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 struct drm_dp_aux_dev {
  40         unsigned index;
  41         struct drm_dp_aux *aux;
  42         struct device *dev;
  43         struct kref refcount;
  44         atomic_t usecount;
  45 };
  46
  47 #define DRM_AUX_MINORS  256
  48 #define AUX_MAX_OFFSET  (1 << 20)
  49 static DEFINE_IDR(aux_idr);
  50 static DEFINE_MUTEX(aux_idr_mutex);
  51 static struct class *drm_dp_aux_dev_class;
  52 static int drm_dev_major = -1;
  53
  54 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
  55 {
  56         struct drm_dp_aux_dev *aux_dev = NULL;
  57
  58         mutex_lock(&aux_idr_mutex);
  59         aux_dev = idr_find(&aux_idr, index);
  60         if (!kref_get_unless_zero(&aux_dev->refcount))
  61                 aux_dev = NULL;
  62         mutex_unlock(&aux_idr_mutex);
  63
  64         return aux_dev;
  65 }
  66
  67 static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
  68 {
  69         struct drm_dp_aux_dev *aux_dev;
  70         int index;
  71
  72         aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
  73         if (!aux_dev)
  74                 return ERR_PTR(-ENOMEM);
  75         aux_dev->aux = aux;
  76         atomic_set(&aux_dev->usecount, 1);
  77         kref_init(&aux_dev->refcount);
  78
  79         mutex_lock(&aux_idr_mutex);
  80         index = idr_alloc_cyclic(&aux_idr, aux_dev, 0, DRM_AUX_MINORS,
  81                                  GFP_KERNEL);
  82         mutex_unlock(&aux_idr_mutex);
  83         if (index < 0) {
  84                 kfree(aux_dev);
  85                 return ERR_PTR(index);
  86         }
  87         aux_dev->index = index;
  88
  89         return aux_dev;
  90 }
  91
  92 static void release_drm_dp_aux_dev(struct kref *ref)
  93 {
  94         struct drm_dp_aux_dev *aux_dev =
  95                 container_of(ref, struct drm_dp_aux_dev, refcount);
  96
  97         kfree(aux_dev);
  98 }
  99
 100 static ssize_t name_show(struct device *dev,
 101                          struct device_attribute *attr, char *buf)
 102 {
 103         ssize_t res;
 104         struct drm_dp_aux_dev *aux_dev =
 105                 drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
 106
 107         if (!aux_dev)
 108                 return -ENODEV;
 109
 110         res = sprintf(buf, "%s\n", aux_dev->aux->name);
 111         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 112
 113         return res;
 114 }
 115 static DEVICE_ATTR_RO(name);
 116
 117 static struct attribute *drm_dp_aux_attrs[] = {
 118         &dev_attr_name.attr,
 119         NULL,
 120 };
 121 ATTRIBUTE_GROUPS(drm_dp_aux);
 122
 123 static int auxdev_open(struct inode *inode, struct file *file)
 124 {
 125         unsigned int minor = iminor(inode);
 126         struct drm_dp_aux_dev *aux_dev;
 127
 128         aux_dev = drm_dp_aux_dev_get_by_minor(minor);
 129         if (!aux_dev)
 130                 return -ENODEV;
 131
 132         file->private_data = aux_dev;
 133         return 0;
 134 }
 135
 136 static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
 137 {
 138         return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
 139 }
 140
 141 static ssize_t auxdev_read(struct file *file, char __user *buf, size_t count,
 142                            loff_t *offset)
 143 {
 144         size_t bytes_pending, num_bytes_processed = 0;
 145         struct drm_dp_aux_dev *aux_dev = file->private_data;
 146         ssize_t res = 0;
 147
 148         if (!atomic_inc_not_zero(&aux_dev->usecount))
 149                 return -ENODEV;
 150
 151         bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - (*offset));
 152
 153         if (!access_ok(VERIFY_WRITE, buf, bytes_pending)) {
 154                 res = -EFAULT;
 155                 goto out;
 156         }
 157
 158         while (bytes_pending > 0) {
 159                 uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
 160                 ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
 161
 162                 res = drm_dp_dpcd_read(aux_dev->aux, *offset, localbuf, todo);
 163                 if (res <= 0) {
 164                         res = num_bytes_processed ? num_bytes_processed : res;
 165                         goto out;
 166                 }
 167                 if (__copy_to_user(buf + num_bytes_processed, localbuf, res)) {
 168                         res = num_bytes_processed ?
 169                                 num_bytes_processed : -EFAULT;
 170                         goto out;
 171                 }
 172                 bytes_pending -= res;
 173                 *offset += res;
 174                 num_bytes_processed += res;
 175                 res = num_bytes_processed;
 176         }
 177
 178 out:
 179         atomic_dec(&aux_dev->usecount);
 180         wake_up_atomic_t(&aux_dev->usecount);
 181         return res;
 182 }
 183
 184 static ssize_t auxdev_write(struct file *file, const char __user *buf,
 185                             size_t count, loff_t *offset)
 186 {
 187         size_t bytes_pending, num_bytes_processed = 0;
 188         struct drm_dp_aux_dev *aux_dev = file->private_data;
 189         ssize_t res = 0;
 190
 191         if (!atomic_inc_not_zero(&aux_dev->usecount))
 192                 return -ENODEV;
 193
 194         bytes_pending = min((loff_t)count, AUX_MAX_OFFSET - *offset);
 195
 196         if (!access_ok(VERIFY_READ, buf, bytes_pending)) {
 197                 res = -EFAULT;
 198                 goto out;
 199         }
 200
 201         while (bytes_pending > 0) {
 202                 uint8_t localbuf[DP_AUX_MAX_PAYLOAD_BYTES];
 203                 ssize_t todo = min_t(size_t, bytes_pending, sizeof(localbuf));
 204
 205                 if (__copy_from_user(localbuf,
 206                                      buf + num_bytes_processed, todo)) {
 207                         res = num_bytes_processed ?
