linux/include/drm/drm_buffer.h
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   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 <drm/drmP.h>
  39
  40struct 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 */
  50static 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 */
  57static 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 */
  64static 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 */
  72static 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 */
  83extern 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 */
  92extern 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 */
  98extern 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 */
 112extern 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 */
 127static 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 */
 141static 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
 149
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