target/linux/brcm2708/patches-4.4/0178-OF-DT-Overlay-configfs-interface.patch

   1 From 837aeb8b5e162873fe687e788c74984645e83964 Mon Sep 17 00:00:00 2001
   2 From: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
   3 Date: Wed, 3 Dec 2014 13:23:28 +0200
   4 Subject: [PATCH] OF: DT-Overlay configfs interface
   5
   6 This is a port of Pantelis Antoniou's v3 port that makes use of the
   7 new upstreamed configfs support for binary attributes.
   8
   9 Original commit message:
  10
  11 Add a runtime interface to using configfs for generic device tree overlay
  12 usage. With it its possible to use device tree overlays without having
  13 to use a per-platform overlay manager.
  14
  15 Please see Documentation/devicetree/configfs-overlays.txt for more info.
  16
  17 Changes since v2:
  18 - Removed ifdef CONFIG_OF_OVERLAY (since for now it's required)
  19 - Created a documentation entry
  20 - Slight rewording in Kconfig
  21
  22 Changes since v1:
  23 - of_resolve() -> of_resolve_phandles().
  24
  25 Originally-signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
  26 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
  27 ---
  28  Documentation/devicetree/configfs-overlays.txt |  31 +++
  29  drivers/of/Kconfig                             |   7 +
  30  drivers/of/Makefile                            |   1 +
  31  drivers/of/configfs.c                          | 314 +++++++++++++++++++++++++
  32  4 files changed, 353 insertions(+)
  33  create mode 100644 Documentation/devicetree/configfs-overlays.txt
  34  create mode 100644 drivers/of/configfs.c
  35
  36 --- /dev/null
  37 +++ b/Documentation/devicetree/configfs-overlays.txt
  38 @@ -0,0 +1,31 @@
  39 +Howto use the configfs overlay interface.
  40 +
  41 +A device-tree configfs entry is created in /config/device-tree/overlays
  42 +and and it is manipulated using standard file system I/O.
  43 +Note that this is a debug level interface, for use by developers and
  44 +not necessarily something accessed by normal users due to the
  45 +security implications of having direct access to the kernel's device tree.
  46 +
  47 +* To create an overlay you mkdir the directory:
  48 +
  49 +       # mkdir /config/device-tree/overlays/foo
  50 +
  51 +* Either you echo the overlay firmware file to the path property file.
  52 +
  53 +       # echo foo.dtbo >/config/device-tree/overlays/foo/path
  54 +
  55 +* Or you cat the contents of the overlay to the dtbo file
  56 +
  57 +       # cat foo.dtbo >/config/device-tree/overlays/foo/dtbo
  58 +
  59 +The overlay file will be applied, and devices will be created/destroyed
  60 +as required.
  61 +
  62 +To remove it simply rmdir the directory.
  63 +
  64 +       # rmdir /config/device-tree/overlays/foo
  65 +
  66 +The rationalle of the dual interface (firmware & direct copy) is that each is
  67 +better suited to different use patterns. The firmware interface is what's
  68 +intended to be used by hardware managers in the kernel, while the copy interface
  69 +make sense for developers (since it avoids problems with namespaces).
  70 --- a/drivers/of/Kconfig
  71 +++ b/drivers/of/Kconfig
  72 @@ -112,4 +112,11 @@ config OF_OVERLAY
  73           While this option is selected automatically when needed, you can
  74           enable it manually to improve device tree unit test coverage.
  75
  76 +config OF_CONFIGFS
  77 +       bool "Device Tree Overlay ConfigFS interface"
  78 +       select CONFIGFS_FS
  79 +       select OF_OVERLAY
  80 +       help
  81 +         Enable a simple user-space driven DT overlay interface.
