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	for (; idx >= 0; --idx)
84		kfree((*buf)->data[idx]);
85
86	kfree(*buf);
87	return -ENOMEM;
88}
89
90/**
91 * Copy the user data to the begin of the buffer and reset the processing
92 * iterator.
93 *
94 *   user_data: A pointer the data that is copied to the buffer.
95 *   size: The Number of bytes to copy.
96 */
97int drm_buffer_copy_from_user(struct drm_buffer *buf,
98			      void __user *user_data, int size)
99{
100	int nr_pages = size / PAGE_SIZE + 1;
101	int idx;
102
103	if (size > buf->size) {
104		DRM_ERROR("Requesting to copy %d bytes to a drm buffer with"
105				" %d bytes space\n",
106				size, buf->size);
107		return -EFAULT;
108	}
109
110	for (idx = 0; idx < nr_pages; ++idx) {
111
112		if (copy_from_user(buf->data[idx],
113			user_data + idx * PAGE_SIZE,
114			min(PAGE_SIZE, size - idx * PAGE_SIZE))) {
115			DRM_ERROR("Failed to copy user data (%p) to drm buffer"
116					" (%p) %dth page.\n",
117					user_data, buf, idx);
118			return -EFAULT;
119
120		}
121	}
122	buf->iterator = 0;
123	return 0;
124}
125
126/**
127 * Free the drm buffer object
128 */
129void drm_buffer_free(struct drm_buffer *buf)
130{
131
132	if (buf != NULL) {
133
134		int nr_pages = buf->size / PAGE_SIZE + 1;
135		int idx;
136		for (idx = 0; idx < nr_pages; ++idx)
137			kfree(buf->data[idx]);
138
139		kfree(buf);
140	}
141}
142
143/**
144 * Read an object from buffer that may be split to multiple parts. If object
145 * is not split function just returns the pointer to object in buffer. But in
146 * case of split object data is copied to given stack object that is suplied
147 * by caller.
148 *
149 * The processing location of the buffer is also advanced to the next byte
150 * after the object.
151 *
152 *   objsize: The size of the objet in bytes.
153 *   stack_obj: A pointer to a memory location where object can be copied.
154 */
155void *drm_buffer_read_object(struct drm_buffer *buf,
156		int objsize, void *stack_obj)
157{
158	int idx = drm_buffer_index(buf);
159	int page = drm_buffer_page(buf);
160	void *obj = NULL;
161
162	if (idx + objsize <= PAGE_SIZE) {
163		obj = &buf->data[page][idx];
164	} else {
165		/* The object is split which forces copy to temporary object.*/
166		int beginsz = PAGE_SIZE - idx;
167		memcpy(stack_obj, &buf->data[page][idx], beginsz);
168
169		memcpy(stack_obj + beginsz, &buf->data[page + 1][0],
170				objsize - beginsz);
171
172		obj = stack_obj;
173	}
174
175	drm_buffer_advance(buf, objsize);
176	return obj;
177}
178