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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/DocBook/procfs_example.c
downloadlinux-stericsson-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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+/*
+ * procfs_example.c: an example proc interface
+ *
+ * Copyright (C) 2001, Erik Mouw (J.A.K.Mouw@its.tudelft.nl)
+ *
+ * This file accompanies the procfs-guide in the Linux kernel
+ * source. Its main use is to demonstrate the concepts and
+ * functions described in the guide.
+ *
+ * This software has been developed while working on the LART
+ * computing board (http://www.lart.tudelft.nl/), which is
+ * sponsored by the Mobile Multi-media Communications
+ * (http://www.mmc.tudelft.nl/) and Ubiquitous Communications
+ * (http://www.ubicom.tudelft.nl/) projects.
+ *
+ * The author can be reached at:
+ *
+ * Erik Mouw
+ * Information and Communication Theory Group
+ * Faculty of Information Technology and Systems
+ * Delft University of Technology
+ * P.O. Box 5031
+ * 2600 GA Delft
+ * The Netherlands
+ *
+ *
+ * This program is free software; you can redistribute
+ * it and/or modify it under the terms of the GNU General
+ * Public License as published by the Free Software
+ * Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be
+ * useful, but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place,
+ * Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/proc_fs.h>
+#include <linux/jiffies.h>
+#include <asm/uaccess.h>
+
+
+#define MODULE_VERS "1.0"
+#define MODULE_NAME "procfs_example"
+
+#define FOOBAR_LEN 8
+
+struct fb_data_t {
+ char name[FOOBAR_LEN + 1];
+ char value[FOOBAR_LEN + 1];
+};
+
+
+static struct proc_dir_entry *example_dir, *foo_file,
+ *bar_file, *jiffies_file, *symlink;
+
+
+struct fb_data_t foo_data, bar_data;
+
+
+static int proc_read_jiffies(char *page, char **start,
+ off_t off, int count,
+ int *eof, void *data)
+{
+ int len;
+
+ len = sprintf(page, "jiffies = %ld\n",
+ jiffies);
+
+ return len;
+}
+
+
+static int proc_read_foobar(char *page, char **start,
+ off_t off, int count,
+ int *eof, void *data)
+{
+ int len;
+ struct fb_data_t *fb_data = (struct fb_data_t *)data;
+
+ /* DON'T DO THAT - buffer overruns are bad */
+ len = sprintf(page, "%s = '%s'\n",
+ fb_data->name, fb_data->value);
+
+ return len;
+}
+
+
+static int proc_write_foobar(struct file *file,
+ const char *buffer,
+ unsigned long count,
+ void *data)
+{
+ int len;
+ struct fb_data_t *fb_data = (struct fb_data_t *)data;
+
+ if(count > FOOBAR_LEN)
+ len = FOOBAR_LEN;
+ else
+ len = count;
+
+ if(copy_from_user(fb_data->value, buffer, len))
+ return -EFAULT;
+
+ fb_data->value[len] = '\0';
+
+ return len;
+}
+
+
+static int __init init_procfs_example(void)
+{
+ int rv = 0;
+
+ /* create directory */
+ example_dir = proc_mkdir(MODULE_NAME, NULL);
+ if(example_dir == NULL) {
+ rv = -ENOMEM;
+ goto out;
+ }
+
+ example_dir->owner = THIS_MODULE;
+
+ /* create jiffies using convenience function */
+ jiffies_file = create_proc_read_entry("jiffies",
+ 0444, example_dir,
+ proc_read_jiffies,
+ NULL);
+ if(jiffies_file == NULL) {
+ rv = -ENOMEM;
+ goto no_jiffies;
+ }
+
+ jiffies_file->owner = THIS_MODULE;
+
+ /* create foo and bar files using same callback
+ * functions
+ */
+ foo_file = create_proc_entry("foo", 0644, example_dir);
+ if(foo_file == NULL) {
+ rv = -ENOMEM;
+ goto no_foo;
+ }
+
+ strcpy(foo_data.name, "foo");
+ strcpy(foo_data.value, "foo");
+ foo_file->data = &foo_data;
+ foo_file->read_proc = proc_read_foobar;
+ foo_file->write_proc = proc_write_foobar;
+ foo_file->owner = THIS_MODULE;
+
+ bar_file = create_proc_entry("bar", 0644, example_dir);
+ if(bar_file == NULL) {
+ rv = -ENOMEM;
+ goto no_bar;
+ }
+
+ strcpy(bar_data.name, "bar");
+ strcpy(bar_data.value, "bar");
+ bar_file->data = &bar_data;
+ bar_file->read_proc = proc_read_foobar;
+ bar_file->write_proc = proc_write_foobar;
+ bar_file->owner = THIS_MODULE;
+
+ /* create symlink */
+ symlink = proc_symlink("jiffies_too", example_dir,
+ "jiffies");
+ if(symlink == NULL) {
+ rv = -ENOMEM;
+ goto no_symlink;
+ }
+
+ symlink->owner = THIS_MODULE;
+
+ /* everything OK */
+ printk(KERN_INFO "%s %s initialised\n",
+ MODULE_NAME, MODULE_VERS);
+ return 0;
+
+no_symlink:
+ remove_proc_entry("tty", example_dir);
+no_tty:
+ remove_proc_entry("bar", example_dir);
+no_bar:
+ remove_proc_entry("foo", example_dir);
+no_foo:
+ remove_proc_entry("jiffies", example_dir);
+no_jiffies:
+ remove_proc_entry(MODULE_NAME, NULL);
+out:
+ return rv;
+}
+
+
+static void __exit cleanup_procfs_example(void)
+{
+ remove_proc_entry("jiffies_too", example_dir);
+ remove_proc_entry("tty", example_dir);
+ remove_proc_entry("bar", example_dir);
+ remove_proc_entry("foo", example_dir);
+ remove_proc_entry("jiffies", example_dir);
+ remove_proc_entry(MODULE_NAME, NULL);
+
+ printk(KERN_INFO "%s %s removed\n",
+ MODULE_NAME, MODULE_VERS);
+}
+
+
+module_init(init_procfs_example);
+module_exit(cleanup_procfs_example);
+
+MODULE_AUTHOR("Erik Mouw");
+MODULE_DESCRIPTION("procfs examples");