drivers/base/transport_class.c

   1 /*
   2  * transport_class.c - implementation of generic transport classes
   3  *                     using attribute_containers
   4  *
   5  * Copyright (c) 2005 - James Bottomley <James.Bottomley@steeleye.com>
   6  *
   7  * This file is licensed under GPLv2
   8  *
   9  * The basic idea here is to allow any "device controller" (which
  10  * would most often be a Host Bus Adapter" to use the services of one
  11  * or more tranport classes for performing transport specific
  12  * services.  Transport specific services are things that the generic
  13  * command layer doesn't want to know about (speed settings, line
  14  * condidtioning, etc), but which the user might be interested in.
  15  * Thus, the HBA's use the routines exported by the transport classes
  16  * to perform these functions.  The transport classes export certain
  17  * values to the user via sysfs using attribute containers.
  18  *
  19  * Note: because not every HBA will care about every transport
  20  * attribute, there's a many to one relationship that goes like this:
  21  *
  22  * transport class<-----attribute container<----class device
  23  *
  24  * Usually the attribute container is per-HBA, but the design doesn't
  25  * mandate that.  Although most of the services will be specific to
  26  * the actual external storage connection used by the HBA, the generic
  27  * transport class is framed entirely in terms of generic devices to
  28  * allow it to be used by any physical HBA in the system.
  29  */
  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 device *dev)
  68 {
  69         /* do nothing */
  70         return 0;
  71 }
  72
  73 /**
  74  * anon_transport_class_register - register an anonymous class
  75  *
  76  * @atc: The anon transport class to register
  77  *
  78  * The anonymous transport class contains both a transport class and a
  79  * container.  The idea of an anonymous class is that it never
  80  * actually has any device attributes associated with it (and thus
  81  * saves on container storage).  So it can only be used for triggering
  82  * events.  Use prezero and then use DECLARE_ANON_TRANSPORT_CLASS() to
  83  * initialise the anon transport class storage.
  84  */
  85 int anon_transport_class_register(struct anon_transport_class *atc)
  86 {
  87         int error;
  88         atc->container.class = &atc->tclass.class;
  89         attribute_container_set_no_classdevs(&atc->container);
  90         error = attribute_container_register(&atc->container);
  91         if (error)
  92                 return error;
  93         atc->tclass.setup = anon_transport_dummy_function;
  94         atc->tclass.remove = anon_transport_dummy_function;
  95         return 0;
  96 }
  97 EXPORT_SYMBOL_GPL(anon_transport_class_register);
  98
  99 /**
 100  * anon_transport_class_unregister - unregister an anon class
 101  *
 102  * @atc: Pointer to the anon transport class to unregister
 103  *
 104  * Must be called prior to deallocating the memory for the anon
 105  * transport class.
 106  */
 107 void anon_transport_class_unregister(struct anon_transport_class *atc)
 108 {
 109         attribute_container_unregister(&atc->container);
 110 }
 111 EXPORT_SYMBOL_GPL(anon_transport_class_unregister);
 112
 113 static int transport_setup_classdev(struct attribute_container *cont,
 114                                     struct device *dev,
 115                                     struct class_device *classdev)
 116 {
 117         struct transport_class *tclass = class_to_transport_class(cont->class);
 118
 119         if (tclass->setup)
 120                 tclass->setup(dev);
 121
 122         return 0;
 123 }
 124
 125 /**
 126  * transport_setup_device - declare a new dev for transport class association
 127  *                          but don't make it visible yet.
 128  *
 129  * @dev: the generic device representing the entity being added
 130  *
 131  * Usually, dev represents some component in the HBA system (either
 132  * the HBA itself or a device remote across the HBA bus).  This
 133  * routine is simply a trigger point to see if any set of transport
 134  * classes wishes to associate with the added device.  This allocates
 135  * storage for the class device and initialises it, but does not yet
 136  * add it to the system or add attributes to it (you do this with
 137  * transport_add_device).  If you have no need for a separate setup
 138  * and add operations, use transport_register_device (see
 139  * transport_class.h).
