drivers/platform/x86/firmware_attributes_class.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 /* Firmware attributes class helper module */
   4
   5 #include <linux/mutex.h>
   6 #include <linux/device/class.h>
   7 #include <linux/module.h>
   8 #include "firmware_attributes_class.h"
   9
  10 static DEFINE_MUTEX(fw_attr_lock);
  11 static int fw_attr_inuse;
  12
  13 static const struct class firmware_attributes_class = {
  14         .name = "firmware-attributes",
  15 };
  16
  17 int fw_attributes_class_get(const struct class **fw_attr_class)
  18 {
  19         int err;
  20
  21         mutex_lock(&fw_attr_lock);
  22         if (!fw_attr_inuse) { /*first time class is being used*/
  23                 err = class_register(&firmware_attributes_class);
  24                 if (err) {
  25                         mutex_unlock(&fw_attr_lock);
  26                         return err;
  27                 }
  28         }
  29         fw_attr_inuse++;
  30         *fw_attr_class = &firmware_attributes_class;
  31         mutex_unlock(&fw_attr_lock);
  32         return 0;
  33 }
  34 EXPORT_SYMBOL_GPL(fw_attributes_class_get);
  35
  36 int fw_attributes_class_put(void)
  37 {
  38         mutex_lock(&fw_attr_lock);
  39         if (!fw_attr_inuse) {
  40                 mutex_unlock(&fw_attr_lock);
  41                 return -EINVAL;
  42         }
  43         fw_attr_inuse--;
  44         if (!fw_attr_inuse) /* No more consumers */
  45                 class_unregister(&firmware_attributes_class);
  46         mutex_unlock(&fw_attr_lock);
  47         return 0;
  48 }
  49 EXPORT_SYMBOL_GPL(fw_attributes_class_put);
  50
  51 MODULE_AUTHOR("Mark Pearson <markpearson@lenovo.com>");
  52 MODULE_DESCRIPTION("Firmware attributes class helper module");
  53 MODULE_LICENSE("GPL");