 208                                 num_bytes_processed : -EFAULT;
 209                         goto out;
 210                 }
 211
 212                 res = drm_dp_dpcd_write(aux_dev->aux, *offset, localbuf, todo);
 213                 if (res <= 0) {
 214                         res = num_bytes_processed ? num_bytes_processed : res;
 215                         goto out;
 216                 }
 217                 bytes_pending -= res;
 218                 *offset += res;
 219                 num_bytes_processed += res;
 220                 res = num_bytes_processed;
 221         }
 222
 223 out:
 224         atomic_dec(&aux_dev->usecount);
 225         wake_up_atomic_t(&aux_dev->usecount);
 226         return res;
 227 }
 228
 229 static int auxdev_release(struct inode *inode, struct file *file)
 230 {
 231         struct drm_dp_aux_dev *aux_dev = file->private_data;
 232
 233         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 234         return 0;
 235 }
 236
 237 static const struct file_operations auxdev_fops = {
 238         .owner          = THIS_MODULE,
 239         .llseek         = auxdev_llseek,
 240         .read           = auxdev_read,
 241         .write          = auxdev_write,
 242         .open           = auxdev_open,
 243         .release        = auxdev_release,
 244 };
 245
 246 #define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
 247
 248 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
 249 {
 250         struct drm_dp_aux_dev *iter, *aux_dev = NULL;
 251         int id;
 252
 253         /* don't increase kref count here because this function should only be
 254          * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
 255          * least one reference - the one that drm_dp_aux_register_devnode
 256          * created
 257          */
 258         mutex_lock(&aux_idr_mutex);
 259         idr_for_each_entry(&aux_idr, iter, id) {
 260                 if (iter->aux == aux) {
 261                         aux_dev = iter;
 262                         break;
 263                 }
 264         }
 265         mutex_unlock(&aux_idr_mutex);
 266         return aux_dev;
 267 }
 268
 269 static int auxdev_wait_atomic_t(atomic_t *p)
 270 {
 271         schedule();
 272         return 0;
 273 }
 274 /**
 275  * drm_dp_aux_unregister_devnode() - unregister a devnode for this aux channel
 276  * @aux: DisplayPort AUX channel
 277  *
 278  * Returns 0 on success or a negative error code on failure.
 279  */
 280 void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
 281 {
 282         struct drm_dp_aux_dev *aux_dev;
 283         unsigned int minor;
 284
 285         aux_dev = drm_dp_aux_dev_get_by_aux(aux);
 286         if (!aux_dev) /* attach must have failed */
 287                 return;
 288
 289         mutex_lock(&aux_idr_mutex);
 290         idr_remove(&aux_idr, aux_dev->index);
 291         mutex_unlock(&aux_idr_mutex);
 292
 293         atomic_dec(&aux_dev->usecount);
 294         wait_on_atomic_t(&aux_dev->usecount, auxdev_wait_atomic_t,
 295                          TASK_UNINTERRUPTIBLE);
 296
 297         minor = aux_dev->index;
 298         if (aux_dev->dev)
 299                 device_destroy(drm_dp_aux_dev_class,
 300                                MKDEV(drm_dev_major, minor));
 301
 302         DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
 303         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 304 }
 305 EXPORT_SYMBOL(drm_dp_aux_unregister_devnode);
 306
 307 /**
 308  * drm_dp_aux_register_devnode() - register a devnode for this aux channel
 309  * @aux: DisplayPort AUX channel
 310  *
 311  * Returns 0 on success or a negative error code on failure.
 312  */
 313 int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
 314 {
 315         struct drm_dp_aux_dev *aux_dev;
 316         int res;
 317
 318         aux_dev = alloc_drm_dp_aux_dev(aux);
 319         if (IS_ERR(aux_dev))
 320                 return PTR_ERR(aux_dev);
 321
 322         aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
 323                                      MKDEV(drm_dev_major, aux_dev->index), NULL,
 324                                      "drm_dp_aux%d", aux_dev->index);
 325         if (IS_ERR(aux_dev->dev)) {
 326                 res = PTR_ERR(aux_dev->dev);
 327                 aux_dev->dev = NULL;
 328                 goto error;
 329         }
 330
 331         DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
 332                   aux->name, aux_dev->index);
 333         return 0;
 334 error:
 335         drm_dp_aux_unregister_devnode(aux);
 336         return res;
 337 }
 338 EXPORT_SYMBOL(drm_dp_aux_register_devnode);
 339
 340 int drm_dp_aux_dev_init(void)
 341 {
 342         int res;
 343
 344         drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
 345         if (IS_ERR(drm_dp_aux_dev_class)) {
 346                 res = PTR_ERR(drm_dp_aux_dev_class);
 347                 goto out;
 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 EXPORT_SYMBOL(drm_dp_aux_dev_init);
 362
 363 void drm_dp_aux_dev_exit(void)
 364 {
 365         unregister_chrdev(drm_dev_major, "aux");
 366         class_destroy(drm_dp_aux_dev_class);
 367 }
 368 EXPORT_SYMBOL(drm_dp_aux_dev_exit);