  82 +
  83  endif # OF
  84 --- a/drivers/of/Makefile
  85 +++ b/drivers/of/Makefile
  86 @@ -1,4 +1,5 @@
  87  obj-y = base.o device.o platform.o
  88 +obj-$(CONFIG_OF_CONFIGFS) += configfs.o
  89  obj-$(CONFIG_OF_DYNAMIC) += dynamic.o
  90  obj-$(CONFIG_OF_FLATTREE) += fdt.o
  91  obj-$(CONFIG_OF_EARLY_FLATTREE) += fdt_address.o
  92 --- /dev/null
  93 +++ b/drivers/of/configfs.c
  94 @@ -0,0 +1,314 @@
  95 +/*
  96 + * Configfs entries for device-tree
  97 + *
  98 + * Copyright (C) 2013 - Pantelis Antoniou <panto@antoniou-consulting.com>
  99 + *
 100 + * This program is free software; you can redistribute it and/or
 101 + * modify it under the terms of the GNU General Public License
 102 + * as published by the Free Software Foundation; either version
 103 + * 2 of the License, or (at your option) any later version.
 104 + */
 105 +#include <linux/ctype.h>
 106 +#include <linux/cpu.h>
 107 +#include <linux/module.h>
 108 +#include <linux/of.h>
 109 +#include <linux/of_fdt.h>
 110 +#include <linux/spinlock.h>
 111 +#include <linux/slab.h>
 112 +#include <linux/proc_fs.h>
 113 +#include <linux/configfs.h>
 114 +#include <linux/types.h>
 115 +#include <linux/stat.h>
 116 +#include <linux/limits.h>
 117 +#include <linux/file.h>
 118 +#include <linux/vmalloc.h>
 119 +#include <linux/firmware.h>
 120 +
 121 +#include "of_private.h"
 122 +
 123 +struct cfs_overlay_item {
 124 +       struct config_item      item;
 125 +
 126 +       char                    path[PATH_MAX];
 127 +
 128 +       const struct firmware   *fw;
 129 +       struct device_node      *overlay;
 130 +       int                     ov_id;
 131 +
 132 +       void                    *dtbo;
 133 +       int                     dtbo_size;
 134 +};
 135 +
 136 +static int create_overlay(struct cfs_overlay_item *overlay, void *blob)
 137 +{
 138 +       int err;
 139 +
 140 +       /* unflatten the tree */
 141 +       of_fdt_unflatten_tree(blob, &overlay->overlay);
 142 +       if (overlay->overlay == NULL) {
 143 +               pr_err("%s: failed to unflatten tree\n", __func__);
 144 +               err = -EINVAL;
 145 +               goto out_err;
 146 +       }
 147 +       pr_debug("%s: unflattened OK\n", __func__);
 148 +
 149 +       /* mark it as detached */
 150 +       of_node_set_flag(overlay->overlay, OF_DETACHED);
 151 +
 152 +       /* perform resolution */
 153 +       err = of_resolve_phandles(overlay->overlay);
 154 +       if (err != 0) {
 155 +               pr_err("%s: Failed to resolve tree\n", __func__);
 156 +               goto out_err;
 157 +       }
 158 +       pr_debug("%s: resolved OK\n", __func__);
 159 +
 160 +       err = of_overlay_create(overlay->overlay);
 161 +       if (err < 0) {
 162 +               pr_err("%s: Failed to create overlay (err=%d)\n",
 163 +                               __func__, err);
 164 +               goto out_err;
 165 +       }
 166 +       overlay->ov_id = err;
 167 +
 168 +out_err:
 169 +       return err;
 170 +}
 171 +
 172 +static inline struct cfs_overlay_item *to_cfs_overlay_item(
 173 +               struct config_item *item)
 174 +{
 175 +       return item ? container_of(item, struct cfs_overlay_item, item) : NULL;
 176 +}
 177 +
 178 +static ssize_t cfs_overlay_item_path_show(struct config_item *item,
 179 +               char *page)
 180 +{
 181 +       struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
 182 +       return sprintf(page, "%s\n", overlay->path);
 183 +}
 184 +
 185 +static ssize_t cfs_overlay_item_path_store(struct config_item *item,
 186 +               const char *page, size_t count)
 187 +{
 188 +       struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
