LXR linux/sound/ac97

   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 */
  30static 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 */
  59int 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}
  80EXPORT_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 */
  87static int ac97_bus_match(struct device *dev, struct device_driver *drv)
  88{
  89        return 1;
  90}
  91
  92struct bus_type ac97_bus_type = {
  93        .name           = "ac97",
  94        .match          = ac97_bus_match,
  95};
  96
  97static int __init ac97_bus_init(void)
  98{
  99        return bus_register(&ac97_bus_type);
 100}
 101
 102subsys_initcall(ac97_bus_init);
 103
 104static void __exit ac97_bus_exit(void)
 105{
 106        bus_unregister(&ac97_bus_type);
 107}
 108
 109module_exit(ac97_bus_exit);
 110
 111EXPORT_SYMBOL(ac97_bus_type);
 112
 113MODULE_LICENSE("GPL");
 114