patch-2.4.6 linux/Documentation/DocBook/procfs_example.c

• Lines: 250
• Date: Mon Jul 2 13:56:40 2001
• Orig file: v2.4.5/linux/Documentation/DocBook/procfs_example.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.5/linux/Documentation/DocBook/procfs_example.c linux/Documentation/DocBook/procfs_example.c
@@ -0,0 +1,249 @@
+/*
+ * 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/sched.h>
+#include <asm/uaccess.h>
+
+
+#define MODULE_VERSION "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, *tty_device, *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;
+
+	MOD_INC_USE_COUNT;
+	
+	len = sprintf(page, "jiffies = %ld\n",
+                      jiffies);
+
+	MOD_DEC_USE_COUNT;
+
+	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;
+
+	MOD_INC_USE_COUNT;
+	
+	len = sprintf(page, "%s = '%s'\n", 
+		      fb_data->name, fb_data->value);
+
+	MOD_DEC_USE_COUNT;
+
+	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;
+
+	MOD_INC_USE_COUNT;
+
+	if(count > FOOBAR_LEN)
+		len = FOOBAR_LEN;
+	else
+		len = count;
+
+	if(copy_from_user(fb_data->value, buffer, len)) {
+		MOD_DEC_USE_COUNT;
+		return -EFAULT;
+	}
+
+	fb_data->value[len] = '\0';
+
+	MOD_DEC_USE_COUNT;
+
+	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 tty device */
+	tty_device = proc_mknod("tty", S_IFCHR | 0666,
+				example_dir, MKDEV(5, 0));
+	if(tty_device == NULL) {
+		rv = -ENOMEM;
+		goto no_tty;
+	}
+	
+	tty_device->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_VERSION);
+	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_VERSION);
+}
+
+
+module_init(init_procfs_example);
+module_exit(cleanup_procfs_example);
+
+MODULE_AUTHOR("Erik Mouw");
+MODULE_DESCRIPTION("procfs examples");
+
+EXPORT_NO_SYMBOLS;