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);
280