linux/sound/ac97_bus.c
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   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 */
  26static 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 */
  55int 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}
  76EXPORT_SYMBOL_GPL(snd_ac97_reset);
  77
  78struct bus_type ac97_bus_type = {
  79        .name           = "ac97",
  80};
  81
  82static int __init ac97_bus_init(void)
  83{
  84        return bus_register(&ac97_bus_type);
  85}
  86
  87subsys_initcall(ac97_bus_init);
  88
  89static void __exit ac97_bus_exit(void)
  90{
  91        bus_unregister(&ac97_bus_type);
  92}
  93
  94module_exit(ac97_bus_exit);
  95
  96EXPORT_SYMBOL(ac97_bus_type);
  97
  98MODULE_LICENSE("GPL");
  99