1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * transport_class.c - implementation of generic transport classes
4  *                     using attribute_containers
5  *
6  * Copyright (c) 2005 - James Bottomley <James.Bottomley@steeleye.com>
7  *
8  * The basic idea here is to allow any "device controller" (which
9  * would most often be a Host Bus Adapter to use the services of one
10  * or more tranport classes for performing transport specific
11  * services.  Transport specific services are things that the generic
12  * command layer doesn't want to know about (speed settings, line
13  * condidtioning, etc), but which the user might be interested in.
14  * Thus, the HBA's use the routines exported by the transport classes
15  * to perform these functions.  The transport classes export certain
16  * values to the user via sysfs using attribute containers.
17  *
18  * Note: because not every HBA will care about every transport
19  * attribute, there's a many to one relationship that goes like this:
20  *
21  * transport class<-----attribute container<----class device
22  *
23  * Usually the attribute container is per-HBA, but the design doesn't
24  * mandate that.  Although most of the services will be specific to
25  * the actual external storage connection used by the HBA, the generic
26  * transport class is framed entirely in terms of generic devices to
27  * allow it to be used by any physical HBA in the system.
28  */
29 #include <linux/export.h>
30 #include <linux/attribute_container.h>
31 #include <linux/transport_class.h>
32 
33 static int transport_remove_classdev(struct attribute_container *cont,
34 				     struct device *dev,
35 				     struct device *classdev);
36 
37 /**
38  * transport_class_register - register an initial transport class
39  *
40  * @tclass:	a pointer to the transport class structure to be initialised
41  *
42  * The transport class contains an embedded class which is used to
43  * identify it.  The caller should initialise this structure with
44  * zeros and then generic class must have been initialised with the
45  * actual transport class unique name.  There's a macro
46  * DECLARE_TRANSPORT_CLASS() to do this (declared classes still must
47  * be registered).
48  *
49  * Returns 0 on success or error on failure.
50  */
51 int transport_class_register(struct transport_class *tclass)
52 {
53 	return class_register(&tclass->class);
54 }
55 EXPORT_SYMBOL_GPL(transport_class_register);
56 
57 /**
58  * transport_class_unregister - unregister a previously registered class
59  *
60  * @tclass: The transport class to unregister
61  *
62  * Must be called prior to deallocating the memory for the transport
63  * class.
64  */
65 void transport_class_unregister(struct transport_class *tclass)
66 {
67 	class_unregister(&tclass->class);
68 }
69 EXPORT_SYMBOL_GPL(transport_class_unregister);
70 
71 static int anon_transport_dummy_function(struct transport_container *tc,
72 					 struct device *dev,
73 					 struct device *cdev)
74 {
75 	/* do nothing */
76 	return 0;
77 }
78 
79 /**
80  * anon_transport_class_register - register an anonymous class
81  *
82  * @atc: The anon transport class to register
83  *
84  * The anonymous transport class contains both a transport class and a
85  * container.  The idea of an anonymous class is that it never
86  * actually has any device attributes associated with it (and thus
87  * saves on container storage).  So it can only be used for triggering
88  * events.  Use prezero and then use DECLARE_ANON_TRANSPORT_CLASS() to
89  * initialise the anon transport class storage.
90  */
91 int anon_transport_class_register(struct anon_transport_class *atc)
92 {
93 	int error;
94 	atc->container.class = &atc->tclass.class;
95 	attribute_container_set_no_classdevs(&atc->container);
96 	error = attribute_container_register(&atc->container);
97 	if (error)
98 		return error;
99 	atc->tclass.setup = anon_transport_dummy_function;
100 	atc->tclass.remove = anon_transport_dummy_function;
101 	return 0;
102 }
103 EXPORT_SYMBOL_GPL(anon_transport_class_register);
104 
105 /**
106  * anon_transport_class_unregister - unregister an anon class
107  *
108  * @atc: Pointer to the anon transport class to unregister
109  *
110  * Must be called prior to deallocating the memory for the anon
111  * transport class.
112  */
113 void anon_transport_class_unregister(struct anon_transport_class *atc)
114 {
115 	if (unlikely(attribute_container_unregister(&atc->container)))
116 		BUG();
117 }
118 EXPORT_SYMBOL_GPL(anon_transport_class_unregister);
119 
120 static int transport_setup_classdev(struct attribute_container *cont,
121 				    struct device *dev,
122 				    struct device *classdev)
123 {
124 	struct transport_class *tclass = class_to_transport_class(cont->class);
125 	struct transport_container *tcont = attribute_container_to_transport_container(cont);
126 
127 	if (tclass->setup)
128 		tclass->setup(tcont, dev, classdev);
129 
130 	return 0;
131 }
132 
133 /**
134  * transport_setup_device - declare a new dev for transport class association but don't make it visible yet.
