Root/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_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 */
44int 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
81error_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}
93EXPORT_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 */
102int 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 (DRM_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}
130EXPORT_SYMBOL(drm_buffer_copy_from_user);
131
132/**
133 * Free the drm buffer object
134 */
135void 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}
148EXPORT_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 */
162void *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}
185EXPORT_SYMBOL(drm_buffer_read_object);
186

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