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