PPP Porting

3.2.3Entry points and support calls

When you have compiled the PPP code, you must add the hooks to connect PPP to your system and link your line functions to the PPP code. This is generally done in ppp_port_init() in the file ppp_port.c. PPP entry points on page 5-18 provides detailed information about all PPP calls you should be aware of.

There are three classes of functions you must implement:

•Support functions PPP needs from the host system, for example, time tick, reading NV parameters, and memory allocation. These include:

—prep_ppp(), which initializes the PPP code for use

—ppp_timeisup(), the clock tick function

—the _ALLOC() functions.

•Line drivers, functions for sending and receiving bytes, and connection management. These are detailed in Serial line drivers on page 5-10.

•IP Support, functions for sending and receiving IP packets (see Network interfaces on page 4-15). This is implemented by way of the NET structure in the ARM IP stack, so that the IP layer does not treat PPP any differently than it would any other media, such as Ethernet or SLIP.

You should review the list of function calls in PPP entry points on page 5-18. At a minimum you need to ensure that:

•prep_ppp() and ppp_timeisup() are called as appropriate

•the allocation functions are properly mapped

•a line driver is available.

For most ports, the line driver is the majority of the work.

To bind PPP to the ARM TCP/IP stack, you must call prep_ppp() from prep_ifaces() in your ipport.c file. See prep_ifaces() on page 4-12.