1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Copyright (c) 2019-2020 Intel Corporation
4 *
5 * Please see Documentation/driver-api/auxiliary_bus.rst for more information.
6 */
7
8 #ifndef _AUXILIARY_BUS_H_
9 #define _AUXILIARY_BUS_H_
10
11 #include <linux/device.h>
12 #include <linux/mod_devicetable.h>
13
14 /**
15 * DOC: DEVICE_LIFESPAN
16 *
17 * The registering driver is the entity that allocates memory for the
18 * auxiliary_device and registers it on the auxiliary bus. It is important to
19 * note that, as opposed to the platform bus, the registering driver is wholly
20 * responsible for the management of the memory used for the device object.
21 *
22 * To be clear the memory for the auxiliary_device is freed in the release()
23 * callback defined by the registering driver. The registering driver should
24 * only call auxiliary_device_delete() and then auxiliary_device_uninit() when
25 * it is done with the device. The release() function is then automatically
26 * called if and when other code releases their reference to the devices.
27 *
28 * A parent object, defined in the shared header file, contains the
29 * auxiliary_device. It also contains a pointer to the shared object(s), which
30 * also is defined in the shared header. Both the parent object and the shared
31 * object(s) are allocated by the registering driver. This layout allows the
32 * auxiliary_driver's registering module to perform a container_of() call to go
33 * from the pointer to the auxiliary_device, that is passed during the call to
34 * the auxiliary_driver's probe function, up to the parent object, and then
35 * have access to the shared object(s).
36 *
37 * The memory for the shared object(s) must have a lifespan equal to, or
38 * greater than, the lifespan of the memory for the auxiliary_device. The
39 * auxiliary_driver should only consider that the shared object is valid as
40 * long as the auxiliary_device is still registered on the auxiliary bus. It
41 * is up to the registering driver to manage (e.g. free or keep available) the
42 * memory for the shared object beyond the life of the auxiliary_device.
43 *
44 * The registering driver must unregister all auxiliary devices before its own
45 * driver.remove() is completed. An easy way to ensure this is to use the
46 * devm_add_action_or_reset() call to register a function against the parent
47 * device which unregisters the auxiliary device object(s).
48 *
49 * Finally, any operations which operate on the auxiliary devices must continue
50 * to function (if only to return an error) after the registering driver
51 * unregisters the auxiliary device.
52 */
53
54 /**
55 * struct auxiliary_device - auxiliary device object.
56 * @dev: Device,
57 * The release and parent fields of the device structure must be filled
58 * in
59 * @name: Match name found by the auxiliary device driver,
60 * @id: unique identitier if multiple devices of the same name are exported,
61 * @sysfs: embedded struct which hold all sysfs related fields,
62 * @sysfs.irqs: irqs xarray contains irq indices which are used by the device,
63 * @sysfs.lock: Synchronize irq sysfs creation,
64 * @sysfs.irq_dir_exists: whether "irqs" directory exists,
65 *
66 * An auxiliary_device represents a part of its parent device's functionality.
67 * It is given a name that, combined with the registering drivers
68 * KBUILD_MODNAME, creates a match_name that is used for driver binding, and an
69 * id that combined with the match_name provide a unique name to register with
70 * the bus subsystem. For example, a driver registering an auxiliary device is
71 * named 'foo_mod.ko' and the subdevice is named 'foo_dev'. The match name is
72 * therefore 'foo_mod.foo_dev'.
73 *
74 * Registering an auxiliary_device is a three-step process.
75 *
76 * First, a 'struct auxiliary_device' needs to be defined or allocated for each
77 * sub-device desired. The name, id, dev.release, and dev.parent fields of
78 * this structure must be filled in as follows.
79 *
80 * The 'name' field is to be given a name that is recognized by the auxiliary
81 * driver. If two auxiliary_devices with the same match_name, eg
82 * "foo_mod.foo_dev", are registered onto the bus, they must have unique id
83 * values (e.g. "x" and "y") so that the registered devices names are
84 * "foo_mod.foo_dev.x" and "foo_mod.foo_dev.y". If match_name + id are not
85 * unique, then the device_add fails and generates an error message.
