drivers/gpu/drm/drm_dp_aux_dev.c

   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/slab.h>
  31 #include <linux/init.h>
  32 #include <linux/kernel.h>
  33 #include <linux/module.h>
  34 #include <linux/uaccess.h>
  35 #include <drm/drm_dp_helper.h>
  36 #include <drm/drm_crtc.h>
  37 #include <drm/drmP.h>
  38
  39 #include "drm_crtc_helper_internal.h"
  40
  41 struct drm_dp_aux_dev {
  42         unsigned index;
  43         struct drm_dp_aux *aux;
  44         struct device *dev;
  45         struct kref refcount;
  46         atomic_t usecount;
  47 };
  48
  49 #define DRM_AUX_MINORS  256
  50 #define AUX_MAX_OFFSET  (1 << 20)
  51 static DEFINE_IDR(aux_idr);
  52 static DEFINE_MUTEX(aux_idr_mutex);
  53 static struct class *drm_dp_aux_dev_class;
  54 static int drm_dev_major = -1;
  55
  56 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
  57 {
  58         struct drm_dp_aux_dev *aux_dev = NULL;
  59
  60         mutex_lock(&aux_idr_mutex);
  61         aux_dev = idr_find(&aux_idr, index);
  62         if (!kref_get_unless_zero(&aux_dev->refcount))
  63                 aux_dev = NULL;
  64         mutex_unlock(&aux_idr_mutex);
  65
  66         return aux_dev;
  67 }
  68
  69 static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
  70 {
  71         struct drm_dp_aux_dev *aux_dev;
  72         int index;
  73
  74         aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
  75         if (!aux_dev)
  76                 return ERR_PTR(-ENOMEM);
  77         aux_dev->aux = aux;
  78         atomic_set(&aux_dev->usecount, 1);
  79         kref_init(&aux_dev->refcount);
  80
  81         mutex_lock(&aux_idr_mutex);
  82         index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
  83                                  GFP_KERNEL);
  84         mutex_unlock(&aux_idr_mutex);
  85         if (index < 0) {
  86                 kfree(aux_dev);
  87                 return ERR_PTR(index);
  88         }
  89         aux_dev->index = index;
  90
  91         return aux_dev;
  92 }
  93
  94 static void release_drm_dp_aux_dev(struct kref *ref)
  95 {
  96         struct drm_dp_aux_dev *aux_dev =
  97                 container_of(ref, struct drm_dp_aux_dev, refcount);
  98
  99         kfree(aux_dev);
 100 }
 101
 102 static ssize_t name_show(struct device *dev,
 103                          struct device_attribute *attr, char *buf)
 104 {
 105         ssize_t res;
 106         struct drm_dp_aux_dev *aux_dev =
 107                 drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
 108
 109         if (!aux_dev)
 110                 return -ENODEV;
 111
 112         res = sprintf(buf, "%s\n", aux_dev->aux->name);
 113         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 114
 115         return res;
 116 }
 117 static DEVICE_ATTR_RO(name);
 118
 119 static struct attribute *drm_dp_aux_attrs[] = {
 120         &dev_attr_name.attr,
 121         NULL,
 122 };
 123 ATTRIBUTE_GROUPS(drm_dp_aux);
 124
 125 static int auxdev_open(struct inode *inode, struct file *file)
 126 {
 127         unsigned int minor = iminor(inode);
 128         struct drm_dp_aux_dev *aux_dev;
 129
 130         aux_dev = drm_dp_aux_dev_get_by_minor(minor);
 131         if (!aux_dev)
 132                 return -ENODEV;
 133
 134         file->private_data = aux_dev;
 135         return 0;
 136 }
 137
 138 static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
 139 {
 140         return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
 141 }
 142
 143 static ssize_t auxdev_read(struct file *file, char __user *buf, size_t count,
 144                            loff_t *offset)
 145 {
 146         size_t bytes_pending, num_bytes_processed = 0;
 147         struct drm_dp_aux_dev *aux_dev = file->private_data;
 148         ssize_t res = 0;
 149
 150         if (!atomic_inc_not_zero(&aux_dev->usecount))
 151                 return -ENODEV;
 152
 153         bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));
 154
 155         if (!access_ok(VERIFY_WRITE, buf, bytes_pending)) {
 156                 res = -EFAULT;
 157                 goto out;
 158         }
 159
 160         while (bytes_pending > 0) {
 161                 uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
 162                 ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
 163
 164                 if (signal_pending(current)) {
 165                         res = num_bytes_processed ?
 166                                 num_bytes_processed : -ERESTARTSYS;
 167                         goto out;
 168                 }
 169
 170                 res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
 171                 if (res <= 0) {
 172                         res = num_bytes_processed ? num_bytes_processed : res;
 173                         goto out;
 174                 }
 175                 if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
 176                         res = num_bytes_processed ?
