include/drm/drm_buffer.h

   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 #ifndef _DRM_BUFFER_H_
  36 #define _DRM_BUFFER_H_
  37
  38 #include "drmP.h"
  39
  40 struct drm_buffer {
  41         int iterator;
  42         int size;
  43         char *data[];
  44 };
  45
  46
  47 /**
  48  * Return the index of page that buffer is currently pointing at.
  49  */
  50 static inline int drm_buffer_page(struct drm_buffer *buf)
  51 {
  52         return buf->iterator / PAGE_SIZE;
  53 }
  54 /**
  55  * Return the index of the current byte in the page
  56  */
  57 static inline int drm_buffer_index(struct drm_buffer *buf)
  58 {
  59         return buf->iterator & (PAGE_SIZE - 1);
  60 }
  61 /**
  62  * Return number of bytes that is left to process
  63  */
  64 static inline int drm_buffer_unprocessed(struct drm_buffer *buf)
  65 {
  66         return buf->size - buf->iterator;
  67 }
  68
  69 /**
  70  * Advance the buffer iterator number of bytes that is given.
  71  */
  72 static inline void drm_buffer_advance(struct drm_buffer *buf, int bytes)
  73 {
  74         buf->iterator += bytes;
  75 }
  76
  77 /**
  78  * Allocate the drm buffer object.
  79  *
  80  *   buf: A pointer to a pointer where the object is stored.
  81  *   size: The number of bytes to allocate.
  82  */
  83 extern int drm_buffer_alloc(struct drm_buffer **buf, int size);
  84
  85 /**
  86  * Copy the user data to the begin of the buffer and reset the processing
  87  * iterator.
  88  *
  89  *   user_data: A pointer the data that is copied to the buffer.
  90  *   size: The Number of bytes to copy.
  91  */
  92 extern int drm_buffer_copy_from_user(struct drm_buffer *buf,
  93                 void __user *user_data, int size);
  94
  95 /**
  96  * Free the drm buffer object
  97  */
  98 extern void drm_buffer_free(struct drm_buffer *buf);
  99
 100 /**
 101  * Read an object from buffer that may be split to multiple parts. If object
 102  * is not split function just returns the pointer to object in buffer. But in
 103  * case of split object data is copied to given stack object that is suplied
 104  * by caller.
 105  *
 106  * The processing location of the buffer is also advanced to the next byte
 107  * after the object.
 108  *
 109  *   objsize: The size of the objet in bytes.
 110  *   stack_obj: A pointer to a memory location where object can be copied.
 111  */
 112 extern void *drm_buffer_read_object(struct drm_buffer *buf,
 113                 int objsize, void *stack_obj);
 114
 115 /**
 116  * Returns the pointer to the dword which is offset number of elements from the
 117  * current processing location.
 118  *
 119  * Caller must make sure that dword is not split in the buffer. This
 120  * requirement is easily met if all the sizes of objects in buffer are
 121  * multiples of dword and PAGE_SIZE is multiple dword.
 122  *
 123  * Call to this function doesn't change the processing location.
 124  *
 125  *   offset: The index of the dword relative to the internat iterator.
 126  */
 127 static inline void *drm_buffer_pointer_to_dword(struct drm_buffer *buffer,
 128                 int offset)
 129 {
 130         int iter = buffer->iterator + offset * 4;
 131         return &buffer->data[iter / PAGE_SIZE][iter & (PAGE_SIZE - 1)];
 132 }
 133 /**
 134  * Returns the pointer to the dword which is offset number of elements from
 135  * the current processing location.
 136  *
 137  * Call to this function doesn't change the processing location.
 138  *
 139  *   offset: The index of the byte relative to the internat iterator.
 140  */
 141 static inline void *drm_buffer_pointer_to_byte(struct drm_buffer *buffer,
 142                 int offset)
 143 {
 144         int iter = buffer->iterator + offset;
 145         return &buffer->data[iter / PAGE_SIZE][iter & (PAGE_SIZE - 1)];
 146 }
 147
 148 #endif