v4.19.13 snapshot.
diff --git a/include/linux/hdlc.h b/include/linux/hdlc.h
new file mode 100644
index 0000000..97585d9
--- /dev/null
+++ b/include/linux/hdlc.h
@@ -0,0 +1,118 @@
+/*
+ * Generic HDLC support routines for Linux
+ *
+ * Copyright (C) 1999-2005 Krzysztof Halasa <khc@pm.waw.pl>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ */
+#ifndef __HDLC_H
+#define __HDLC_H
+
+
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/hdlc/ioctl.h>
+#include <uapi/linux/hdlc.h>
+
+/* This structure is a private property of HDLC protocols.
+ Hardware drivers have no interest here */
+
+struct hdlc_proto {
+ int (*open)(struct net_device *dev);
+ void (*close)(struct net_device *dev);
+ void (*start)(struct net_device *dev); /* if open & DCD */
+ void (*stop)(struct net_device *dev); /* if open & !DCD */
+ void (*detach)(struct net_device *dev);
+ int (*ioctl)(struct net_device *dev, struct ifreq *ifr);
+ __be16 (*type_trans)(struct sk_buff *skb, struct net_device *dev);
+ int (*netif_rx)(struct sk_buff *skb);
+ netdev_tx_t (*xmit)(struct sk_buff *skb, struct net_device *dev);
+ struct module *module;
+ struct hdlc_proto *next; /* next protocol in the list */
+};
+
+
+/* Pointed to by netdev_priv(dev) */
+typedef struct hdlc_device {
+ /* used by HDLC layer to take control over HDLC device from hw driver*/
+ int (*attach)(struct net_device *dev,
+ unsigned short encoding, unsigned short parity);
+
+ /* hardware driver must handle this instead of dev->hard_start_xmit */
+ netdev_tx_t (*xmit)(struct sk_buff *skb, struct net_device *dev);
+
+ /* Things below are for HDLC layer internal use only */
+ const struct hdlc_proto *proto;
+ int carrier;
+ int open;
+ spinlock_t state_lock;
+ void *state;
+ void *priv;
+} hdlc_device;
+
+
+
+/* Exported from hdlc module */
+
+/* Called by hardware driver when a user requests HDLC service */
+int hdlc_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd);
+
+/* Must be used by hardware driver on module startup/exit */
+#define register_hdlc_device(dev) register_netdev(dev)
+void unregister_hdlc_device(struct net_device *dev);
+
+
+void register_hdlc_protocol(struct hdlc_proto *proto);
+void unregister_hdlc_protocol(struct hdlc_proto *proto);
+
+struct net_device *alloc_hdlcdev(void *priv);
+
+static inline struct hdlc_device* dev_to_hdlc(struct net_device *dev)
+{
+ return netdev_priv(dev);
+}
+
+static __inline__ void debug_frame(const struct sk_buff *skb)
+{
+ int i;
+
+ for (i=0; i < skb->len; i++) {
+ if (i == 100) {
+ printk("...\n");
+ return;
+ }
+ printk(" %02X", skb->data[i]);
+ }
+ printk("\n");
+}
+
+
+/* Must be called by hardware driver when HDLC device is being opened */
+int hdlc_open(struct net_device *dev);
+/* Must be called by hardware driver when HDLC device is being closed */
+void hdlc_close(struct net_device *dev);
+/* Must be pointed to by hw driver's dev->netdev_ops->ndo_start_xmit */
+netdev_tx_t hdlc_start_xmit(struct sk_buff *skb, struct net_device *dev);
+
+int attach_hdlc_protocol(struct net_device *dev, struct hdlc_proto *proto,
+ size_t size);
+/* May be used by hardware driver to gain control over HDLC device */
+int detach_hdlc_protocol(struct net_device *dev);
+
+static __inline__ __be16 hdlc_type_trans(struct sk_buff *skb,
+ struct net_device *dev)
+{
+ hdlc_device *hdlc = dev_to_hdlc(dev);
+
+ skb->dev = dev;
+ skb_reset_mac_header(skb);
+
+ if (hdlc->proto->type_trans)
+ return hdlc->proto->type_trans(skb, dev);
+ else
+ return htons(ETH_P_HDLC);
+}
+
+#endif /* __HDLC_H */