root/samples/configfs/configfs_sample.c

DEFINITIONS

1. to_childless
2. childless_showme_show
3. childless_storeme_show
4. childless_storeme_store
5. childless_description_show
6. to_simple_child
7. simple_child_storeme_show
8. simple_child_storeme_store
9. simple_child_release
10. to_simple_children
11. simple_children_make_item
12. simple_children_description_show
13. simple_children_release
14. group_children_make_group
15. group_children_description_show
16. configfs_example_init
17. configfs_example_exit

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * vim: noexpandtab ts=8 sts=0 sw=8:
   4  *
   5  * configfs_example_macros.c - This file is a demonstration module
   6  *      containing a number of configfs subsystems.  It uses the helper
   7  *      macros defined by configfs.h
   8  *
   9  * Based on sysfs:
  10  *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
  11  *
  12  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
  13  */
  14 
  15 #include <linux/init.h>
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 
  19 #include <linux/configfs.h>
  20 
  21 
  22 
  23 /*
  24  * 01-childless
  25  *
  26  * This first example is a childless subsystem.  It cannot create
  27  * any config_items.  It just has attributes.
  28  *
  29  * Note that we are enclosing the configfs_subsystem inside a container.
  30  * This is not necessary if a subsystem has no attributes directly
  31  * on the subsystem.  See the next example, 02-simple-children, for
  32  * such a subsystem.
  33  */
  34 
  35 struct childless {
  36         struct configfs_subsystem subsys;
  37         int showme;
  38         int storeme;
  39 };
  40 
  41 static inline struct childless *to_childless(struct config_item *item)
  42 {
  43         return item ? container_of(to_configfs_subsystem(to_config_group(item)),
  44                         struct childless, subsys) : NULL;
  45 }
  46 
  47 static ssize_t childless_showme_show(struct config_item *item, char *page)
  48 {
  49         struct childless *childless = to_childless(item);
  50         ssize_t pos;
  51 
  52         pos = sprintf(page, "%d\n", childless->showme);
  53         childless->showme++;
  54 
  55         return pos;
  56 }
  57 
  58 static ssize_t childless_storeme_show(struct config_item *item, char *page)
  59 {
  60         return sprintf(page, "%d\n", to_childless(item)->storeme);
  61 }
  62 
  63 static ssize_t childless_storeme_store(struct config_item *item,
  64                 const char *page, size_t count)
  65 {
  66         struct childless *childless = to_childless(item);
  67         unsigned long tmp;
  68         char *p = (char *) page;
  69 
  70         tmp = simple_strtoul(p, &p, 10);
  71         if (!p || (*p && (*p != '\n')))
  72                 return -EINVAL;
  73 
  74         if (tmp > INT_MAX)
  75                 return -ERANGE;
  76 
  77         childless->storeme = tmp;
  78 
  79         return count;
  80 }
  81 
  82 static ssize_t childless_description_show(struct config_item *item, char *page)
  83 {
  84         return sprintf(page,
  85 "[01-childless]\n"
  86 "\n"
  87 "The childless subsystem is the simplest possible subsystem in\n"
  88 "configfs.  It does not support the creation of child config_items.\n"
  89 "It only has a few attributes.  In fact, it isn't much different\n"
  90 "than a directory in /proc.\n");
  91 }
  92 
  93 CONFIGFS_ATTR_RO(childless_, showme);
  94 CONFIGFS_ATTR(childless_, storeme);
  95 CONFIGFS_ATTR_RO(childless_, description);
  96 
  97 static struct configfs_attribute *childless_attrs[] = {
  98         &childless_attr_showme,
  99         &childless_attr_storeme,
 100         &childless_attr_description,
 101         NULL,
 102 };
 103 
 104 static const struct config_item_type childless_type = {
 105         .ct_attrs       = childless_attrs,
 106         .ct_owner       = THIS_MODULE,
 107 };
 108 
 109 static struct childless childless_subsys = {
 110         .subsys = {
 111                 .su_group = {
 112                         .cg_item = {
 113                                 .ci_namebuf = "01-childless",
 114                                 .ci_type = &childless_type,
 115                         },
 116                 },
 117         },
 118 };
 119 
 120 
 121 /* ----------------------------------------------------------------- */
 122 
 123 /*
 124  * 02-simple-children
 125  *
 126  * This example merely has a simple one-attribute child.  Note that
 127  * there is no extra attribute structure, as the child's attribute is
 128  * known from the get-go.  Also, there is no container for the
 129  * subsystem, as it has no attributes of its own.
