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 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