Linux Device Drivers 3 examples

1 files changed, 109 insertions, 0 deletions

diff --git a/misc-modules/seq.c b/misc-modules/seq.c
new file mode 100644
index 0000000..59026a5
--- /dev/null
+++ b/misc-modules/seq.c
@@ -0,0 +1,109 @@
+/*
+ * Simple demonstration of the seq_file interface.
+ *
+ * $Id: seq.c,v 1.3 2004/09/26 07:02:43 gregkh Exp $
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/fs.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+
+MODULE_AUTHOR("Jonathan Corbet");
+MODULE_LICENSE("Dual BSD/GPL");
+
+
+
+/*
+ * The sequence iterator functions.  The position as seen by the
+ * filesystem is just the count that we return.
+ */
+static void *ct_seq_start(struct seq_file *s, loff_t *pos)
+{
+	loff_t *spos = kmalloc(sizeof(loff_t), GFP_KERNEL);
+	if (!spos)
+		return NULL;
+	*spos = *pos;
+	return spos;
+}
+
+static void *ct_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+	loff_t *spos = (loff_t *) v;
+	*pos = ++(*spos);
+	return spos;
+}
+
+static void ct_seq_stop(struct seq_file *s, void *v)
+{
+	kfree (v);
+}
+
+/*
+ * The show function.
+ */
+static int ct_seq_show(struct seq_file *s, void *v)
+{
+	loff_t *spos = (loff_t *) v;
+	seq_printf(s, "%Ld\n", *spos);
+	return 0;
+}
+
+/*
+ * Tie them all together into a set of seq_operations.
+ */
+static struct seq_operations ct_seq_ops = {
+	.start = ct_seq_start,
+	.next  = ct_seq_next,
+	.stop  = ct_seq_stop,
+	.show  = ct_seq_show
+};
+
+
+/*
+ * Time to set up the file operations for our /proc file.  In this case,
+ * all we need is an open function which sets up the sequence ops.
+ */
+
+static int ct_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &ct_seq_ops);
+};
+
+/*
+ * The file operations structure contains our open function along with
+ * set of the canned seq_ ops.
+ */
+static struct file_operations ct_file_ops = {
+	.owner   = THIS_MODULE,
+	.open    = ct_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = seq_release
+};
+	
+	
+/*
+ * Module setup and teardown.
+ */
+
+static int ct_init(void)
+{
+	struct proc_dir_entry *entry;
+
+	entry = create_proc_entry("sequence", 0, NULL);
+	if (entry)
+		entry->proc_fops = &ct_file_ops;
+	return 0;
+}
+
+static void ct_exit(void)
+{
+	remove_proc_entry("sequence", NULL);
+}
+
+module_init(ct_init);
+module_exit(ct_exit);