drivers/base/transport_class.c

   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);