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         if (atomic_dec_and_test(&aux_dev->usecount))
 181                 wake_up_var(&aux_dev->usecount);
 182
 183         return res;
 184 }
 185
 186 static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 187 {
 188         struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
 189         loff_t pos = iocb->ki_pos;
 190         ssize_t res = 0;
 191
 192         if (!atomic_inc_not_zero(&aux_dev->usecount))
 193                 return -ENODEV;
 194
 195         iov_iter_truncate(from, AUX_MAX_OFFSET - pos);
 196
 197         while (iov_iter_count(from)) {
 198                 uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
 199                 ssize_t todo = min(iov_iter_count(from), sizeof(buf));
 200
 201                 if (signal_pending(current)) {
 202                         res = -ERESTARTSYS;
 203                         break;
 204                 }
 205
 206                 if (!copy_from_iter_full(buf, todo, from)) {
 207                         res = -EFAULT;
 208                         break;
 209                 }
 210
 211                 res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
 212                 if (res <= 0)
 213                         break;
 214
 215                 pos += res;
 216         }
 217
 218         if (pos != iocb->ki_pos)
 219                 res = pos - iocb->ki_pos;
 220         iocb->ki_pos = pos;
 221
 222         if (atomic_dec_and_test(&aux_dev->usecount))
 223                 wake_up_var(&aux_dev->usecount);
 224
 225         return res;
 226 }
 227
 228 static int auxdev_release(struct inode *inode, struct file *file)
 229 {
 230         struct drm_dp_aux_dev *aux_dev = file->private_data;
 231
 232         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 233         return 0;
 234 }
 235
 236 static const struct file_operations auxdev_fops = {
 237         .owner          = THIS_MODULE,
 238         .llseek         = auxdev_llseek,
 239         .read_iter      = auxdev_read_iter,
 240         .write_iter     = auxdev_write_iter,
 241         .open           = auxdev_open,
 242         .release        = auxdev_release,
 243 };
 244
 245 #define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
 246
 247 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
 248 {
 249         struct drm_dp_aux_dev *iter, *aux_dev = NULL;
 250         int id;
 251
 252         /* don't increase kref count here because this function should only be
 253          * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
 254          * least one reference - the one that drm_dp_aux_register_devnode
 255          * created
 256          */
 257         mutex_lock(&aux_idr_mutex);
 258         idr_for_each_entry(&aux_idr, iter, id) {
 259                 if (iter->aux == aux) {
 260                         aux_dev = iter;
 261                         break;
 262                 }
 263         }
 264         mutex_unlock(&aux_idr_mutex);
 265         return aux_dev;
 266 }
 267
 268 void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
 269 {
 270         struct drm_dp_aux_dev *aux_dev;
 271         unsigned int minor;
 272
 273         aux_dev = drm_dp_aux_dev_get_by_aux(aux);
 274         if (!aux_dev) /* attach must have failed */
 275                 return;
 276
 277         mutex_lock(&aux_idr_mutex);
 278         idr_remove(&aux_idr, aux_dev->index);
 279         mutex_unlock(&aux_idr_mutex);
 280
 281         atomic_dec(&aux_dev->usecount);
 282         wait_var_event(&aux_dev->usecount, !atomic_read(&aux_dev->usecount));
 283
 284         minor = aux_dev->index;
 285         if (aux_dev->dev)
 286                 device_destroy(drm_dp_aux_dev_class,
 287                                MKDEV(drm_dev_major, minor));
 288
 289         DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
 290         kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
 291 }
 292
 293 int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
 294 {
 295         struct drm_dp_aux_dev *aux_dev;
 296         int res;
 297
 298         aux_dev = alloc_drm_dp_aux_dev(aux);
 299         if (IS_ERR(aux_dev))
 300                 return PTR_ERR(aux_dev);
 301
 302         aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
 303                                      MKDEV(drm_dev_major, aux_dev->index), NULL,
 304                                      "drm_dp_aux%d", aux_dev->index);
 305         if (IS_ERR(aux_dev->dev)) {
 306                 res = PTR_ERR(aux_dev->dev);
 307                 aux_dev->dev = NULL;
 308                 goto error;
 309         }
 310
 311         DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
 312                   aux->name, aux_dev->index);
 313         return 0;
 314 error:
 315         drm_dp_aux_unregister_devnode(aux);
 316         return res;
 317 }
 318
 319 int drm_dp_aux_dev_init(void)
 320 {
 321         int res;
 322
 323         drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
 324         if (IS_ERR(drm_dp_aux_dev_class)) {
 325                 return PTR_ERR(drm_dp_aux_dev_class);
 326         }
 327         drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
 328
 329         res = register_chrdev(0, "aux", &auxdev_fops);
 330         if (res < 0)
 331                 goto out;
 332         drm_dev_major = res;
 333
 334         return 0;
 335 out:
 336         class_destroy(drm_dp_aux_dev_class);
 337         return res;
 338 }
 339
 340 void drm_dp_aux_dev_exit(void)
 341 {
 342         unregister_chrdev(drm_dev_major, "aux");
 343         class_destroy(drm_dp_aux_dev_class);
 344 }