atm: separate ATM_GETNAMES handling from the rest of atm_dev_ioctl()

atm_dev_ioctl() does copyin in two different ways - one for
ATM_GETNAMES, another for everything else.  Start with separating
the former into a new helper (atm_getnames()).  The next step
will be to lift the copyin into the callers.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

net/atm/ioctl.c

@@ -162,7 +162,11 @@ static int do_vcc_ioctl(struct socket *sock, unsigned int cmd,
 	if (error != -ENOIOCTLCMD)
 		goto done;
 
+	if (cmd == ATM_GETNAMES) {
+		error = atm_getnames(argp, compat);
+	} else {
 		error = atm_dev_ioctl(cmd, argp, compat);
+	}
 
 done:
 	return error;

net/atm/resources.c

@@ -193,18 +193,15 @@ static int fetch_stats(struct atm_dev *dev, struct atm_dev_stats __user *arg,
 	return error ? -EFAULT : 0;
 }
 
-int atm_dev_ioctl(unsigned int cmd, void __user *arg, int compat)
+int atm_getnames(void __user *arg, int compat)
 {
 	void __user *buf;
-	int error, len, number, size = 0;
+	int error, len, size = 0;
 	struct atm_dev *dev;
 	struct list_head *p;
 	int *tmp_buf, *tmp_p;
-	int __user *sioc_len;
 	int __user *iobuf_len;
 
-	switch (cmd) {
-	case ATM_GETNAMES:
 	if (IS_ENABLED(CONFIG_COMPAT) && compat) {
 #ifdef CONFIG_COMPAT
 		struct compat_atm_iobuf __user *ciobuf = arg;
@@ -245,9 +242,14 @@ int atm_dev_ioctl(unsigned int cmd, void __user *arg, int compat)
 		? -EFAULT : 0;
 	kfree(tmp_buf);
 	return error;
-	default:
-		break;
-	}
+}
+
+int atm_dev_ioctl(unsigned int cmd, void __user *arg, int compat)
+{
+	void __user *buf;
+	int error, len, number, size = 0;
+	struct atm_dev *dev;
+	int __user *sioc_len;
 
 	if (IS_ENABLED(CONFIG_COMPAT) && compat) {
 #ifdef CONFIG_COMPAT

net/atm/resources.h

@@ -14,6 +14,7 @@
 extern struct list_head atm_devs;
 extern struct mutex atm_dev_mutex;
 
+int atm_getnames(void __user *arg, int compat);
 int atm_dev_ioctl(unsigned int cmd, void __user *arg, int compat);