86 *
87 * The auxiliary_device.dev.type.release or auxiliary_device.dev.release must
88 * be populated with a non-NULL pointer to successfully register the
89 * auxiliary_device. This release call is where resources associated with the
90 * auxiliary device must be free'ed. Because once the device is placed on the
91 * bus the parent driver can not tell what other code may have a reference to
92 * this data.
93 *
94 * The auxiliary_device.dev.parent should be set. Typically to the registering
95 * drivers device.
96 *
97 * Second, call auxiliary_device_init(), which checks several aspects of the
98 * auxiliary_device struct and performs a device_initialize(). After this step
99 * completes, any error state must have a call to auxiliary_device_uninit() in
100 * its resolution path.
101 *
102 * The third and final step in registering an auxiliary_device is to perform a
103 * call to auxiliary_device_add(), which sets the name of the device and adds
104 * the device to the bus.
105 *
106 * .. code-block:: c
107 *
108 * #define MY_DEVICE_NAME "foo_dev"
109 *
110 * ...
111 *
112 * struct auxiliary_device *my_aux_dev = my_aux_dev_alloc(xxx);
113 *
114 * // Step 1:
115 * my_aux_dev->name = MY_DEVICE_NAME;
116 * my_aux_dev->id = my_unique_id_alloc(xxx);
117 * my_aux_dev->dev.release = my_aux_dev_release;
118 * my_aux_dev->dev.parent = my_dev;
119 *
120 * // Step 2:
121 * if (auxiliary_device_init(my_aux_dev))
122 * goto fail;
123 *
124 * // Step 3:
125 * if (auxiliary_device_add(my_aux_dev)) {
126 * auxiliary_device_uninit(my_aux_dev);
127 * goto fail;
128 * }
129 *
130 * ...
131 *
132 *
133 * Unregistering an auxiliary_device is a two-step process to mirror the
134 * register process. First call auxiliary_device_delete(), then call
135 * auxiliary_device_uninit().
136 *
137 * .. code-block:: c
138 *
139 * auxiliary_device_delete(my_dev->my_aux_dev);
140 * auxiliary_device_uninit(my_dev->my_aux_dev);
141 */
142 struct auxiliary_device {
143 struct device dev;
144 const char *name;
145 u32 id;
146 struct {
147 struct xarray irqs;
148 struct mutex lock; /* Synchronize irq sysfs creation */
149 bool irq_dir_exists;
150 } sysfs;
151 };
152
153 /**
154 * struct auxiliary_driver - Definition of an auxiliary bus driver
155 * @probe: Called when a matching device is added to the bus.
156 * @remove: Called when device is removed from the bus.
157 * @shutdown: Called at shut-down time to quiesce the device.
158 * @suspend: Called to put the device to sleep mode. Usually to a power state.
159 * @resume: Called to bring a device from sleep mode.
160 * @name: Driver name.
161 * @driver: Core driver structure.
162 * @id_table: Table of devices this driver should match on the bus.
163 *
164 * Auxiliary drivers follow the standard driver model convention, where
165 * discovery/enumeration is handled by the core, and drivers provide probe()
166 * and remove() methods. They support power management and shutdown
167 * notifications using the standard conventions.
168 *
169 * Auxiliary drivers register themselves with the bus by calling
170 * auxiliary_driver_register(). The id_table contains the match_names of
171 * auxiliary devices that a driver can bind with.