 130  */
 131 
 132 struct simple_child {
 133         struct config_item item;
 134         int storeme;
 135 };
 136 
 137 static inline struct simple_child *to_simple_child(struct config_item *item)
 138 {
 139         return item ? container_of(item, struct simple_child, item) : NULL;
 140 }
 141 
 142 static ssize_t simple_child_storeme_show(struct config_item *item, char *page)
 143 {
 144         return sprintf(page, "%d\n", to_simple_child(item)->storeme);
 145 }
 146 
 147 static ssize_t simple_child_storeme_store(struct config_item *item,
 148                 const char *page, size_t count)
 149 {
 150         struct simple_child *simple_child = to_simple_child(item);
 151         unsigned long tmp;
 152         char *p = (char *) page;
 153 
 154         tmp = simple_strtoul(p, &p, 10);
 155         if (!p || (*p && (*p != '\n')))
 156                 return -EINVAL;
 157 
 158         if (tmp > INT_MAX)
 159                 return -ERANGE;
 160 
 161         simple_child->storeme = tmp;
 162 
 163         return count;
 164 }
 165 
 166 CONFIGFS_ATTR(simple_child_, storeme);
 167 
 168 static struct configfs_attribute *simple_child_attrs[] = {
 169         &simple_child_attr_storeme,
 170         NULL,
 171 };
 172 
 173 static void simple_child_release(struct config_item *item)
 174 {
 175         kfree(to_simple_child(item));
 176 }
 177 
 178 static struct configfs_item_operations simple_child_item_ops = {
 179         .release                = simple_child_release,
 180 };
 181 
 182 static const struct config_item_type simple_child_type = {
 183         .ct_item_ops    = &simple_child_item_ops,
 184         .ct_attrs       = simple_child_attrs,
 185         .ct_owner       = THIS_MODULE,
 186 };
 187 
 188 
 189 struct simple_children {
 190         struct config_group group;
 191 };
 192 
 193 static inline struct simple_children *to_simple_children(struct config_item *item)
 194 {
 195         return item ? container_of(to_config_group(item),
 196                         struct simple_children, group) : NULL;
 197 }
 198 
 199 static struct config_item *simple_children_make_item(struct config_group *group,
 200                 const char *name)
 201 {
 202         struct simple_child *simple_child;
 203 
 204         simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
 205         if (!simple_child)
 206                 return ERR_PTR(-ENOMEM);
 207 
 208         config_item_init_type_name(&simple_child->item, name,
 209                                    &simple_child_type);
 210 
 211         simple_child->storeme = 0;
 212 
 213         return &simple_child->item;
 214 }
 215 
 216 static ssize_t simple_children_description_show(struct config_item *item,
 217                 char *page)
 218 {
 219         return sprintf(page,
 220 "[02-simple-children]\n"
 221 "\n"
 222 "This subsystem allows the creation of child config_items.  These\n"
 223 "items have only one attribute that is readable and writeable.\n");
 224 }
 225 
 226 CONFIGFS_ATTR_RO(simple_children_, description);
 227 
 228 static struct configfs_attribute *simple_children_attrs[] = {
 229         &simple_children_attr_description,
 230         NULL,
 231 };
 232 
 233 static void simple_children_release(struct config_item *item)
 234 {
 235         kfree(to_simple_children(item));
 236 }
 237 
 238 static struct configfs_item_operations simple_children_item_ops = {
 239         .release        = simple_children_release,
 240 };
 241 
 242 /*
 243  * Note that, since no extra work is required on ->drop_item(),
 244  * no ->drop_item() is provided.
