drivers/media/v4l2-core/v4l2-clk.c

   1 /*
   2  * V4L2 clock service
   3  *
   4  * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/atomic.h>
  12 #include <linux/device.h>
  13 #include <linux/errno.h>
  14 #include <linux/list.h>
  15 #include <linux/module.h>
  16 #include <linux/mutex.h>
  17 #include <linux/slab.h>
  18 #include <linux/string.h>
  19
  20 #include <media/v4l2-clk.h>
  21 #include <media/v4l2-subdev.h>
  22
  23 static DEFINE_MUTEX(clk_lock);
  24 static LIST_HEAD(clk_list);
  25
  26 static struct v4l2_clk *v4l2_clk_find(const char *dev_id, const char *id)
  27 {
  28         struct v4l2_clk *clk;
  29
  30         list_for_each_entry(clk, &clk_list, list) {
  31                 if (strcmp(dev_id, clk->dev_id))
  32                         continue;
  33
  34                 if (!id || !clk->id || !strcmp(clk->id, id))
  35                         return clk;
  36         }
  37
  38         return ERR_PTR(-ENODEV);
  39 }
  40
  41 struct v4l2_clk *v4l2_clk_get(struct device *dev, const char *id)
  42 {
  43         struct v4l2_clk *clk;
  44
  45         mutex_lock(&clk_lock);
  46         clk = v4l2_clk_find(dev_name(dev), id);
  47
  48         if (!IS_ERR(clk))
  49                 atomic_inc(&clk->use_count);
  50         mutex_unlock(&clk_lock);
  51
  52         return clk;
  53 }
  54 EXPORT_SYMBOL(v4l2_clk_get);
  55
  56 void v4l2_clk_put(struct v4l2_clk *clk)
  57 {
  58         struct v4l2_clk *tmp;
  59
  60         if (IS_ERR(clk))
  61                 return;
  62
  63         mutex_lock(&clk_lock);
  64
  65         list_for_each_entry(tmp, &clk_list, list)
  66                 if (tmp == clk)
  67                         atomic_dec(&clk->use_count);
  68
  69         mutex_unlock(&clk_lock);
  70 }
  71 EXPORT_SYMBOL(v4l2_clk_put);
  72
  73 static int v4l2_clk_lock_driver(struct v4l2_clk *clk)
  74 {
  75         struct v4l2_clk *tmp;
  76         int ret = -ENODEV;
  77
  78         mutex_lock(&clk_lock);
  79
  80         list_for_each_entry(tmp, &clk_list, list)
  81                 if (tmp == clk) {
  82                         ret = !try_module_get(clk->ops->owner);
  83                         if (ret)
  84                                 ret = -EFAULT;
  85                         break;
  86                 }
  87
  88         mutex_unlock(&clk_lock);
  89
  90         return ret;
  91 }
  92
  93 static void v4l2_clk_unlock_driver(struct v4l2_clk *clk)
  94 {
  95         module_put(clk->ops->owner);
  96 }
  97
  98 int v4l2_clk_enable(struct v4l2_clk *clk)
  99 {
 100         int ret = v4l2_clk_lock_driver(clk);
 101
 102         if (ret < 0)
 103                 return ret;
 104
 105         mutex_lock(&clk->lock);
 106
 107         if (++clk->enable == 1 && clk->ops->enable) {
 108                 ret = clk->ops->enable(clk);
 109                 if (ret < 0)
 110                         clk->enable--;
 111         }
 112
 113         mutex_unlock(&clk->lock);
 114
 115         return ret;
 116 }
 117 EXPORT_SYMBOL(v4l2_clk_enable);
 118
 119 /*
 120  * You might Oops if you try to disabled a disabled clock, because then the
 121  * driver isn't locked and could have been unloaded by now, so, don't do that
 122  */
 123 void v4l2_clk_disable(struct v4l2_clk *clk)
 124 {
 125         int enable;
 126
 127         mutex_lock(&clk->lock);
 128
 129         enable = --clk->enable;
