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  */
drm_buffer_alloc(struct drm_buffer ** buf,int size)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  */
drm_buffer_copy_from_user(struct drm_buffer * buf,void __user * user_data,int size)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 (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 }
130 EXPORT_SYMBOL(drm_buffer_copy_from_user);
131 
132 /**
133  * Free the drm buffer object
134  */
drm_buffer_free(struct drm_buffer * buf)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  */
drm_buffer_read_object(struct drm_buffer * buf,int objsize,void * stack_obj)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);
186