linux/drivers/gpu/drm/drm_dp_aux_dev.c
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   1/*
   2 * Copyright © 2015 Intel Corporation
   3 *
   4 * Permission is hereby granted, free of charge, to any person obtaining a
   5 * copy of this software and associated documentation files (the "Software"),
   6 * to deal in the Software without restriction, including without limitation
   7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8 * and/or sell copies of the Software, and to permit persons to whom the
   9 * Software is furnished to do so, subject to the following conditions:
  10 *
  11 * The above copyright notice and this permission notice (including the next
  12 * paragraph) shall be included in all copies or substantial portions of the
  13 * Software.
  14 *
  15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21 * IN THE SOFTWARE.
  22 *
  23 * Authors:
  24 *    Rafael Antognolli <rafael.antognolli@intel.com>
  25 *
  26 */
  27
  28#include <linux/device.h>
  29#include <linux/fs.h>
  30#include <linux/init.h>
  31#include <linux/kernel.h>
  32#include <linux/module.h>
  33#include <linux/sched/signal.h>
  34#include <linux/slab.h>
  35#include <linux/uaccess.h>
  36#include <linux/uio.h>
  37
  38#include <drm/drm_crtc.h>
  39#include <drm/drm_dp_helper.h>
  40#include <drm/drm_dp_mst_helper.h>
  41#include <drm/drm_print.h>
  42
  43#include "drm_crtc_helper_internal.h"
  44
  45struct drm_dp_aux_dev {
  46        unsigned index;
  47        struct drm_dp_aux *aux;
  48        struct device *dev;
  49        struct kref refcount;
  50        atomic_t usecount;
  51};
  52
  53#define DRM_AUX_MINORS  256
  54#define AUX_MAX_OFFSET  (1 << 20)
  55static DEFINE_IDR(aux_idr);
  56static DEFINE_MUTEX(aux_idr_mutex);
  57static struct class *drm_dp_aux_dev_class;
  58static int drm_dev_major = -1;
  59
  60static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
  61{
  62        struct drm_dp_aux_dev *aux_dev = NULL;
  63
  64        mutex_lock(&aux_idr_mutex);
  65        aux_dev = idr_find(&aux_idr, index);
  66        if (!kref_get_unless_zero(&aux_dev->refcount))
  67                aux_dev = NULL;
  68        mutex_unlock(&aux_idr_mutex);
  69
  70        return aux_dev;
  71}
  72
  73static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
  74{
  75        struct drm_dp_aux_dev *aux_dev;
  76        int index;
  77
  78        aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
  79        if (!aux_dev)
  80                return ERR_PTR(-ENOMEM);
  81        aux_dev->aux = aux;
  82        atomic_set(&aux_dev->usecount, 1);
  83        kref_init(&aux_dev->refcount);
  84
  85        mutex_lock(&aux_idr_mutex);
  86        index = idr_alloc(&aux_idr, aux_dev, 0, DRM_AUX_MINORS, GFP_KERNEL);
  87        mutex_unlock(&aux_idr_mutex);
  88        if (index < 0) {
  89                kfree(aux_dev);
  90                return ERR_PTR(index);
  91        }
  92        aux_dev->index = index;
  93
  94        return aux_dev;
  95}
  96
  97static void release_drm_dp_aux_dev(struct kref *ref)
  98{
  99        struct drm_dp_aux_dev *aux_dev =
 100                container_of(ref, struct drm_dp_aux_dev, refcount);
 101
 102        kfree(aux_dev);
 103}
 104
 105static ssize_t name_show(struct device *dev,
 106                         struct device_attribute *attr, char *buf)
 107{
 108        ssize_t res;
 109        struct drm_dp_aux_dev *aux_dev =
 110                drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
 111
 112        if (!aux_dev)
 113                return -ENODEV;
 114
 115        res = sprintf(buf, "%s\n", aux_dev->aux->name);
 116        kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 117
 118        return res;
 119}
 120static DEVICE_ATTR_RO(name);
 121
 122static struct attribute *drm_dp_aux_attrs[] = {
 123        &dev_attr_name.attr,
 124        NULL,
 125};
 126ATTRIBUTE_GROUPS(drm_dp_aux);
 127
 128static int auxdev_open(struct inode *inode, struct file *file)
 129{
 130        unsigned int minor = iminor(inode);
 131        struct drm_dp_aux_dev *aux_dev;
 132
 133        aux_dev = drm_dp_aux_dev_get_by_minor(minor);
 134        if (!aux_dev)
 135                return -ENODEV;
 136
 137        file->private_data = aux_dev;
 138        return 0;
 139}
 140
 141static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
 142{
 143        return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
 144}
 145
 146static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 147{
 148        struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
 149        loff_t pos = iocb->ki_pos;
 150        ssize_t res = 0;
 151
 152        if (!atomic_inc_not_zero(&aux_dev->usecount))
 153                return -ENODEV;
 154
 155        iov_iter_truncate(to, AUX_MAX_OFFSET - pos);
 156
 157        while (iov_iter_count(to)) {
 158                uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
 159                ssize_t todo = min(iov_iter_count(to), sizeof(buf));
 160
 161                if (signal_pending(current)) {
 162                        res = -ERESTARTSYS;
 163                        break;
 164                }
 165
 166                res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
 167
 168                if (res <= 0)
 169                        break;
 170
 171                if (copy_to_iter(buf, res, to) != res) {
 172                        res = -EFAULT;
 173                        break;
 174                }
 175
 176                pos += res;
 177        }
 178
 179        if (pos != iocb->ki_pos)