172 *
173 * .. code-block:: c
174 *
175 * static const struct auxiliary_device_id my_auxiliary_id_table[] = {
176 * { .name = "foo_mod.foo_dev" },
177 * {},
178 * };
179 *
180 * MODULE_DEVICE_TABLE(auxiliary, my_auxiliary_id_table);
181 *
182 * struct auxiliary_driver my_drv = {
183 * .name = "myauxiliarydrv",
184 * .id_table = my_auxiliary_id_table,
185 * .probe = my_drv_probe,
186 * .remove = my_drv_remove
187 * };
188 */
189 struct auxiliary_driver {
190 int (*probe)(struct auxiliary_device *auxdev, const struct auxiliary_device_id *id);
191 void (*remove)(struct auxiliary_device *auxdev);
192 void (*shutdown)(struct auxiliary_device *auxdev);
193 int (*suspend)(struct auxiliary_device *auxdev, pm_message_t state);
194 int (*resume)(struct auxiliary_device *auxdev);
195 const char *name;
196 struct device_driver driver;
197 const struct auxiliary_device_id *id_table;
198 };
199
200 static inline void *auxiliary_get_drvdata(struct auxiliary_device *auxdev)
201 {
202 return dev_get_drvdata(&auxdev->dev);
203 }
204
205 static inline void auxiliary_set_drvdata(struct auxiliary_device *auxdev, void *data)
206 {
207 dev_set_drvdata(&auxdev->dev, data);
208 }
209
210 static inline struct auxiliary_device *to_auxiliary_dev(struct device *dev)
211 {
212 return container_of(dev, struct auxiliary_device, dev);
213 }
214
215 static inline const struct auxiliary_driver *to_auxiliary_drv(const struct device_driver *drv)
216 {
217 return container_of(drv, struct auxiliary_driver, driver);
218 }
219
220 int auxiliary_device_init(struct auxiliary_device *auxdev);
221 int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname);
222 #define auxiliary_device_add(auxdev) __auxiliary_device_add(auxdev, KBUILD_MODNAME)
223
224 #ifdef CONFIG_SYSFS
225 int auxiliary_device_sysfs_irq_add(struct auxiliary_device *auxdev, int irq);
226 void auxiliary_device_sysfs_irq_remove(struct auxiliary_device *auxdev,
227 int irq);
228 #else /* CONFIG_SYSFS */
229 static inline int
230 auxiliary_device_sysfs_irq_add(struct auxiliary_device *auxdev, int irq)
231 {
232 return 0;
233 }
234
235 static inline void
236 auxiliary_device_sysfs_irq_remove(struct auxiliary_device *auxdev, int irq) {}
237 #endif
238
239 static inline void auxiliary_device_uninit(struct auxiliary_device *auxdev)
240 {
241 mutex_destroy(&auxdev->sysfs.lock);
242 put_device(&auxdev->dev);
243 }
244
245 static inline void auxiliary_device_delete(struct auxiliary_device *auxdev)
246 {
247 device_del(&auxdev->dev);
248 }
249
250 int __auxiliary_driver_register(struct auxiliary_driver *auxdrv, struct module *owner,
251 const char *modname);
252 #define auxiliary_driver_register(auxdrv) \
253 __auxiliary_driver_register(auxdrv, THIS_MODULE, KBUILD_MODNAME)
254
255 void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv);
256
257 /**
258 * module_auxiliary_driver() - Helper macro for registering an auxiliary driver
259 * @__auxiliary_driver: auxiliary driver struct
260 *
261 * Helper macro for auxiliary drivers which do not do anything special in
262 * module init/exit. This eliminates a lot of boilerplate. Each module may only
263 * use this macro once, and calling it replaces module_init() and module_exit()
264 *
265 * .. code-block:: c
266 *
267 * module_auxiliary_driver(my_drv);
268 */
269 #define module_auxiliary_driver(__auxiliary_driver) \
270 module_driver(__auxiliary_driver, auxiliary_driver_register, auxiliary_driver_unregister)
271
272 struct auxiliary_device *auxiliary_find_device(struct device *start,
273 const void *data,
274 int (*match)(struct device *dev, const void *data));
275
276 #endif /* _AUXILIARY_BUS_H_ */
277
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