drm/display/drm_dp_aux_dev.c

0001 /*
0002  * Copyright © 2015 Intel Corporation
0003  *
0004  * Permission is hereby granted, free of charge, to any person obtaining a
0005  * copy of this software and associated documentation files (the "Software"),
0006  * to deal in the Software without restriction, including without limitation
0007  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
0008  * and/or sell copies of the Software, and to permit persons to whom the
0009  * Software is furnished to do so, subject to the following conditions:
0010  *
0011  * The above copyright notice and this permission notice (including the next
0012  * paragraph) shall be included in all copies or substantial portions of the
0013  * Software.
0014  *
0015  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
0016  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
0017  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
0018  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
0019  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
0020  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
0021  * IN THE SOFTWARE.
0022  *
0023  * Authors:
0024  *    Rafael Antognolli <rafael.antognolli@intel.com>
0025  *
0026  */
0027
0028 #include <linux/device.h>
0029 #include <linux/fs.h>
0030 #include <linux/init.h>
0031 #include <linux/kernel.h>
0032 #include <linux/module.h>
0033 #include <linux/sched/signal.h>
0034 #include <linux/slab.h>
0035 #include <linux/uaccess.h>
0036 #include <linux/uio.h>
0037
0038 #include <drm/display/drm_dp_helper.h>
0039 #include <drm/display/drm_dp_mst_helper.h>
0040 #include <drm/drm_crtc.h>
0041 #include <drm/drm_print.h>
0042
0043 #include "drm_dp_helper_internal.h"
0044
0045 struct drm_dp_aux_dev {
0046     unsigned index;
0047     struct drm_dp_aux *aux;
0048     struct device *dev;
0049     struct kref refcount;
0050     atomic_t usecount;
0051 };
0052
0053 #define DRM_AUX_MINORS  256
0054 #define AUX_MAX_OFFSET  (1 << 20)
0055 static DEFINE_IDR(aux_idr);
0056 static DEFINE_MUTEX(aux_idr_mutex);
0057 static struct class *drm_dp_aux_dev_class;
0058 static int drm_dev_major = -1;
0059
0060 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_minor(unsigned index)
0061 {
0062     struct drm_dp_aux_dev *aux_dev = NULL;
0063
0064     mutex_lock(&aux_idr_mutex);
0065     aux_dev = idr_find(&aux_idr, index);
0066     if (aux_dev && !kref_get_unless_zero(&aux_dev->refcount))
0067         aux_dev = NULL;
0068     mutex_unlock(&aux_idr_mutex);
0069
0070     return aux_dev;
0071 }
0072
0073 static struct drm_dp_aux_dev *alloc_drm_dp_aux_dev(struct drm_dp_aux *aux)
0074 {
0075     struct drm_dp_aux_dev *aux_dev;
0076     int index;
0077
0078     aux_dev = kzalloc(sizeof(*aux_dev), GFP_KERNEL);
0079     if (!aux_dev)
0080         return ERR_PTR(-ENOMEM);
0081     aux_dev->aux = aux;
0082     atomic_set(&aux_dev->usecount, 1);
0083     kref_init(&aux_dev->refcount);
0084
0085     mutex_lock(&aux_idr_mutex);
0086     index = idr_alloc(&aux_idr, aux_dev, 0, DRM_AUX_MINORS, GFP_KERNEL);
0087     mutex_unlock(&aux_idr_mutex);
0088     if (index < 0) {
0089         kfree(aux_dev);
0090         return ERR_PTR(index);
0091     }
0092     aux_dev->index = index;
0093
0094     return aux_dev;
0095 }
0096
0097 static void release_drm_dp_aux_dev(struct kref *ref)
0098 {
0099     struct drm_dp_aux_dev *aux_dev =
0100         container_of(ref, struct drm_dp_aux_dev, refcount);
0101
0102     kfree(aux_dev);
0103 }
0104
0105 static ssize_t name_show(struct device *dev,
0106              struct device_attribute *attr, char *buf)
0107 {
0108     ssize_t res;
0109     struct drm_dp_aux_dev *aux_dev =
