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 */
 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 @try_warm is false the function issues
 50 * cold reset followed by a warm reset. If @id is 0 any valid device ID
 51 * will be accepted, otherwise only the ID that matches @id and @id_mask
 52 * is accepted.
 53 * Returns:
 54 * * %1 - if warm reset is successful
 55 * * %0 - if cold reset and warm reset is successful
 56 * * %-ENODEV - if @id and @id_mask not matching
 57 */
 58int snd_ac97_reset(struct snd_ac97 *ac97, bool try_warm, unsigned int id,
 59	unsigned int id_mask)
 60{
 61	const struct snd_ac97_bus_ops *ops = ac97->bus->ops;
 62
 63	if (try_warm && ops->warm_reset) {
 64		ops->warm_reset(ac97);
 65		if (snd_ac97_check_id(ac97, id, id_mask))
 66			return 1;
 67	}
 68
 69	if (ops->reset)
 70		ops->reset(ac97);
 71	if (ops->warm_reset)
 72		ops->warm_reset(ac97);
 73
 74	if (snd_ac97_check_id(ac97, id, id_mask))
 75		return 0;
 76
 77	return -ENODEV;
 78}
 79EXPORT_SYMBOL_GPL(snd_ac97_reset);
 80
 81const struct bus_type ac97_bus_type = {
 82	.name		= "ac97",
 83};
 84
 85static int __init ac97_bus_init(void)
 86{
 87	return bus_register(&ac97_bus_type);
 88}
 89
 90subsys_initcall(ac97_bus_init);
 91
 92static void __exit ac97_bus_exit(void)
 93{
 94	bus_unregister(&ac97_bus_type);
 95}
 96
 97module_exit(ac97_bus_exit);
 98
 99EXPORT_SYMBOL(ac97_bus_type);
100
101MODULE_DESCRIPTION("Legacy AC97 bus interface");
102MODULE_LICENSE("GPL");