135  * @dev: the generic device representing the entity being added
136  *
137  * Usually, dev represents some component in the HBA system (either
138  * the HBA itself or a device remote across the HBA bus).  This
139  * routine is simply a trigger point to see if any set of transport
140  * classes wishes to associate with the added device.  This allocates
141  * storage for the class device and initialises it, but does not yet
142  * add it to the system or add attributes to it (you do this with
143  * transport_add_device).  If you have no need for a separate setup
144  * and add operations, use transport_register_device (see
145  * transport_class.h).
146  */
147 
148 void transport_setup_device(struct device *dev)
149 {
150 	attribute_container_add_device(dev, transport_setup_classdev);
151 }
152 EXPORT_SYMBOL_GPL(transport_setup_device);
153 
154 static int transport_add_class_device(struct attribute_container *cont,
155 				      struct device *dev,
156 				      struct device *classdev)
157 {
158 	int error = attribute_container_add_class_device(classdev);
159 	struct transport_container *tcont =
160 		attribute_container_to_transport_container(cont);
161 
162 	if (!error && tcont->statistics)
163 		error = sysfs_create_group(&classdev->kobj, tcont->statistics);
164 
165 	return error;
166 }
167 
168 
169 /**
170  * transport_add_device - declare a new dev for transport class association
171  *
172  * @dev: the generic device representing the entity being added
173  *
174  * Usually, dev represents some component in the HBA system (either
175  * the HBA itself or a device remote across the HBA bus).  This
176  * routine is simply a trigger point used to add the device to the
177  * system and register attributes for it.
178  */
179 int transport_add_device(struct device *dev)
180 {
181 	return attribute_container_device_trigger_safe(dev,
182 					transport_add_class_device,
183 					transport_remove_classdev);
184 }
185 EXPORT_SYMBOL_GPL(transport_add_device);
186 
187 static int transport_configure(struct attribute_container *cont,
188 			       struct device *dev,
189 			       struct device *cdev)
190 {
191 	struct transport_class *tclass = class_to_transport_class(cont->class);
192 	struct transport_container *tcont = attribute_container_to_transport_container(cont);
193 
194 	if (tclass->configure)
195 		tclass->configure(tcont, dev, cdev);
196 
197 	return 0;
198 }
199 
200 /**
201  * transport_configure_device - configure an already set up device
202  *
203  * @dev: generic device representing device to be configured
204  *
205  * The idea of configure is simply to provide a point within the setup
206  * process to allow the transport class to extract information from a
207  * device after it has been setup.  This is used in SCSI because we
208  * have to have a setup device to begin using the HBA, but after we
209  * send the initial inquiry, we use configure to extract the device
210  * parameters.  The device need not have been added to be configured.
211  */
212 void transport_configure_device(struct device *dev)
213 {
214 	attribute_container_device_trigger(dev, transport_configure);
215 }
216 EXPORT_SYMBOL_GPL(transport_configure_device);
217 
218 static int transport_remove_classdev(struct attribute_container *cont,
219 				     struct device *dev,
220 				     struct device *classdev)
221 {
222 	struct transport_container *tcont =
223 		attribute_container_to_transport_container(cont);
224 	struct transport_class *tclass = class_to_transport_class(cont->class);
225 
226 	if (tclass->remove)
227 		tclass->remove(tcont, dev, classdev);
228 
229 	if (tclass->remove != anon_transport_dummy_function) {
230 		if (tcont->statistics)
231 			sysfs_remove_group(&classdev->kobj, tcont->statistics);
232 		attribute_container_class_device_del(classdev);
233 	}
234 
235 	return 0;
236 }
237 
238 
239 /**
240  * transport_remove_device - remove the visibility of a device
241  *
242  * @dev: generic device to remove
243  *
244  * This call removes the visibility of the device (to the user from
245  * sysfs), but does not destroy it.  To eliminate a device entirely
246  * you must also call transport_destroy_device.  If you don't need to
247  * do remove and destroy as separate operations, use
248  * transport_unregister_device() (see transport_class.h) which will
249  * perform both calls for you.
250  */
251 void transport_remove_device(struct device *dev)
252 {
253 	attribute_container_device_trigger(dev, transport_remove_classdev);
254 }
255 EXPORT_SYMBOL_GPL(transport_remove_device);
256 
257 static void transport_destroy_classdev(struct attribute_container *cont,
258 				      struct device *dev,
259 				      struct device *classdev)
260 {
261 	struct transport_class *tclass = class_to_transport_class(cont->class);
262 
263 	if (tclass->remove != anon_transport_dummy_function)
264 		put_device(classdev);
265 }
266 
267 
268 /**
269  * transport_destroy_device - destroy a removed device
270  *
271  * @dev: device to eliminate from the transport class.
272  *
273  * This call triggers the elimination of storage associated with the
274  * transport classdev.  Note: all it really does is relinquish a
275  * reference to the classdev.  The memory will not be freed until the
276  * last reference goes to zero.  Note also that the classdev retains a
277  * reference count on dev, so dev too will remain for as long as the
278  * transport class device remains around.
279  */
280 void transport_destroy_device(struct device *dev)
281 {
282 	attribute_container_remove_device(dev, transport_destroy_classdev);
283 }
284 EXPORT_SYMBOL_GPL(transport_destroy_device);
285