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cfserl.c
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1 /*
2  * Copyright (C) ST-Ericsson AB 2010
3  * Author: Sjur Brendeland/[email protected]
4  * License terms: GNU General Public License (GPL) version 2
5  */
6 
7 #define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__
8 
9 #include <linux/stddef.h>
10 #include <linux/spinlock.h>
11 #include <linux/slab.h>
12 #include <net/caif/caif_layer.h>
13 #include <net/caif/cfpkt.h>
14 #include <net/caif/cfserl.h>
15 
16 #define container_obj(layr) ((struct cfserl *) layr)
17 
18 #define CFSERL_STX 0x02
19 #define SERIAL_MINIUM_PACKET_SIZE 4
20 #define SERIAL_MAX_FRAMESIZE 4096
21 struct cfserl {
22  struct cflayer layer;
24  /* Protects parallel processing of incoming packets */
26  bool usestx;
27 };
28 
29 static int cfserl_receive(struct cflayer *layr, struct cfpkt *pkt);
30 static int cfserl_transmit(struct cflayer *layr, struct cfpkt *pkt);
31 static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
32  int phyid);
33 
34 struct cflayer *cfserl_create(int instance, bool use_stx)
35 {
36  struct cfserl *this = kzalloc(sizeof(struct cfserl), GFP_ATOMIC);
37  if (!this)
38  return NULL;
39  caif_assert(offsetof(struct cfserl, layer) == 0);
40  this->layer.receive = cfserl_receive;
41  this->layer.transmit = cfserl_transmit;
42  this->layer.ctrlcmd = cfserl_ctrlcmd;
43  this->usestx = use_stx;
44  spin_lock_init(&this->sync);
45  snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
46  return &this->layer;
47 }
48 
49 static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
50 {
51  struct cfserl *layr = container_obj(l);
52  u16 pkt_len;
53  struct cfpkt *pkt = NULL;
54  struct cfpkt *tail_pkt = NULL;
55  u8 tmp8;
56  u16 tmp;
57  u8 stx = CFSERL_STX;
58  int ret;
59  u16 expectlen = 0;
60 
61  caif_assert(newpkt != NULL);
62  spin_lock(&layr->sync);
63 
64  if (layr->incomplete_frm != NULL) {
65  layr->incomplete_frm =
66  cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
67  pkt = layr->incomplete_frm;
68  if (pkt == NULL) {
69  spin_unlock(&layr->sync);
70  return -ENOMEM;
71  }
72  } else {
73  pkt = newpkt;
74  }
75  layr->incomplete_frm = NULL;
76 
77  do {
78  /* Search for STX at start of pkt if STX is used */
79  if (layr->usestx) {
80  cfpkt_extr_head(pkt, &tmp8, 1);
81  if (tmp8 != CFSERL_STX) {
82  while (cfpkt_more(pkt)
83  && tmp8 != CFSERL_STX) {
84  cfpkt_extr_head(pkt, &tmp8, 1);
85  }
86  if (!cfpkt_more(pkt)) {
87  cfpkt_destroy(pkt);
88  layr->incomplete_frm = NULL;
89  spin_unlock(&layr->sync);
90  return -EPROTO;
91  }
92  }
93  }
94 
95  pkt_len = cfpkt_getlen(pkt);
96 
97  /*
98  * pkt_len is the accumulated length of the packet data
99  * we have received so far.
100  * Exit if frame doesn't hold length.
101  */
102 
103  if (pkt_len < 2) {
104  if (layr->usestx)
105  cfpkt_add_head(pkt, &stx, 1);
106  layr->incomplete_frm = pkt;
107  spin_unlock(&layr->sync);
108  return 0;
109  }
110 
111  /*
112  * Find length of frame.
113  * expectlen is the length we need for a full frame.
114  */
115  cfpkt_peek_head(pkt, &tmp, 2);
116  expectlen = le16_to_cpu(tmp) + 2;
117  /*
118  * Frame error handling
119  */
120  if (expectlen < SERIAL_MINIUM_PACKET_SIZE
121  || expectlen > SERIAL_MAX_FRAMESIZE) {
122  if (!layr->usestx) {
123  if (pkt != NULL)
124  cfpkt_destroy(pkt);
125  layr->incomplete_frm = NULL;
126  expectlen = 0;
127  spin_unlock(&layr->sync);
128  return -EPROTO;
129  }
130  continue;
131  }
132 
133  if (pkt_len < expectlen) {
134  /* Too little received data */
135  if (layr->usestx)
136  cfpkt_add_head(pkt, &stx, 1);
137  layr->incomplete_frm = pkt;
138  spin_unlock(&layr->sync);
139  return 0;
140  }
141 
142  /*
143  * Enough data for at least one frame.
144  * Split the frame, if too long
145  */
146  if (pkt_len > expectlen)
147  tail_pkt = cfpkt_split(pkt, expectlen);
148  else
149  tail_pkt = NULL;
150 
151  /* Send the first part of packet upwards.*/
152  spin_unlock(&layr->sync);
153  ret = layr->layer.up->receive(layr->layer.up, pkt);
154  spin_lock(&layr->sync);
155  if (ret == -EILSEQ) {
156  if (layr->usestx) {
157  if (tail_pkt != NULL)
158  pkt = cfpkt_append(pkt, tail_pkt, 0);
159  /* Start search for next STX if frame failed */
160  continue;
161  } else {
162  cfpkt_destroy(pkt);
163  pkt = NULL;
164  }
165  }
166 
167  pkt = tail_pkt;
168 
169  } while (pkt != NULL);
170 
171  spin_unlock(&layr->sync);
172  return 0;
173 }
174 
175 static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
176 {
177  struct cfserl *layr = container_obj(layer);
178  u8 tmp8 = CFSERL_STX;
179  if (layr->usestx)
180  cfpkt_add_head(newpkt, &tmp8, 1);
181  return layer->dn->transmit(layer->dn, newpkt);
182 }
183 
184 static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
185  int phyid)
186 {
187  layr->up->ctrlcmd(layr->up, ctrl, phyid);
188 }