 245  */
 246 static struct configfs_group_operations simple_children_group_ops = {
 247         .make_item      = simple_children_make_item,
 248 };
 249 
 250 static const struct config_item_type simple_children_type = {
 251         .ct_item_ops    = &simple_children_item_ops,
 252         .ct_group_ops   = &simple_children_group_ops,
 253         .ct_attrs       = simple_children_attrs,
 254         .ct_owner       = THIS_MODULE,
 255 };
 256 
 257 static struct configfs_subsystem simple_children_subsys = {
 258         .su_group = {
 259                 .cg_item = {
 260                         .ci_namebuf = "02-simple-children",
 261                         .ci_type = &simple_children_type,
 262                 },
 263         },
 264 };
 265 
 266 
 267 /* ----------------------------------------------------------------- */
 268 
 269 /*
 270  * 03-group-children
 271  *
 272  * This example reuses the simple_children group from above.  However,
 273  * the simple_children group is not the subsystem itself, it is a
 274  * child of the subsystem.  Creation of a group in the subsystem creates
 275  * a new simple_children group.  That group can then have simple_child
 276  * children of its own.
 277  */
 278 
 279 static struct config_group *group_children_make_group(
 280                 struct config_group *group, const char *name)
 281 {
 282         struct simple_children *simple_children;
 283 
 284         simple_children = kzalloc(sizeof(struct simple_children),
 285                                   GFP_KERNEL);
 286         if (!simple_children)
 287                 return ERR_PTR(-ENOMEM);
 288 
 289         config_group_init_type_name(&simple_children->group, name,
 290                                     &simple_children_type);
 291 
 292         return &simple_children->group;
 293 }
 294 
 295 static ssize_t group_children_description_show(struct config_item *item,
 296                 char *page)
 297 {
 298         return sprintf(page,
 299 "[03-group-children]\n"
 300 "\n"
 301 "This subsystem allows the creation of child config_groups.  These\n"
 302 "groups are like the subsystem simple-children.\n");
 303 }
 304 
 305 CONFIGFS_ATTR_RO(group_children_, description);
 306 
 307 static struct configfs_attribute *group_children_attrs[] = {
 308         &group_children_attr_description,
 309         NULL,
 310 };
 311 
 312 /*
 313  * Note that, since no extra work is required on ->drop_item(),
 314  * no ->drop_item() is provided.
 315  */
 316 static struct configfs_group_operations group_children_group_ops = {
 317         .make_group     = group_children_make_group,
 318 };
 319 
 320 static const struct config_item_type group_children_type = {
 321         .ct_group_ops   = &group_children_group_ops,
 322         .ct_attrs       = group_children_attrs,
 323         .ct_owner       = THIS_MODULE,
 324 };
 325 
 326 static struct configfs_subsystem group_children_subsys = {
 327         .su_group = {
 328                 .cg_item = {
 329                         .ci_namebuf = "03-group-children",
 330                         .ci_type = &group_children_type,
 331                 },
 332         },
 333 };
 334 
 335 /* ----------------------------------------------------------------- */
 336 
 337 /*
 338  * We're now done with our subsystem definitions.
 339  * For convenience in this module, here's a list of them all.  It
 340  * allows the init function to easily register them.  Most modules
 341  * will only have one subsystem, and will only call register_subsystem
 342  * on it directly.
 343  */
 344 static struct configfs_subsystem *example_subsys[] = {
 345         &childless_subsys.subsys,
 346         &simple_children_subsys,
 347         &group_children_subsys,
 348         NULL,
 349 };
 350 
 351 static int __init configfs_example_init(void)
 352 {
 353         int ret;
 354         int i;
 355         struct configfs_subsystem *subsys;
 356 
 357         for (i = 0; example_subsys[i]; i++) {
 358                 subsys = example_subsys[i];
 359 
 360                 config_group_init(&subsys->su_group);
 361                 mutex_init(&subsys->su_mutex);
 362                 ret = configfs_register_subsystem(subsys);
 363                 if (ret) {
 364                         printk(KERN_ERR "Error %d while registering subsystem %s\n",
 365                                ret,
 366                                subsys->su_group.cg_item.ci_namebuf);
 367                         goto out_unregister;
 368                 }
 369         }
 370 
 371         return 0;
 372 
 373 out_unregister:
 374         for (i--; i >= 0; i--)
 375                 configfs_unregister_subsystem(example_subsys[i]);
 376 
 377         return ret;
 378 }
 379 
 380 static void __exit configfs_example_exit(void)
 381 {
 382         int i;
 383 
 384         for (i = 0; example_subsys[i]; i++)
 385                 configfs_unregister_subsystem(example_subsys[i]);
 386 }
 387 
 388 module_init(configfs_example_init);
 389 module_exit(configfs_example_exit);
 390 MODULE_LICENSE("GPL");