linux/linux-5.18.11/Documentation/networking/6lowpan.rst

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.. SPDX-License-Identifier: GPL-2.0
==============================================
Netdev private dataroom for 6lowpan interfaces
==============================================
All 6lowpan able net devices, means all interfaces with ARPHRD_6LOWPAN,
must have "struct lowpan_priv" placed at beginning of netdev_priv.
The priv_size of each interface should be calculate by::
dev->priv_size = LOWPAN_PRIV_SIZE(LL_6LOWPAN_PRIV_DATA);
Where LL_PRIV_6LOWPAN_DATA is sizeof linklayer 6lowpan private data struct.
To access the LL_PRIV_6LOWPAN_DATA structure you can cast::
lowpan_priv(dev)-priv;
to your LL_6LOWPAN_PRIV_DATA structure.
Before registering the lowpan netdev interface you must run::
lowpan_netdev_setup(dev, LOWPAN_LLTYPE_FOOBAR);
wheres LOWPAN_LLTYPE_FOOBAR is a define for your 6LoWPAN linklayer type of
enum lowpan_lltypes.
Example to evaluate the private usually you can do::
static inline struct lowpan_priv_foobar *
lowpan_foobar_priv(struct net_device *dev)
{
return (struct lowpan_priv_foobar *)lowpan_priv(dev)->priv;
}
switch (dev->type) {
case ARPHRD_6LOWPAN:
lowpan_priv = lowpan_priv(dev);
/* do great stuff which is ARPHRD_6LOWPAN related */
switch (lowpan_priv->lltype) {
case LOWPAN_LLTYPE_FOOBAR:
/* do 802.15.4 6LoWPAN handling here */
lowpan_foobar_priv(dev)->bar = foo;
break;
...
}
break;
...
}
In case of generic 6lowpan branch ("net/6lowpan") you can remove the check
on ARPHRD_6LOWPAN, because you can be sure that these function are called
by ARPHRD_6LOWPAN interfaces.