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* Generic HDLC support routines for Linux
* Copyright (C) 1999-2005 Krzysztof Halasa <>
* 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(" %02X", skb->data[i]);
/* 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;
if (hdlc->proto->type_trans)
return hdlc->proto->type_trans(skb, dev);
return htons(ETH_P_HDLC);
#endif /* __HDLC_H */