ADD file via upload

fs/char_dev.c

@@ -0,0 +1,104 @@
+/*
+ *  linux/fs/char_dev.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+#include <errno.h>
+#include <sys/types.h>
+
+#include <linux/sched.h>
+#include <linux/kernel.h>
+
+#include <asm/segment.h>
+#include <asm/io.h>
+
+extern int tty_read(unsigned minor,char * buf,int count);
+extern int tty_write(unsigned minor,char * buf,int count);
+
+typedef (*crw_ptr)(int rw,unsigned minor,char * buf,int count,off_t * pos);
+
+static int rw_ttyx(int rw,unsigned minor,char * buf,int count,off_t * pos)
+{
+	return ((rw==READ)?tty_read(minor,buf,count):
+		tty_write(minor,buf,count));
+}
+
+static int rw_tty(int rw,unsigned minor,char * buf,int count, off_t * pos)
+{
+	if (current->tty<0)
+		return -EPERM;
+	return rw_ttyx(rw,current->tty,buf,count,pos);
+}
+
+static int rw_ram(int rw,char * buf, int count, off_t *pos)
+{
+	return -EIO;
+}
+
+static int rw_mem(int rw,char * buf, int count, off_t * pos)
+{
+	return -EIO;
+}
+
+static int rw_kmem(int rw,char * buf, int count, off_t * pos)
+{
+	return -EIO;
+}
+
+static int rw_port(int rw,char * buf, int count, off_t * pos)
+{
+	int i=*pos;
+
+	while (count-->0 && i<65536) {
+		if (rw==READ)
+			put_fs_byte(inb(i),buf++);
+		else
+			outb(get_fs_byte(buf++),i);
+		i++;
+	}
+	i -= *pos;
+	*pos += i;
+	return i;
+}
+
+static int rw_memory(int rw, unsigned minor, char * buf, int count, off_t * pos)
+{
+	switch(minor) {
+		case 0:
+			return rw_ram(rw,buf,count,pos);
+		case 1:
+			return rw_mem(rw,buf,count,pos);
+		case 2:
+			return rw_kmem(rw,buf,count,pos);
+		case 3:
+			return (rw==READ)?0:count;	/* rw_null */
+		case 4:
+			return rw_port(rw,buf,count,pos);
+		default:
+			return -EIO;
+	}
+}
+
+#define NRDEVS ((sizeof (crw_table))/(sizeof (crw_ptr)))
+
+static crw_ptr crw_table[]={
+	NULL,		/* nodev */
+	rw_memory,	/* /dev/mem etc */
+	NULL,		/* /dev/fd */
+	NULL,		/* /dev/hd */
+	rw_ttyx,	/* /dev/ttyx */
+	rw_tty,		/* /dev/tty */
+	NULL,		/* /dev/lp */
+	NULL};		/* unnamed pipes */
+
+int rw_char(int rw,int dev, char * buf, int count, off_t * pos)
+{
+	crw_ptr call_addr;
+
+	if (MAJOR(dev)>=NRDEVS)
+		return -ENODEV;
+	if (!(call_addr=crw_table[MAJOR(dev)]))
+		return -ENODEV;
+	return call_addr(rw,MINOR(dev),buf,count,pos);
+}