 130         if (WARN(enable < 0, "Unbalanced %s() on %s:%s!\n", __func__,
 131                  clk->dev_id, clk->id))
 132                 clk->enable++;
 133         else if (!enable && clk->ops->disable)
 134                 clk->ops->disable(clk);
 135
 136         mutex_unlock(&clk->lock);
 137
 138         v4l2_clk_unlock_driver(clk);
 139 }
 140 EXPORT_SYMBOL(v4l2_clk_disable);
 141
 142 unsigned long v4l2_clk_get_rate(struct v4l2_clk *clk)
 143 {
 144         int ret = v4l2_clk_lock_driver(clk);
 145
 146         if (ret < 0)
 147                 return ret;
 148
 149         mutex_lock(&clk->lock);
 150         if (!clk->ops->get_rate)
 151                 ret = -ENOSYS;
 152         else
 153                 ret = clk->ops->get_rate(clk);
 154         mutex_unlock(&clk->lock);
 155
 156         v4l2_clk_unlock_driver(clk);
 157
 158         return ret;
 159 }
 160 EXPORT_SYMBOL(v4l2_clk_get_rate);
 161
 162 int v4l2_clk_set_rate(struct v4l2_clk *clk, unsigned long rate)
 163 {
 164         int ret = v4l2_clk_lock_driver(clk);
 165
 166         if (ret < 0)
 167                 return ret;
 168
 169         mutex_lock(&clk->lock);
 170         if (!clk->ops->set_rate)
 171                 ret = -ENOSYS;
 172         else
 173                 ret = clk->ops->set_rate(clk, rate);
 174         mutex_unlock(&clk->lock);
 175
 176         v4l2_clk_unlock_driver(clk);
 177
 178         return ret;
 179 }
 180 EXPORT_SYMBOL(v4l2_clk_set_rate);
 181
 182 struct v4l2_clk *v4l2_clk_register(const struct v4l2_clk_ops *ops,
 183                                    const char *dev_id,
 184                                    const char *id, void *priv)
 185 {
 186         struct v4l2_clk *clk;
 187         int ret;
 188
 189         if (!ops || !dev_id)
 190                 return ERR_PTR(-EINVAL);
 191
 192         clk = kzalloc(sizeof(struct v4l2_clk), GFP_KERNEL);
 193         if (!clk)
 194                 return ERR_PTR(-ENOMEM);
 195
 196         clk->id = kstrdup(id, GFP_KERNEL);
 197         clk->dev_id = kstrdup(dev_id, GFP_KERNEL);
 198         if ((id && !clk->id) || !clk->dev_id) {
 199                 ret = -ENOMEM;
 200                 goto ealloc;
 201         }
 202         clk->ops = ops;
 203         clk->priv = priv;
 204         atomic_set(&clk->use_count, 0);
 205         mutex_init(&clk->lock);
 206
 207         mutex_lock(&clk_lock);
 208         if (!IS_ERR(v4l2_clk_find(dev_id, id))) {
 209                 mutex_unlock(&clk_lock);
 210                 ret = -EEXIST;
 211                 goto eexist;
 212         }
 213         list_add_tail(&clk->list, &clk_list);
 214         mutex_unlock(&clk_lock);
 215
 216         return clk;
 217
 218 eexist:
 219 ealloc:
 220         kfree(clk->id);
 221         kfree(clk->dev_id);
 222         kfree(clk);
 223         return ERR_PTR(ret);
 224 }
 225 EXPORT_SYMBOL(v4l2_clk_register);
 226
 227 void v4l2_clk_unregister(struct v4l2_clk *clk)
 228 {
 229         if (WARN(atomic_read(&clk->use_count),
 230                  "%s(): Refusing to unregister ref-counted %s:%s clock!\n",
 231                  __func__, clk->dev_id, clk->id))
 232                 return;
 233
 234         mutex_lock(&clk_lock);
 235         list_del(&clk->list);
 236         mutex_unlock(&clk_lock);
 237
 238         kfree(clk->id);
 239         kfree(clk->dev_id);
 240         kfree(clk);
 241 }
 242 EXPORT_SYMBOL(v4l2_clk_unregister);