1 /*
2 ** File: netbuff.c Jun. 10, 2000
3 **
4 ** Author: Giovanni Falzoni <gfalzoni@inwind.it>
5 **
6 ** This file contains specific implementation of buffering
7 ** for network packets.
8 */
9
10 #include <minix/drivers.h>
11 #include <minix/netdriver.h>
12 #include "dp.h"
13
14 #if (HAVE_BUFFERS == 1)
15
16 static m_hdr_t *allocptr = NULL;
17 static char tx_rx_buff[8192];
18
19 /*
20 ** Name: alloc_buff
21 ** Function: Allocates a buffer from the common pool.
22 */
alloc_buff(dpeth_t * dep,int size)23 void *alloc_buff(dpeth_t *dep, int size)
24 {
25 m_hdr_t *ptr, *wrk = allocptr;
26 int units = ((size + sizeof(m_hdr_t) - 1) / sizeof(m_hdr_t)) + 1;
27
28 for (ptr = wrk->next;; wrk = ptr, ptr = ptr->next) {
29 if (ptr->size >= units) {
30 /* Memory is available, carve requested size from pool */
31 if (ptr->size == units) {
32 wrk->next = ptr->next;
33 } else {
34 /* Get memory from top address */
35 ptr->size -= units;
36 ptr += ptr->size;
37 ptr->size = units;
38 }
39 allocptr = wrk;
40 return ptr + 1;
41 }
42 if (ptr == allocptr) break;
43 }
44 return NULL; /* No memory available */
45 }
46
47 /*
48 ** Name: free_buff
49 ** Function: Returns a buffer to the common pool.
50 */
free_buff(dpeth_t * dep,void * blk)51 void free_buff(dpeth_t *dep, void *blk)
52 {
53 m_hdr_t *wrk, *ptr = (m_hdr_t *) blk - 1;
54
55 /* Scan linked list for the correct place */
56 for (wrk = allocptr; !(ptr > wrk && ptr < wrk->next); wrk = wrk->next)
57 if (wrk >= wrk->next && (ptr > wrk || ptr < wrk->next)) break;
58
59 /* Check if adjacent block is free and join blocks */
60 if (ptr + ptr->size == wrk->next) {
61 ptr->size += wrk->next->size;
62 ptr->next = wrk->next->next;
63 } else
64 ptr->next = wrk->next;
65 if (wrk + wrk->size == ptr) {
66 wrk->size += ptr->size;
67 wrk->next = ptr->next;
68 } else
69 wrk->next = ptr;
70 allocptr = wrk; /* Point allocptr to block just released */
71 }
72
73 /*
74 ** Name: init_buff
75 ** Function: Initalizes driver data structures.
76 */
init_buff(dpeth_t * dep,buff_t ** tx_buff)77 void init_buff(dpeth_t *dep, buff_t **tx_buff)
78 {
79
80 /* Initializes buffer pool */
81 if (allocptr == NULL) {
82 m_hdr_t *rx = (m_hdr_t *) tx_rx_buff;
83 rx->next = allocptr = rx;
84 rx->size = 0;
85 rx += 1;
86 rx->next = NULL;
87 rx->size = (sizeof(tx_rx_buff) / sizeof(m_hdr_t)) - 1;
88 free_buff(dep, rx + 1);
89 dep->de_recvq_tail = dep->de_recvq_head = NULL;
90 if (tx_buff != NULL) {
91 *tx_buff = alloc_buff(dep,
92 NDEV_ETH_PACKET_MAX + sizeof(buff_t));
93 (*tx_buff)->size = 0;
94 }
95 }
96 }
97
98 #endif /* HAVE_BUFFERS */
99
100 /** netbuff.c **/
101