1 /* -*- mode: c; c-basic-offset: 8; -*-
2 * vim: noexpandtab sw=8 ts=8 sts=0:
4 * file.c - operations for regular (text) files.
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * General Public License for more details.
16 * You should have received a copy of the GNU General Public
17 * License along with this program; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 021110-1307, USA.
22 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
24 * configfs Copyright (C) 2005 Oracle. All rights reserved.
28 #include <linux/module.h>
29 #include <linux/dnotify.h>
30 #include <linux/slab.h>
31 #include <asm/uaccess.h>
32 #include <asm/semaphore.h>
34 #include <linux/configfs.h>
35 #include "configfs_internal.h"
38 struct configfs_buffer {
42 struct configfs_item_operations * ops;
49 * fill_read_buffer - allocate and fill buffer from item.
50 * @dentry: dentry pointer.
51 * @buffer: data buffer for file.
53 * Allocate @buffer->page, if it hasn't been already, then call the
54 * config_item's show() method to fill the buffer with this attribute's
56 * This is called only once, on the file's first read.
58 static int fill_read_buffer(struct dentry * dentry, struct configfs_buffer * buffer)
60 struct configfs_attribute * attr = to_attr(dentry);
61 struct config_item * item = to_item(dentry->d_parent);
62 struct configfs_item_operations * ops = buffer->ops;
67 buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
71 count = ops->show_attribute(item,attr,buffer->page);
72 buffer->needs_read_fill = 0;
73 BUG_ON(count > (ssize_t)PAGE_SIZE);
75 buffer->count = count;
83 * flush_read_buffer - push buffer to userspace.
84 * @buffer: data buffer for file.
85 * @userbuf: user-passed buffer.
86 * @count: number of bytes requested.
87 * @ppos: file position.
89 * Copy the buffer we filled in fill_read_buffer() to userspace.
90 * This is done at the reader's leisure, copying and advancing
91 * the amount they specify each time.
92 * This may be called continuously until the buffer is empty.
94 static int flush_read_buffer(struct configfs_buffer * buffer, char __user * buf,
95 size_t count, loff_t * ppos)
99 if (*ppos > buffer->count)
102 if (count > (buffer->count - *ppos))
103 count = buffer->count - *ppos;
105 error = copy_to_user(buf,buffer->page + *ppos,count);
108 return error ? -EFAULT : count;
112 * configfs_read_file - read an attribute.
113 * @file: file pointer.
114 * @buf: buffer to fill.
115 * @count: number of bytes to read.
116 * @ppos: starting offset in file.
118 * Userspace wants to read an attribute file. The attribute descriptor
119 * is in the file's ->d_fsdata. The target item is in the directory's
122 * We call fill_read_buffer() to allocate and fill the buffer from the
123 * item's show() method exactly once (if the read is happening from
124 * the beginning of the file). That should fill the entire buffer with
125 * all the data the item has to offer for that attribute.
126 * We then call flush_read_buffer() to copy the buffer to userspace
127 * in the increments specified.
131 configfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos)
133 struct configfs_buffer * buffer = file->private_data;
137 if (buffer->needs_read_fill) {
138 if ((retval = fill_read_buffer(file->f_dentry,buffer)))
141 pr_debug("%s: count = %d, ppos = %lld, buf = %s\n",
142 __FUNCTION__,count,*ppos,buffer->page);
143 retval = flush_read_buffer(buffer,buf,count,ppos);
151 * fill_write_buffer - copy buffer from userspace.
152 * @buffer: data buffer for file.
153 * @userbuf: data from user.
154 * @count: number of bytes in @userbuf.
156 * Allocate @buffer->page if it hasn't been already, then
157 * copy the user-supplied buffer into it.
161 fill_write_buffer(struct configfs_buffer * buffer, const char __user * buf, size_t count)
166 buffer->page = (char *)get_zeroed_page(GFP_KERNEL);
170 if (count > PAGE_SIZE)
172 error = copy_from_user(buffer->page,buf,count);
173 buffer->needs_read_fill = 1;
174 return error ? -EFAULT : count;
179 * flush_write_buffer - push buffer to config_item.
180 * @file: file pointer.
