drivers/gpu/drm/drm_buffer.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2010 Pauli Nieminen.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  21  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  22  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  23  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  24  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  *
  27  **************************************************************************/
  28 /*
  29  * Multipart buffer for coping data which is larger than the page size.
  30  *
  31  * Authors:
  32  * Pauli Nieminen <suokkos-at-gmail-dot-com>
  33  */
  34
  35 #include <linux/export.h>
  36 #include <drm/drm_buffer.h>
  37
  38 /**
  39  * Allocate the drm buffer object.
  40  *
  41  *   buf: Pointer to a pointer where the object is stored.
  42  *   size: The number of bytes to allocate.
  43  */
  44 int drm_buffer_alloc(struct drm_buffer **buf, int size)
  45 {
  46         int nr_pages = size / PAGE_SIZE + 1;
  47         int idx;
  48
  49         /* Allocating pointer table to end of structure makes drm_buffer
  50          * variable sized */
  51         *buf = kzalloc(sizeof(struct drm_buffer) + nr_pages*sizeof(char *),
  52                         GFP_KERNEL);
  53
  54         if (*buf == NULL) {
  55                 DRM_ERROR("Failed to allocate drm buffer object to hold"
  56                                 " %d bytes in %d pages.\n",
  57                                 size, nr_pages);
  58                 return -ENOMEM;
  59         }
  60
  61         (*buf)->size = size;
  62
  63         for (idx = 0; idx < nr_pages; ++idx) {
  64
  65                 (*buf)->data[idx] =
  66                         kmalloc(min(PAGE_SIZE, size - idx * PAGE_SIZE),
  67                                 GFP_KERNEL);
  68
  69
  70                 if ((*buf)->data[idx] == NULL) {
  71                         DRM_ERROR("Failed to allocate %dth page for drm"
  72                                         " buffer with %d bytes and %d pages.\n",
  73                                         idx + 1, size, nr_pages);
  74                         goto error_out;
  75                 }
  76
  77         }
  78
  79         return 0;
  80
  81 error_out:
  82
  83         /* Only last element can be null pointer so check for it first. */
  84         if ((*buf)->data[idx])
  85                 kfree((*buf)->data[idx]);
  86
  87         for (--idx; idx >= 0; --idx)
  88                 kfree((*buf)->data[idx]);
  89
  90         kfree(*buf);
  91         return -ENOMEM;
  92 }
  93 EXPORT_SYMBOL(drm_buffer_alloc);
  94
  95 /**
  96  * Copy the user data to the begin of the buffer and reset the processing
  97  * iterator.
  98  *
  99  *   user_data: A pointer the data that is copied to the buffer.
 100  *   size: The Number of bytes to copy.
 101  */
 102 int drm_buffer_copy_from_user(struct drm_buffer *buf,
 103                               void __user *user_data, int size)
 104 {
 105         int nr_pages = size / PAGE_SIZE + 1;
 106         int idx;
 107
 108         if (size > buf->size) {
 109                 DRM_ERROR("Requesting to copy %d bytes to a drm buffer with"
 110                                 " %d bytes space\n",
 111                                 size, buf->size);
 112                 return -EFAULT;
 113         }
 114
 115         for (idx = 0; idx < nr_pages; ++idx) {
 116
 117                 if (copy_from_user(buf->data[idx],
 118                         user_data + idx * PAGE_SIZE,
 119                         min(PAGE_SIZE, size - idx * PAGE_SIZE))) {
 120                         DRM_ERROR("Failed to copy user data (%p) to drm buffer"
 121                                         " (%p) %dth page.\n",
 122                                         user_data, buf, idx);
 123                         return -EFAULT;
 124
 125                 }
 126         }
 127         buf->iterator = 0;
 128         return 0;
 129 }
 130 EXPORT_SYMBOL(drm_buffer_copy_from_user);
 131
 132 /**
 133  * Free the drm buffer object
 134  */
 135 void drm_buffer_free(struct drm_buffer *buf)
 136 {
 137
 138         if (buf != NULL) {
 139
 140                 int nr_pages = buf->size / PAGE_SIZE + 1;
 141                 int idx;
 142                 for (idx = 0; idx < nr_pages; ++idx)
 143                         kfree(buf->data[idx]);
 144
 145                 kfree(buf);
 146         }
 147 }
 148 EXPORT_SYMBOL(drm_buffer_free);
 149
 150 /**
 151  * Read an object from buffer that may be split to multiple parts. If object
 152  * is not split function just returns the pointer to object in buffer. But in
 153  * case of split object data is copied to given stack object that is suplied
 154  * by caller.
 155  *
 156  * The processing location of the buffer is also advanced to the next byte
 157  * after the object.
 158  *
 159  *   objsize: The size of the objet in bytes.
 160  *   stack_obj: A pointer to a memory location where object can be copied.
 161  */
 162 void *drm_buffer_read_object(struct drm_buffer *buf,
 163                 int objsize, void *stack_obj)
 164 {
 165         int idx = drm_buffer_index(buf);
 166         int page = drm_buffer_page(buf);
 167         void *obj = NULL;
 168
 169         if (idx + objsize <= PAGE_SIZE) {
 170                 obj = &buf->data[page][idx];
 171         } else {
 172                 /* The object is split which forces copy to temporary object.*/
 173                 int beginsz = PAGE_SIZE - idx;
 174                 memcpy(stack_obj, &buf->data[page][idx], beginsz);
 175
 176                 memcpy(stack_obj + beginsz, &buf->data[page + 1][0],
 177                                 objsize - beginsz);
 178
 179                 obj = stack_obj;
 180         }
 181
 182         drm_buffer_advance(buf, objsize);
 183         return obj;
 184 }
 185 EXPORT_SYMBOL(drm_buffer_read_object);