sound/ac97_bus.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Linux driver model AC97 bus interface
   4  *
   5  * Author:      Nicolas Pitre
   6  * Created:     Jan 14, 2005
   7  * Copyright:   (C) MontaVista Software Inc.
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/device.h>
  13 #include <linux/string.h>
  14 #include <sound/ac97_codec.h>
  15
  16 /*
  17  * snd_ac97_check_id() - Reads and checks the vendor ID of the device
  18  * @ac97: The AC97 device to check
  19  * @id: The ID to compare to
  20  * @id_mask: Mask that is applied to the device ID before comparing to @id
  21  *
  22  * If @id is 0 this function returns true if the read device vendor ID is
  23  * a valid ID. If @id is non 0 this functions returns true if @id
  24  * matches the read vendor ID. Otherwise the function returns false.
  25  */
  26 static bool snd_ac97_check_id(struct snd_ac97 *ac97, unsigned int id,
  27         unsigned int id_mask)
  28 {
  29         ac97->id = ac97->bus->ops->read(ac97, AC97_VENDOR_ID1) << 16;
  30         ac97->id |= ac97->bus->ops->read(ac97, AC97_VENDOR_ID2);
  31
  32         if (ac97->id == 0x0 || ac97->id == 0xffffffff)
  33                 return false;
  34
  35         if (id != 0 && id != (ac97->id & id_mask))
  36                 return false;
  37
  38         return true;
  39 }
  40
  41 /**
  42  * snd_ac97_reset() - Reset AC'97 device
  43  * @ac97: The AC'97 device to reset
  44  * @try_warm: Try a warm reset first
  45  * @id: Expected device vendor ID
  46  * @id_mask: Mask that is applied to the device ID before comparing to @id
  47  *
  48  * This function resets the AC'97 device. If @try_warm is true the function
  49  * first performs a warm reset. If the warm reset is successful the function
  50  * returns 1. Otherwise or if @try_warm is false the function issues cold reset
  51  * followed by a warm reset. If this is successful the function returns 0,
  52  * otherwise a negative error code. If @id is 0 any valid device ID will be
  53  * accepted, otherwise only the ID that matches @id and @id_mask is accepted.
  54  */
  55 int snd_ac97_reset(struct snd_ac97 *ac97, bool try_warm, unsigned int id,
  56         unsigned int id_mask)
  57 {
  58         const struct snd_ac97_bus_ops *ops = ac97->bus->ops;
  59
  60         if (try_warm && ops->warm_reset) {
  61                 ops->warm_reset(ac97);
  62                 if (snd_ac97_check_id(ac97, id, id_mask))
  63                         return 1;
  64         }
  65
  66         if (ops->reset)
  67                 ops->reset(ac97);
  68         if (ops->warm_reset)
  69                 ops->warm_reset(ac97);
  70
  71         if (snd_ac97_check_id(ac97, id, id_mask))
  72                 return 0;
  73
  74         return -ENODEV;
  75 }
  76 EXPORT_SYMBOL_GPL(snd_ac97_reset);
  77
  78 /*
  79  * Let drivers decide whether they want to support given codec from their
  80  * probe method. Drivers have direct access to the struct snd_ac97
  81  * structure and may  decide based on the id field amongst other things.
  82  */
  83 static int ac97_bus_match(struct device *dev, struct device_driver *drv)
  84 {
  85         return 1;
  86 }
  87
  88 struct bus_type ac97_bus_type = {
  89         .name           = "ac97",
  90         .match          = ac97_bus_match,
  91 };
  92
  93 static int __init ac97_bus_init(void)
  94 {
  95         return bus_register(&ac97_bus_type);
  96 }
  97
  98 subsys_initcall(ac97_bus_init);
  99
 100 static void __exit ac97_bus_exit(void)
 101 {
 102         bus_unregister(&ac97_bus_type);
 103 }
 104
 105 module_exit(ac97_bus_exit);
 106
 107 EXPORT_SYMBOL(ac97_bus_type);
 108
 109 MODULE_LICENSE("GPL");