fwnode, propname, NULL, 2, idx, args);
  57 }
  58
  59 struct gpio_desc *swnode_find_gpio(struct fwnode_handle *fwnode,
  60                                    const char *con_id, unsigned int idx,
  61                                    unsigned long *flags)
  62 {
  63         const struct software_node *swnode;
  64         struct fwnode_reference_args args;
  65         struct gpio_desc *desc;
  66         char propname[32]; /* 32 is max size of property name */
  67         int ret = 0;
  68
  69         swnode = to_software_node(fwnode);
  70         if (!swnode)
  71                 return ERR_PTR(-EINVAL);
  72
  73         for_each_gpio_property_name(propname, con_id) {
  74                 ret = swnode_gpio_get_reference(fwnode, propname, idx, &args);
  75                 if (ret == 0)
  76                         break;
  77         }
  78         if (ret) {
  79                 pr_debug("%s: can't parse '%s' property of node '%pfwP[%d]'\n",
  80                         __func__, propname, fwnode, idx);
  81                 return ERR_PTR(ret);
  82         }
  83
  84         struct gpio_device *gdev __free(gpio_device_put) =
  85                                         swnode_get_gpio_device(args.fwnode);
  86         fwnode_handle_put(args.fwnode);
  87         if (IS_ERR(gdev))
  88                 return ERR_CAST(gdev);
  89
  90         /*
  91          * FIXME: The GPIO device reference is put at return but the descriptor
  92          * is passed on. Find a proper solution.
  93          */
  94         desc = gpio_device_get_desc(gdev, args.args[0]);
  95         *flags = args.args[1]; /* We expect native GPIO flags */
  96
  97         pr_debug("%s: parsed '%s' property of node '%pfwP[%d]' - status (%d)\n",
  98                  __func__, propname, fwnode, idx, PTR_ERR_OR_ZERO(desc));
  99
 100         return desc;
 101 }
 102
 103 /**
 104  * swnode_gpio_count - count the GPIOs associated with a device / function
 105  * @fwnode:     firmware node of the GPIO consumer, can be %NULL for
 106  *              system-global GPIOs
 107  * @con_id:     function within the GPIO consumer
 108  *
 109  * Returns:
 110  * The number of GPIOs associated with a device / function or %-ENOENT,
 111  * if no GPIO has been assigned to the requested function.
 112  */
 113 int swnode_gpio_count(const struct fwnode_handle *fwnode, const char *con_id)
 114 {
 115         struct fwnode_reference_args args;
 116         char propname[32];
 117         int count;
 118
 119         /*
 120          * This is not very efficient, but GPIO lists usually have only
 121          * 1 or 2 entries.
 122          */
 123         for_each_gpio_property_name(propname, con_id) {
 124                 count = 0;
 125                 while (swnode_gpio_get_reference(fwnode, propname, count, &args) == 0) {
 126                         fwnode_handle_put(args.fwnode);
 127                         count++;
 128                 }
 129                 if (count)
 130                         return count;
 131         }
 132
 133         return -ENOENT;
 134 }
 135
 136 #if IS_ENABLED(CONFIG_GPIO_SWNODE_UNDEFINED)
 137 /*
 138  * A special node that identifies undefined GPIOs, this is primarily used as
 139  * a key for internal chip selects in SPI bindings.
 140  */
 141 const struct software_node swnode_gpio_undefined = {
 142         .name = GPIOLIB_SWNODE_UNDEFINED_NAME,
 143 };
 144 EXPORT_SYMBOL_NS_GPL(swnode_gpio_undefined, GPIO_SWNODE);
 145
 146 static int __init swnode_gpio_init(void)
 147 {
 148         int ret;
 149
 150         ret = software_node_register(&swnode_gpio_undefined);
 151         if (ret < 0)
 152                 pr_err("failed to register swnode: %d\n", ret);
 153
 154         return ret;
 155 }
 156 subsys_initcall(swnode_gpio_init);
 157
 158 static void __exit swnode_gpio_cleanup(void)
 159 {
 160         software_node_unregister(&swnode_gpio_undefined);
 161 }
 162 __exitcall(swnode_gpio_cleanup);
 163 #endif