181 * @buffer: data buffer for file.
183 * Get the correct pointers for the config_item and the attribute we're
184 * dealing with, then call the store() method for the attribute,
185 * passing the buffer that we acquired in fill_write_buffer().
189 flush_write_buffer(struct dentry * dentry, struct configfs_buffer * buffer, size_t count)
191 struct configfs_attribute * attr = to_attr(dentry);
192 struct config_item * item = to_item(dentry->d_parent);
193 struct configfs_item_operations * ops = buffer->ops;
195 return ops->store_attribute(item,attr,buffer->page,count);
200 * configfs_write_file - write an attribute.
201 * @file: file pointer
202 * @buf: data to write
203 * @count: number of bytes
204 * @ppos: starting offset
206 * Similar to configfs_read_file(), though working in the opposite direction.
207 * We allocate and fill the data from the user in fill_write_buffer(),
208 * then push it to the config_item in flush_write_buffer().
209 * There is no easy way for us to know if userspace is only doing a partial
210 * write, so we don't support them. We expect the entire buffer to come
211 * on the first write.
212 * Hint: if you're writing a value, first read the file, modify only the
213 * the value you're changing, then write entire buffer back.
217 configfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
219 struct configfs_buffer * buffer = file->private_data;
222 count = fill_write_buffer(buffer,buf,count);
224 count = flush_write_buffer(file->f_dentry,buffer,count);
231 static int check_perm(struct inode * inode, struct file * file)
233 struct config_item *item = configfs_get_config_item(file->f_dentry->d_parent);
234 struct configfs_attribute * attr = to_attr(file->f_dentry);
235 struct configfs_buffer * buffer;
236 struct configfs_item_operations * ops = NULL;
242 /* Grab the module reference for this attribute if we have one */
243 if (!try_module_get(attr->ca_owner)) {
249 ops = item->ci_type->ct_item_ops;
253 /* File needs write support.
254 * The inode's perms must say it's ok,
255 * and we must have a store method.
257 if (file->f_mode & FMODE_WRITE) {
259 if (!(inode->i_mode & S_IWUGO) || !ops->store_attribute)
264 /* File needs read support.
265 * The inode's perms must say it's ok, and we there
266 * must be a show method for it.
268 if (file->f_mode & FMODE_READ) {
269 if (!(inode->i_mode & S_IRUGO) || !ops->show_attribute)
273 /* No error? Great, allocate a buffer for the file, and store it
274 * it in file->private_data for easy access.
276 buffer = kmalloc(sizeof(struct configfs_buffer),GFP_KERNEL);
278 memset(buffer,0,sizeof(struct configfs_buffer));
279 init_MUTEX(&buffer->sem);
280 buffer->needs_read_fill = 1;
282 file->private_data = buffer;
292 module_put(attr->ca_owner);
295 config_item_put(item);
299 static int configfs_open_file(struct inode * inode, struct file * filp)
301 return check_perm(inode,filp);
304 static int configfs_release(struct inode * inode, struct file * filp)
306 struct config_item * item = to_item(filp->f_dentry->d_parent);
307 struct configfs_attribute * attr = to_attr(filp->f_dentry);
308 struct module * owner = attr->ca_owner;
309 struct configfs_buffer * buffer = filp->private_data;
312 config_item_put(item);
313 /* After this point, attr should not be accessed. */
318 free_page((unsigned long)buffer->page);
324 struct file_operations configfs_file_operations = {
325 .read = configfs_read_file,
326 .write = configfs_write_file,
327 .llseek = generic_file_llseek,
328 .open = configfs_open_file,
329 .release = configfs_release,
333 int configfs_add_file(struct dentry * dir, const struct configfs_attribute * attr, int type)
335 struct configfs_dirent * parent_sd = dir->d_fsdata;
336 umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
339 down(&dir->d_inode->i_sem);
340 error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode, type);
341 up(&dir->d_inode->i_sem);
348 * configfs_create_file - create an attribute file for an item.
349 * @item: item we're creating for.
350 * @attr: atrribute descriptor.
353 int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
355 BUG_ON(!item || !item->ci_dentry || !attr);
357 return configfs_add_file(item->ci_dentry, attr,