 189 +       const char *p = page;
 190 +       char *s;
 191 +       int err;
 192 +
 193 +       /* if it's set do not allow changes */
 194 +       if (overlay->path[0] != '\0' || overlay->dtbo_size > 0)
 195 +               return -EPERM;
 196 +
 197 +       /* copy to path buffer (and make sure it's always zero terminated */
 198 +       count = snprintf(overlay->path, sizeof(overlay->path) - 1, "%s", p);
 199 +       overlay->path[sizeof(overlay->path) - 1] = '\0';
 200 +
 201 +       /* strip trailing newlines */
 202 +       s = overlay->path + strlen(overlay->path);
 203 +       while (s > overlay->path && *--s == '\n')
 204 +               *s = '\0';
 205 +
 206 +       pr_debug("%s: path is '%s'\n", __func__, overlay->path);
 207 +
 208 +       err = request_firmware(&overlay->fw, overlay->path, NULL);
 209 +       if (err != 0)
 210 +               goto out_err;
 211 +
 212 +       err = create_overlay(overlay, (void *)overlay->fw->data);
 213 +       if (err != 0)
 214 +               goto out_err;
 215 +
 216 +       return count;
 217 +
 218 +out_err:
 219 +
 220 +       release_firmware(overlay->fw);
 221 +       overlay->fw = NULL;
 222 +
 223 +       overlay->path[0] = '\0';
 224 +       return err;
 225 +}
 226 +
 227 +static ssize_t cfs_overlay_item_status_show(struct config_item *item,
 228 +               char *page)
 229 +{
 230 +       struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
 231 +
 232 +       return sprintf(page, "%s\n",
 233 +                       overlay->ov_id >= 0 ? "applied" : "unapplied");
 234 +}
 235 +
 236 +CONFIGFS_ATTR(cfs_overlay_item_, path);
 237 +CONFIGFS_ATTR_RO(cfs_overlay_item_, status);
 238 +
 239 +static struct configfs_attribute *cfs_overlay_attrs[] = {
 240 +       &cfs_overlay_item_attr_path,
 241 +       &cfs_overlay_item_attr_status,
 242 +       NULL,
 243 +};
 244 +
 245 +ssize_t cfs_overlay_item_dtbo_read(struct config_item *item,
 246 +               void *buf, size_t max_count)
 247 +{
 248 +       struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
 249 +
 250 +       pr_debug("%s: buf=%p max_count=%u\n", __func__,
 251 +                       buf, max_count);
 252 +
 253 +       if (overlay->dtbo == NULL)
 254 +               return 0;
 255 +
 256 +       /* copy if buffer provided */
 257 +       if (buf != NULL) {
 258 +               /* the buffer must be large enough */
 259 +               if (overlay->dtbo_size > max_count)
 260 +                       return -ENOSPC;
 261 +
 262 +               memcpy(buf, overlay->dtbo, overlay->dtbo_size);
 263 +       }
 264 +
 265 +       return overlay->dtbo_size;
 266 +}
 267 +
 268 +ssize_t cfs_overlay_item_dtbo_write(struct config_item *item,
 269 +               const void *buf, size_t count)
 270 +{
 271 +       struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
 272 +       int err;
 273 +
 274 +       /* if it's set do not allow changes */
 275 +       if (overlay->path[0] != '\0' || overlay->dtbo_size > 0)
 276 +               return -EPERM;
 277 +
 278 +       /* copy the contents */
 279 +       overlay->dtbo = kmemdup(buf, count, GFP_KERNEL);
 280 +       if (overlay->dtbo == NULL)
 281 +               return -ENOMEM;
 282 +
 283 +       overlay->dtbo_size = count;
 284 +
 285 +       err = create_overlay(overlay, overlay->dtbo);
 286 +       if (err != 0)
 287 +               goto out_err;
 288 +
 289 +       return count;
 290 +
 291 +out_err:
 292 +       kfree(overlay->dtbo);
 293 +       overlay->dtbo = NULL;
 294 +       overlay->dtbo_size = 0;
 295 +
 296 +       return err;
 297 +}
 298 +
 299 +CONFIGFS_BIN_ATTR(cfs_overlay_item_, dtbo, NULL, SZ_1M);
 300 +