0110         drm_dp_aux_dev_get_by_minor(MINOR(dev->devt));
0111
0112     if (!aux_dev)
0113         return -ENODEV;
0114
0115     res = sprintf(buf, "%s\n", aux_dev->aux->name);
0116     kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
0117
0118     return res;
0119 }
0120 static DEVICE_ATTR_RO(name);
0121
0122 static struct attribute *drm_dp_aux_attrs[] = {
0123     &dev_attr_name.attr,
0124     NULL,
0125 };
0126 ATTRIBUTE_GROUPS(drm_dp_aux);
0127
0128 static int auxdev_open(struct inode *inode, struct file *file)
0129 {
0130     unsigned int minor = iminor(inode);
0131     struct drm_dp_aux_dev *aux_dev;
0132
0133     aux_dev = drm_dp_aux_dev_get_by_minor(minor);
0134     if (!aux_dev)
0135         return -ENODEV;
0136
0137     file->private_data = aux_dev;
0138     return 0;
0139 }
0140
0141 static loff_t auxdev_llseek(struct file *file, loff_t offset, int whence)
0142 {
0143     return fixed_size_llseek(file, offset, whence, AUX_MAX_OFFSET);
0144 }
0145
0146 static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
0147 {
0148     struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
0149     loff_t pos = iocb->ki_pos;
0150     ssize_t res = 0;
0151
0152     if (!atomic_inc_not_zero(&aux_dev->usecount))
0153         return -ENODEV;
0154
0155     iov_iter_truncate(to, AUX_MAX_OFFSET - pos);
0156
0157     while (iov_iter_count(to)) {
0158         uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
0159         ssize_t todo = min(iov_iter_count(to), sizeof(buf));
0160
0161         if (signal_pending(current)) {
0162             res = -ERESTARTSYS;
0163             break;
0164         }
0165
0166         res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
0167
0168         if (res <= 0)
0169             break;
0170
0171         if (copy_to_iter(buf, res, to) != res) {
0172             res = -EFAULT;
0173             break;
0174         }
0175
0176         pos += res;
0177     }
0178
0179     if (pos != iocb->ki_pos)
0180         res = pos - iocb->ki_pos;
0181     iocb->ki_pos = pos;
0182
0183     if (atomic_dec_and_test(&aux_dev->usecount))
0184         wake_up_var(&aux_dev->usecount);
0185
0186     return res;
0187 }
0188
0189 static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
0190 {
0191     struct drm_dp_aux_dev *aux_dev = iocb->ki_filp->private_data;
0192     loff_t pos = iocb->ki_pos;
0193     ssize_t res = 0;
0194
0195     if (!atomic_inc_not_zero(&aux_dev->usecount))
0196         return -ENODEV;
0197
0198     iov_iter_truncate(from, AUX_MAX_OFFSET - pos);
0199
0200     while (iov_iter_count(from)) {
0201         uint8_t buf[DP_AUX_MAX_PAYLOAD_BYTES];
0202         ssize_t todo = min(iov_iter_count(from), sizeof(buf));
0203
0204         if (signal_pending(current)) {
0205             res = -ERESTARTSYS;
0206             break;
0207         }
0208
0209         if (!copy_from_iter_full(buf, todo, from)) {
0210             res = -EFAULT;
0211             break;
0212         }
0213
0214         res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
0215
0216         if (res <= 0)
0217             break;
0218
0219         pos += res;
0220     }
0221
0222     if (pos != iocb->ki_pos)
0223         res = pos - iocb->ki_pos;
0224     iocb->ki_pos = pos;
0225
0226     if (atomic_dec_and_test(&aux_dev->usecount))
0227         wake_up_var(&aux_dev->usecount);
0228
0229     return res;
0230 }
0231
0232 static int auxdev_release(struct inode *inode, struct file *file)
0233 {
0234     struct drm_dp_aux_dev *aux_dev = file->private_data;
0235
0236     kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
0237     return 0;
0238 }
0239
0240 static const struct file_operations auxdev_fops = {
