xref: /openbmc/linux/sound/ac97_bus.c (revision be58f710)
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");
110