- add a simple implementation of a null device

git-svn-id: http://svn.lfbs.rwth-aachen.de/svn/scc/trunk/MetalSVM@117 315a16e6-25f9-4109-90ae-ca3045a26c18

fs/null.c

@@ -0,0 +1,106 @@
+/* 
+ * Copyright 2010 Stefan Lankes, Chair for Operating Systems,
+ *                               RWTH Aachen University
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * This file is part of MetalSVM. 
+ */
+
+#include <metalsvm/stdlib.h>
+#include <metalsvm/string.h>
+#include <metalsvm/stdio.h>
+#include <metalsvm/errno.h>
+#include <metalsvm/fs.h>
+
+/* Implementation of a simple null device */
+
+static ssize_t null_read(vfs_node_t* node, uint8_t* buffer, size_t size, off_t offset)
+{
+	memset(buffer, 0x00, size);
+
+	return size;
+}
+
+static ssize_t null_write(vfs_node_t* node, uint8_t* buffer, size_t size,  off_t offset)
+{
+	return size;
+}
+
+static int null_open(vfs_node_t* node)
+{
+	return 0;
+}
+
+static int null_close(vfs_node_t* node)
+{
+	return 0;
+}
+
+int null_init(vfs_node_t* node, const char* name)
+{
+	uint32_t i, j;
+	vfs_node_t* new_node;
+	dir_block_t* blockdir;
+	dirent_t* dirent;
+	block_list_t* blist;
+
+	if (BUILTIN_EXPECT(!node || !name, 0))
+		return -EINVAL;
+
+	if (BUILTIN_EXPECT(node->type != FS_DIRECTORY, 0))
+		return -EINVAL;
+
+	if (finddir_fs(node, name))
+		return -EINVAL;
+
+	new_node = kmalloc(sizeof(vfs_node_t));
+	if (BUILTIN_EXPECT(!new_node, 0))
+		return -ENOMEM;
+
+	memset(new_node, 0x00, sizeof(vfs_node_t));
+        new_node->type = FS_CHARDEVICE;
+        new_node->open = &null_open;
+        new_node->close = &null_close;
+        new_node->read = &null_read;
+	new_node->write = &null_write;
+        spinlock_init(&new_node->lock);
+
+	blist= &node->block_list;
+	do {
+		for(i=0; i<MAX_DATABLOCKS; i++) {
+			if (blist->data[i]) {
+				blockdir = (dir_block_t*) blist->data[i];
+				for(j=0; j<MAX_DIRENTRIES; j++) {
+					dirent = &blockdir->entries[j];
+					if (!dirent->vfs_node) {
+						dirent->vfs_node = new_node;
+						strncpy(dirent->name, name, MAX_FNAME);
+						return 0;
+					}
+				}
+			}
+		}
+
+		if (!blist->next) {
+			blist->next = (block_list_t*) kmalloc(sizeof(block_list_t));
+			if (blist->next)
+				memset(blist->next, 0x00, sizeof(block_list_t));
+		}
+
+	} while(blist);
+
+	kfree(new_node, sizeof(vfs_node_t));
+
+	return -ENOMEM;
+}