1pktdrive(3z) z88dk Programmer's Manual pktdrive(3z)
2
6 pktdrive - packet driver descriptor structure
7
9 #include <net/device.h>
10
12 The pktdrive structure defines access to a device, it is only used by
13 the ZSock kernel. Should you wish to write a packet driver then this
14 structure should be filled with the relevent routines.
15 All external packet drivers run at address 8192 ($2000) and it as this
17 address that the structure should be placed. Had z88dk the capability
18 pktdrive would be defined as follows:
19 struct pktdrive {
21 char magic[10];
22 char *type;
23 char *copymsg;
24 void (*initfunc)(void);
25 void (*queuefn)(void *pkt, size_t len);
26 void *(*packetfn)(void);
27 void *(*sendfn)(void);
28 int (*readfn)(void);
29 void (*onlinefn)();
30 void (*offlinefn)(int);
31 int (*statusfn)(void);
32 };
33 The members of the pktdrive structure are:
35 magic Magic to identifier the file as a packet driver, this is defined
37 as ZS0PKTDRV
38 type A pointer to the type of the device
40 copymsg
42 A pointer to the copyright message
43 initfunc
45 A function that initialises the device during the initial con‐
46 figurationin this function.
47 queuefn
49 A function that stores outgoing backets in a queue pending send‐
50 ing. Depending on the speed of the device it may also inject
51 packets into the interface.
52 packetfn
54 A function that returns the address of the incoming packet. This
55 function is called immediately after initialisation and after
56 the readfn function (below) has returned a packet.
57 sendfn A function that is called on the interrupt to inject bytes out
59 of the interface. If this function returns non-zero then packet
60 at the address returned is freed.
61 readfn A function that is called on the interrupt to read incoming
63 bytes. If the function returns non-zero then a packet is
64 assumed to have been read, with length as returned by readfn and
65 lying at the address specified by packetfn.
66 onlinefn
68 A function that is called when the device is to be turned online
69 offlinefn
71 A function that is called when the device is to be turned off‐
72 line, if the parameter is non-zero then the function should hang
73 up line (if appropriate) otherwise it should just suspend send‐
74 ing and receiving packets.
75 statusfn
77 A function that returns the status of the device. It is envis‐
78 aged that it will return 0 for offline and 1 for online though
79 it may return other values. The value returned is left for the
80 user to understand.
81
84 When the packet is passed to the driver for output a 4 bytes of header
85 space is available at dp-4. The SLIP driver by Dominic Morris utilises
86 these bytes to implement a linked list and to hold the length of the
87 outgoing packet.
88 Other packet drivers might wish to copy the packet to their own address
90 space for converting into other forms - eg CSLIP form. Alternatively
91 they might simply create a link from their own space to the packet in
92 the queue so to reduce time wasted copying bytes.
93
96 Dominic Morris <dom@jb.man.ac.uk>
97 18 February 2000 pktdrive(3z)