 177                                 num_bytes_processed : -EFAULT;
 178                         goto out;
 179                 }
 180                 bytes_pending -= res;
 181                 *offset += res;
 182                 num_bytes_processed += res;
 183                 res = num_bytes_processed;
 184         }
 185
 186 out:
 187         atomic_dec(&aux_dev->usecount);
 188         wake_up_atomic_t(&aux_dev->usecount);
 189         return res;
 190 }
 191
 192 static ssize_t auxdev_write(struct file *file, const char __user *buf,
 193                             size_t count, loff_t *offset)
 194 {
 195         size_t bytes_pending, num_bytes_processed = 0;
 196         struct drm_dp_aux_dev *aux_dev = file->private_data;
 197         ssize_t res = 0;
 198
 199         if (!atomic_inc_not_zero(&aux_dev->usecount))
 200                 return -ENODEV;
 201
 202         bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);
 203
 204         if (!access_ok(VERIFY_READ, buf, bytes_pending)) {
 205                 res = -EFAULT;
 206                 goto out;
 207         }
 208
 209         while (bytes_pending > 0) {
 210                 uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
 211                 ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
 212
 213                 if (signal_pending(current)) {
 214                         res = num_bytes_processed ?
 215                                 num_bytes_processed : -ERESTARTSYS;
 216                         goto out;
 217                 }
 218
 219                 if (__copy_from_user(localbuf,
 220                                      buf + num_bytes_processed, todo)) {
 221                         res = num_bytes_processed ?
 222                                 num_bytes_processed : -EFAULT;
 223                         goto out;
 224                 }
 225
 226                 res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
 227                 if (res <= 0) {
 228                         res = num_bytes_processed ? num_bytes_processed : res;
 229                         goto out;
 230                 }
 231                 bytes_pending -= res;
 232                 *offset += res;
 233                 num_bytes_processed += res;
 234                 res = num_bytes_processed;
 235         }
 236
 237 out:
 238         atomic_dec(&aux_dev->usecount);
 239         wake_up_atomic_t(&aux_dev->usecount);
 240         return res;
 241 }
 242
 243 static int auxdev_release(struct inode *inode, struct file *file)
 244 {
 245         struct drm_dp_aux_dev *aux_dev = file->private_data;
 246
 247         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 248         return 0;
 249 }
 250
 251 static const struct file_operations auxdev_fops = {
 252         .owner          = THIS_MODULE,
 253         .llseek         = auxdev_llseek,
 254         .read           = auxdev_read,
 255         .write          = auxdev_write,
 256         .open           = auxdev_open,
 257         .release        = auxdev_release,
 258 };
 259
 260 #define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
 261
 262 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
 263 {
 264         struct drm_dp_aux_dev *iter, *aux_dev = NULL;
 265         int id;
 266
 267         /* don't increase kref count here because this function should only be
 268          * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
 269          * least one reference - the one that drm_dp_aux_register_devnode
 270          * created
 271          */
 272         mutex_lock(&aux_idr_mutex);
 273         idr_for_each_entry(&aux_idr, iter, id) {
 274                 if (iter->aux == aux) {
 275                         aux_dev = iter;
 276                         break;
 277                 }
 278         }
 279         mutex_unlock(&aux_idr_mutex);
 280         return aux_dev;
 281 }
 282
 283 static int auxdev_wait_atomic_t(atomic_t *p)
 284 {
 285         schedule();
 286         return 0;
 287 }
 288
 289 void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
 290 {
 291         struct drm_dp_aux_dev *aux_dev;
 292         unsigned int minor;
 293
 294         aux_dev = drm_dp_aux_dev_get_by_aux(aux);
 295         if (!aux_dev) /* attach must have failed */
 296                 return;
 297
 298         mutex_lock(&aux_idr_mutex);
 299         idr_remove(&aux_idr, aux_dev->index);
 300         mutex_unlock(&aux_idr_mutex);
 301
 302         atomic_dec(&aux_dev->usecount);
 303         wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
 304                          TASK_UNINTERRUPTIBLE);
 305
 306         minor = aux_dev->index;
 307         if (aux_dev->dev)
 308                 device_destroy(drm_dp_aux_dev_class,
 309                                MKDEV(drm_dev_major, minor));
 310
 311         DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
 312         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 313 }
 314
 315 int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
 316 {
 317         struct drm_dp_aux_dev *aux_dev;
 318         int res;
 319
 320         aux_dev = alloc_drm_dp_aux_dev(aux);
 321         if (IS_ERR(aux_dev))
 322                 return PTR_ERR(aux_dev);
 323
 324         aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
 325                                      MKDEV(drm_dev_major, aux_dev->index), NULL,
 326                                      "drm_dp_aux%d", aux_dev->index);
 327         if (IS_ERR(aux_dev->dev)) {
 328                 res = PTR_ERR(aux_dev->dev);
 329                 aux_dev->dev = NULL;
 330                 goto error;
 331         }
 332
 333         DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
 334                   aux->name, aux_dev->index);
 335         return 0;
 336 error:
 337         drm_dp_aux_unregister_devnode(aux);
 338         return res;
 339 }
 340
 341 int drm_dp_aux_dev_init(void)
 342 {
 343         int res;
 344
 345         drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
 346         if (IS_ERR(drm_dp_aux_dev_class)) {
 347                 return PTR_ERR(drm_dp_aux_dev_class);
 348         }
 349         drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
 350
 351         res = register_chrdev(0, "aux", &auxdev_fops);
 352         if (res < 0)
 353                 goto out;
 354         drm_dev_major = res;
 355
 356         return 0;
 357 out:
 358         class_destroy(drm_dp_aux_dev_class);
 359         return res;
 360 }
 361
 362 void drm_dp_aux_dev_exit(void)
 363 {
 364         unregister_chrdev(drm_dev_major, "aux");
 365         class_destroy(drm_dp_aux_dev_class);
 366 }