sound/ac97_bus.c

   1 /*
   2  * Linux driver model AC97 bus interface
   3  *
   4  * Author:      Nicolas Pitre
   5  * Created:     Jan 14, 2005
   6  * Copyright:   (C) MontaVista Software Inc.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/init.h>
  16 #include <linux/device.h>
  17 #include <linux/string.h>
  18 #include <sound/ac97_codec.h>
  19
  20 /*
  21  * snd_ac97_check_id() - Reads and checks the vendor ID of the device
  22  * @ac97: The AC97 device to check
  23  * @id: The ID to compare to
  24  * @id_mask: Mask that is applied to the device ID before comparing to @id
  25  *
  26  * If @id is 0 this function returns true if the read device vendor ID is
  27  * a valid ID. If @id is non 0 this functions returns true if @id
  28  * matches the read vendor ID. Otherwise the function returns false.
  29  */
  30 static bool snd_ac97_check_id(struct snd_ac97 *ac97, unsigned int id,
  31         unsigned int id_mask)
  32 {
  33         ac97->id = ac97->bus->ops->read(ac97, AC97_VENDOR_ID1) << 16;
  34         ac97->id |= ac97->bus->ops->read(ac97, AC97_VENDOR_ID2);
  35
  36         if (ac97->id == 0x0 || ac97->id == 0xffffffff)
  37                 return false;
  38
  39         if (id != 0 && id != (ac97->id & id_mask))
  40                 return false;
  41
  42         return true;
  43 }
  44
  45 /**
  46  * snd_ac97_reset() - Reset AC'97 device
  47  * @ac97: The AC'97 device to reset
  48  * @try_warm: Try a warm reset first
  49  * @id: Expected device vendor ID
  50  * @id_mask: Mask that is applied to the device ID before comparing to @id
  51  *
  52  * This function resets the AC'97 device. If @try_warm is true the function
  53  * first performs a warm reset. If the warm reset is successful the function
  54  * returns 1. Otherwise or if @try_warm is false the function issues cold reset
  55  * followed by a warm reset. If this is successful the function returns 0,
  56  * otherwise a negative error code. If @id is 0 any valid device ID will be
  57  * accepted, otherwise only the ID that matches @id and @id_mask is accepted.
  58  */
  59 int snd_ac97_reset(struct snd_ac97 *ac97, bool try_warm, unsigned int id,
  60         unsigned int id_mask)
  61 {
  62         struct snd_ac97_bus_ops *ops = ac97->bus->ops;
  63
  64         if (try_warm && ops->warm_reset) {
  65                 ops->warm_reset(ac97);
  66                 if (snd_ac97_check_id(ac97, id, id_mask))
  67                         return 1;
  68         }
  69
  70         if (ops->reset)
  71                 ops->reset(ac97);
  72         if (ops->warm_reset)
  73                 ops->warm_reset(ac97);
  74
  75         if (snd_ac97_check_id(ac97, id, id_mask))
  76                 return 0;
  77
  78         return -ENODEV;
  79 }
  80 EXPORT_SYMBOL_GPL(snd_ac97_reset);
  81
  82 /*
  83  * Let drivers decide whether they want to support given codec from their
  84  * probe method. Drivers have direct access to the struct snd_ac97
  85  * structure and may  decide based on the id field amongst other things.
  86  */
  87 static int ac97_bus_match(struct device *dev, struct device_driver *drv)
  88 {
  89         return 1;
  90 }
  91
  92 struct bus_type ac97_bus_type = {
  93         .name           = "ac97",
  94         .match          = ac97_bus_match,
  95 };
  96
  97 static int __init ac97_bus_init(void)
  98 {
  99         return bus_register(&ac97_bus_type);
 100 }
 101
 102 subsys_initcall(ac97_bus_init);
 103
 104 static void __exit ac97_bus_exit(void)
 105 {
 106         bus_unregister(&ac97_bus_type);
 107 }
 108
 109 module_exit(ac97_bus_exit);
 110
 111 EXPORT_SYMBOL(ac97_bus_type);
 112
 113 MODULE_LICENSE("GPL");