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);