0241     .owner      = THIS_MODULE,
0242     .llseek     = auxdev_llseek,
0243     .read_iter  = auxdev_read_iter,
0244     .write_iter = auxdev_write_iter,
0245     .open       = auxdev_open,
0246     .release    = auxdev_release,
0247 };
0248
0249 #define to_auxdev(d) container_of(d, struct drm_dp_aux_dev, aux)
0250
0251 static struct drm_dp_aux_dev *drm_dp_aux_dev_get_by_aux(struct drm_dp_aux *aux)
0252 {
0253     struct drm_dp_aux_dev *iter, *aux_dev = NULL;
0254     int id;
0255
0256     /* don't increase kref count here because this function should only be
0257      * used by drm_dp_aux_unregister_devnode. Thus, it will always have at
0258      * least one reference - the one that drm_dp_aux_register_devnode
0259      * created
0260      */
0261     mutex_lock(&aux_idr_mutex);
0262     idr_for_each_entry(&aux_idr, iter, id) {
0263         if (iter->aux == aux) {
0264             aux_dev = iter;
0265             break;
0266         }
0267     }
0268     mutex_unlock(&aux_idr_mutex);
0269     return aux_dev;
0270 }
0271
0272 void drm_dp_aux_unregister_devnode(struct drm_dp_aux *aux)
0273 {
0274     struct drm_dp_aux_dev *aux_dev;
0275     unsigned int minor;
0276
0277     aux_dev = drm_dp_aux_dev_get_by_aux(aux);
0278     if (!aux_dev) /* attach must have failed */
0279         return;
0280
0281     /*
0282      * As some AUX adapters may exist as platform devices which outlive their respective DRM
0283      * devices, we clear drm_dev to ensure that we never accidentally reference a stale pointer
0284      */
0285     aux->drm_dev = NULL;
0286
0287     mutex_lock(&aux_idr_mutex);
0288     idr_remove(&aux_idr, aux_dev->index);
0289     mutex_unlock(&aux_idr_mutex);
0290
0291     atomic_dec(&aux_dev->usecount);
0292     wait_var_event(&aux_dev->usecount, !atomic_read(&aux_dev->usecount));
0293
0294     minor = aux_dev->index;
0295     if (aux_dev->dev)
0296         device_destroy(drm_dp_aux_dev_class,
0297                    MKDEV(drm_dev_major, minor));
0298
0299     DRM_DEBUG("drm_dp_aux_dev: aux [%s] unregistering\n", aux->name);
0300     kref_put(&aux_dev->refcount, release_drm_dp_aux_dev);
0301 }
0302
0303 int drm_dp_aux_register_devnode(struct drm_dp_aux *aux)
0304 {
0305     struct drm_dp_aux_dev *aux_dev;
0306     int res;
0307
0308     aux_dev = alloc_drm_dp_aux_dev(aux);
0309     if (IS_ERR(aux_dev))
0310         return PTR_ERR(aux_dev);
0311
0312     aux_dev->dev = device_create(drm_dp_aux_dev_class, aux->dev,
0313                      MKDEV(drm_dev_major, aux_dev->index), NULL,
0314                      "drm_dp_aux%d", aux_dev->index);
0315     if (IS_ERR(aux_dev->dev)) {
0316         res = PTR_ERR(aux_dev->dev);
0317         aux_dev->dev = NULL;
0318         goto error;
0319     }
0320
0321     DRM_DEBUG("drm_dp_aux_dev: aux [%s] registered as minor %d\n",
0322           aux->name, aux_dev->index);
0323     return 0;
0324 error:
0325     drm_dp_aux_unregister_devnode(aux);
0326     return res;
0327 }
0328
0329 int drm_dp_aux_dev_init(void)
0330 {
0331     int res;
0332
0333     drm_dp_aux_dev_class = class_create(THIS_MODULE, "drm_dp_aux_dev");
0334     if (IS_ERR(drm_dp_aux_dev_class)) {
0335         return PTR_ERR(drm_dp_aux_dev_class);
0336     }
0337     drm_dp_aux_dev_class->dev_groups = drm_dp_aux_groups;
0338
0339     res = register_chrdev(0, "aux", &auxdev_fops);
0340     if (res < 0)
0341         goto out;
0342     drm_dev_major = res;
0343
0344     return 0;
0345 out:
0346     class_destroy(drm_dp_aux_dev_class);
0347     return res;
0348 }
0349
0350 void drm_dp_aux_dev_exit(void)
0351 {
0352     unregister_chrdev(drm_dev_major, "aux");
0353     class_destroy(drm_dp_aux_dev_class);
0354 }