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