 301 +static struct configfs_bin_attribute *cfs_overlay_bin_attrs[] = {
 302 +       &cfs_overlay_item_attr_dtbo,
 303 +       NULL,
 304 +};
 305 +
 306 +static void cfs_overlay_release(struct config_item *item)
 307 +{
 308 +       struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
 309 +
 310 +       if (overlay->ov_id >= 0)
 311 +               of_overlay_destroy(overlay->ov_id);
 312 +       if (overlay->fw)
 313 +               release_firmware(overlay->fw);
 314 +       /* kfree with NULL is safe */
 315 +       kfree(overlay->dtbo);
 316 +       kfree(overlay);
 317 +}
 318 +
 319 +static struct configfs_item_operations cfs_overlay_item_ops = {
 320 +       .release        = cfs_overlay_release,
 321 +};
 322 +
 323 +static struct config_item_type cfs_overlay_type = {
 324 +       .ct_item_ops    = &cfs_overlay_item_ops,
 325 +       .ct_attrs       = cfs_overlay_attrs,
 326 +       .ct_bin_attrs   = cfs_overlay_bin_attrs,
 327 +       .ct_owner       = THIS_MODULE,
 328 +};
 329 +
 330 +static struct config_item *cfs_overlay_group_make_item(
 331 +               struct config_group *group, const char *name)
 332 +{
 333 +       struct cfs_overlay_item *overlay;
 334 +
 335 +       overlay = kzalloc(sizeof(*overlay), GFP_KERNEL);
 336 +       if (!overlay)
 337 +               return ERR_PTR(-ENOMEM);
 338 +       overlay->ov_id = -1;
 339 +
 340 +       config_item_init_type_name(&overlay->item, name, &cfs_overlay_type);
 341 +       return &overlay->item;
 342 +}
 343 +
 344 +static void cfs_overlay_group_drop_item(struct config_group *group,
 345 +               struct config_item *item)
 346 +{
 347 +       struct cfs_overlay_item *overlay = to_cfs_overlay_item(item);
 348 +
 349 +       config_item_put(&overlay->item);
 350 +}
 351 +
 352 +static struct configfs_group_operations overlays_ops = {
 353 +       .make_item      = cfs_overlay_group_make_item,
 354 +       .drop_item      = cfs_overlay_group_drop_item,
 355 +};
 356 +
 357 +static struct config_item_type overlays_type = {
 358 +       .ct_group_ops   = &overlays_ops,
 359 +       .ct_owner       = THIS_MODULE,
 360 +};
 361 +
 362 +static struct configfs_group_operations of_cfs_ops = {
 363 +       /* empty - we don't allow anything to be created */
 364 +};
 365 +
 366 +static struct config_item_type of_cfs_type = {
 367 +       .ct_group_ops   = &of_cfs_ops,
 368 +       .ct_owner       = THIS_MODULE,
 369 +};
 370 +
 371 +struct config_group of_cfs_overlay_group;
 372 +
 373 +struct config_group *of_cfs_def_groups[] = {
 374 +       &of_cfs_overlay_group,
 375 +       NULL
 376 +};
 377 +
 378 +static struct configfs_subsystem of_cfs_subsys = {
 379 +       .su_group = {
 380 +               .cg_item = {
 381 +                       .ci_namebuf = "device-tree",
 382 +                       .ci_type = &of_cfs_type,
 383 +               },
 384 +               .default_groups = of_cfs_def_groups,
 385 +       },
 386 +       .su_mutex = __MUTEX_INITIALIZER(of_cfs_subsys.su_mutex),
 387 +};
 388 +
 389 +static int __init of_cfs_init(void)
 390 +{
 391 +       int ret;
 392 +
 393 +       pr_info("%s\n", __func__);
 394 +
 395 +       config_group_init(&of_cfs_subsys.su_group);
 396 +       config_group_init_type_name(&of_cfs_overlay_group, "overlays",
 397 +                       &overlays_type);
 398 +
 399 +       ret = configfs_register_subsystem(&of_cfs_subsys);
 400 +       if (ret != 0) {
 401 +               pr_err("%s: failed to register subsys\n", __func__);
 402 +               goto out;
 403 +       }
 404 +       pr_info("%s: OK\n", __func__);
 405 +out:
 406 +       return ret;
 407 +}
 408 +late_initcall(of_cfs_init);