 180                res = pos - iocb->ki_pos;
 181        iocb->ki_pos = pos;
 182
 183        if (atomic_dec_and_test(&aux_dev->usecount))
 184                wake_up_var(&aux_dev->usecount);
 185
 186        return res;
 187}
 188
 189static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 190{
 191        struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
 192        loff_t pos = iocb->ki_pos;
 193        ssize_t res = 0;
 194
 195        if (!atomic_inc_not_zero(&aux_dev->usecount))
 196                return -ENODEV;
 197
 198        iov_iter_truncate(from, AUX_MAX_OFFSET - pos);
 199
 200        while (iov_iter_count(from)) {
 201                uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
 202                ssize_t todo = min(iov_iter_count(from), sizeof(buf));
 203
 204                if (signal_pending(current)) {
 205                        res = -ERESTARTSYS;
 206                        break;
 207                }
 208
 209                if (!copy_from_iter_full(buf, todo, from)) {
 210                        res = -EFAULT;
 211                        break;
 212                }
 213
 214                res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
 215
 216                if (res <= 0)
 217                        break;
 218
 219                pos += res;
 220        }
 221
 222        if (pos != iocb->ki_pos)
 223                res = pos - iocb->ki_pos;
 224        iocb->ki_pos = pos;
 225
 226        if (atomic_dec_and_test(&aux_dev->usecount))
 227                wake_up_var(&aux_dev->usecount);
 228
 229        return res;
 230}
 231
 232static int auxdev_release(struct inode *inode, struct file *file)
 233{
 234        struct drm_dp_aux_dev *aux_dev = file->private_data;
 235
 236        kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 237        return 0;
 238}
 239
 240static const struct file_operations auxdev_fops = {
 241        .owner          = THIS_MODULE,
 242        .llseek         = auxdev_llseek,
 243        .read_iter      = auxdev_read_iter,
 244        .write_iter     = auxdev_write_iter,
 245        .open           = auxdev_open,
 246        .release        = auxdev_release,
 247};
 248
 249#define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
 250
 251static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
 252{
 253        struct drm_dp_aux_dev *iter, *aux_dev = NULL;
 254        int id;
 255
 256        /* don't increase kref count here because this function should only be
 257         * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
 258         * least one reference - the one that drm_dp_aux_register_devnode
 259         * created
 260         */
 261        mutex_lock(&aux_idr_mutex);
 262        idr_for_each_entry(&aux_idr, iter, id) {
 263                if (iter->aux == aux) {
 264                        aux_dev = iter;
 265                        break;
 266                }
 267        }
 268        mutex_unlock(&aux_idr_mutex);
 269        return aux_dev;
 270}
 271
 272void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
 273{
 274        struct drm_dp_aux_dev *aux_dev;
 275        unsigned int minor;
 276
 277        aux_dev = drm_dp_aux_dev_get_by_aux(aux);
 278        if (!aux_dev) /* attach must have failed */
 279                return;
 280
 281        mutex_lock(&aux_idr_mutex);
 282        idr_remove(&aux_idr, aux_dev->index);
 283        mutex_unlock(&aux_idr_mutex);
 284
 285        atomic_dec(&aux_dev->usecount);
 286        wait_var_event(&aux_dev->usecount, !atomic_read(&aux_dev->usecount));
 287
 288        minor = aux_dev->index;
 289        if (aux_dev->dev)
 290                device_destroy(drm_dp_aux_dev_class,
 291                               MKDEV(drm_dev_major, minor));
 292
 293        DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
 294        kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 295}
 296
 297int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
 298{
 299        struct drm_dp_aux_dev *aux_dev;
 300        int res;
 301
 302        aux_dev = alloc_drm_dp_aux_dev(aux);
 303        if (IS_ERR(aux_dev))
 304                return PTR_ERR(aux_dev);
 305
 306        aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
 307                                     MKDEV(drm_dev_major, aux_dev->index), NULL,
 308                                     "drm_dp_aux%d", aux_dev->index);
 309        if (IS_ERR(aux_dev->dev)) {
 310                res = PTR_ERR(aux_dev->dev);
 311                aux_dev->dev = NULL;
 312                goto error;
 313        }
 314
 315        DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
 316                  aux->name, aux_dev->index);
 317        return 0;
 318error:
 319        drm_dp_aux_unregister_devnode(aux);
 320        return res;
 321}
 322
 323int drm_dp_aux_dev_init(void)
 324{
 325        int res;
 326
 327        drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
 328        if (IS_ERR(drm_dp_aux_dev_class)) {
 329                return PTR_ERR(drm_dp_aux_dev_class);
 330        }
 331        drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
 332
 333        res = register_chrdev(0, "aux", &auxdev_fops);
 334        if (res < 0)
 335                goto out;
 336        drm_dev_major = res;
 337
 338        return 0;
 339out:
 340        class_destroy(drm_dp_aux_dev_class);
 341        return res;
 342}
 343
 344void drm_dp_aux_dev_exit(void)
 345{
 346        unregister_chrdev(drm_dev_major, "aux");
 347        class_destroy(drm_dp_aux_dev_class);
 348}
 349