 140  */
 141
 142 void transport_setup_device(struct device *dev)
 143 {
 144         attribute_container_add_device(dev, transport_setup_classdev);
 145 }
 146 EXPORT_SYMBOL_GPL(transport_setup_device);
 147
 148 static int transport_add_class_device(struct attribute_container *cont,
 149                                       struct device *dev,
 150                                       struct class_device *classdev)
 151 {
 152         int error = attribute_container_add_class_device(classdev);
 153         struct transport_container *tcont =
 154                 attribute_container_to_transport_container(cont);
 155
 156         if (!error && tcont->statistics)
 157                 error = sysfs_create_group(&classdev->kobj, tcont->statistics);
 158
 159         return error;
 160 }
 161
 162
 163 /**
 164  * transport_add_device - declare a new dev for transport class association
 165  *
 166  * @dev: the generic device representing the entity being added
 167  *
 168  * Usually, dev represents some component in the HBA system (either
 169  * the HBA itself or a device remote across the HBA bus).  This
 170  * routine is simply a trigger point used to add the device to the
 171  * system and register attributes for it.
 172  */
 173
 174 void transport_add_device(struct device *dev)
 175 {
 176         attribute_container_device_trigger(dev, transport_add_class_device);
 177 }
 178 EXPORT_SYMBOL_GPL(transport_add_device);
 179
 180 static int transport_configure(struct attribute_container *cont,
 181                                struct device *dev)
 182 {
 183         struct transport_class *tclass = class_to_transport_class(cont->class);
 184
 185         if (tclass->configure)
 186                 tclass->configure(dev);
 187
 188         return 0;
 189 }
 190
 191 /**
 192  * transport_configure_device - configure an already set up device
 193  *
 194  * @dev: generic device representing device to be configured
 195  *
 196  * The idea of configure is simply to provide a point within the setup
 197  * process to allow the transport class to extract information from a
 198  * device after it has been setup.  This is used in SCSI because we
 199  * have to have a setup device to begin using the HBA, but after we
 200  * send the initial inquiry, we use configure to extract the device
 201  * parameters.  The device need not have been added to be configured.
 202  */
 203 void transport_configure_device(struct device *dev)
 204 {
 205         attribute_container_trigger(dev, transport_configure);
 206 }
 207 EXPORT_SYMBOL_GPL(transport_configure_device);
 208
 209 static int transport_remove_classdev(struct attribute_container *cont,
 210                                      struct device *dev,
 211                                      struct class_device *classdev)
 212 {
 213         struct transport_container *tcont =
 214                 attribute_container_to_transport_container(cont);
 215         struct transport_class *tclass = class_to_transport_class(cont->class);
 216
 217         if (tclass->remove)
 218                 tclass->remove(dev);
 219
 220         if (tclass->remove != anon_transport_dummy_function) {
 221                 if (tcont->statistics)
 222                         sysfs_remove_group(&classdev->kobj, tcont->statistics);
 223                 attribute_container_class_device_del(classdev);
 224         }
 225
 226         return 0;
 227 }
 228
 229
 230 /**
 231  * transport_remove_device - remove the visibility of a device
 232  *
 233  * @dev: generic device to remove
 234  *
 235  * This call removes the visibility of the device (to the user from
 236  * sysfs), but does not destroy it.  To eliminate a device entirely
 237  * you must also call transport_destroy_device.  If you don't need to
 238  * do remove and destroy as separate operations, use
 239  * transport_unregister_device() (see transport_class.h) which will
 240  * perform both calls for you.
 241  */
 242 void transport_remove_device(struct device *dev)
 243 {
 244         attribute_container_device_trigger(dev, transport_remove_classdev);
 245 }
 246 EXPORT_SYMBOL_GPL(transport_remove_device);
 247
 248 static void transport_destroy_classdev(struct attribute_container *cont,
 249                                       struct device *dev,
 250                                       struct class_device *classdev)
 251 {
 252         struct transport_class *tclass = class_to_transport_class(cont->class);
 253
 254         if (tclass->remove != anon_transport_dummy_function)
 255                 class_device_put(classdev);
 256 }
 257
 258
 259 /**
 260  * transport_destroy_device - destroy a removed device
 261  *
 262  * @dev: device to eliminate from the transport class.
 263  *
 264  * This call triggers the elimination of storage associated with the
 265  * transport classdev.  Note: all it really does is relinquish a
 266  * reference to the classdev.  The memory will not be freed until the
 267  * last reference goes to zero.  Note also that the classdev retains a
 268  * reference count on dev, so dev too will remain for as long as the
 269  * transport class device remains around.
 270  */
 271 void transport_destroy_device(struct device *dev)
 272 {
 273         attribute_container_remove_device(dev, transport_destroy_classdev);
 274 }
 275 EXPORT_SYMBOL_GPL(transport_destroy_device);