net/caif/cfserl.c

   1 /*
   2  * Copyright (C) ST-Ericsson AB 2010
   3  * Author:      Sjur Brendeland/sjur.brandeland@stericsson.com
   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;
  23         struct cfpkt *incomplete_frm;
  24         /* Protects parallel processing of incoming packets */
  25         spinlock_t sync;
  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 type, 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->layer.type = type;
  44         this->usestx = use_stx;
  45         spin_lock_init(&this->sync);
  46         snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
  47         return &this->layer;
  48 }
  49
  50 static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
  51 {
  52         struct cfserl *layr = container_obj(l);
  53         u16 pkt_len;
  54         struct cfpkt *pkt = NULL;
  55         struct cfpkt *tail_pkt = NULL;
  56         u8 tmp8;
  57         u16 tmp;
  58         u8 stx = CFSERL_STX;
  59         int ret;
  60         u16 expectlen = 0;
  61
  62         caif_assert(newpkt != NULL);
  63         spin_lock(&layr->sync);
  64
  65         if (layr->incomplete_frm != NULL) {
  66                 layr->incomplete_frm =
  67                     cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
  68                 pkt = layr->incomplete_frm;
  69                 if (pkt == NULL) {
  70                         spin_unlock(&layr->sync);
  71                         return -ENOMEM;
  72                 }
  73         } else {
  74                 pkt = newpkt;
  75         }
  76         layr->incomplete_frm = NULL;
  77
  78         do {
  79                 /* Search for STX at start of pkt if STX is used */
  80                 if (layr->usestx) {
  81                         cfpkt_extr_head(pkt, &tmp8, 1);
  82                         if (tmp8 != CFSERL_STX) {
  83                                 while (cfpkt_more(pkt)
  84                                        && tmp8 != CFSERL_STX) {
  85                                         cfpkt_extr_head(pkt, &tmp8, 1);
  86                                 }
  87                                 if (!cfpkt_more(pkt)) {
  88                                         cfpkt_destroy(pkt);
  89                                         layr->incomplete_frm = NULL;
  90                                         spin_unlock(&layr->sync);
  91                                         return -EPROTO;
  92                                 }
  93                         }
  94                 }
  95
  96                 pkt_len = cfpkt_getlen(pkt);
  97
  98                 /*
  99                  *  pkt_len is the accumulated length of the packet data
 100                  *  we have received so far.
 101                  *  Exit if frame doesn't hold length.
 102                  */
 103
 104                 if (pkt_len < 2) {
 105                         if (layr->usestx)
 106                                 cfpkt_add_head(pkt, &stx, 1);
 107                         layr->incomplete_frm = pkt;
 108                         spin_unlock(&layr->sync);
 109                         return 0;
 110                 }
 111
 112                 /*
 113                  *  Find length of frame.
 114                  *  expectlen is the length we need for a full frame.
 115                  */
 116                 cfpkt_peek_head(pkt, &tmp, 2);
 117                 expectlen = le16_to_cpu(tmp) + 2;
 118                 /*
 119                  * Frame error handling
 120                  */
 121                 if (expectlen < SERIAL_MINIUM_PACKET_SIZE
 122                     || expectlen > SERIAL_MAX_FRAMESIZE) {
 123                         if (!layr->usestx) {
 124                                 if (pkt != NULL)
 125                                         cfpkt_destroy(pkt);
 126                                 layr->incomplete_frm = NULL;
 127                                 expectlen = 0;
 128                                 spin_unlock(&layr->sync);
 129                                 return -EPROTO;
 130                         }
 131                         continue;
 132                 }
 133
 134                 if (pkt_len < expectlen) {
 135                         /* Too little received data */
 136                         if (layr->usestx)
 137                                 cfpkt_add_head(pkt, &stx, 1);
 138                         layr->incomplete_frm = pkt;
 139                         spin_unlock(&layr->sync);
 140                         return 0;
 141                 }
 142
 143                 /*
 144                  * Enough data for at least one frame.
 145                  * Split the frame, if too long
 146                  */
 147                 if (pkt_len > expectlen)
 148                         tail_pkt = cfpkt_split(pkt, expectlen);
 149                 else
 150                         tail_pkt = NULL;
 151
 152                 /* Send the first part of packet upwards.*/
 153                 spin_unlock(&layr->sync);
 154                 ret = layr->layer.up->receive(layr->layer.up, pkt);
 155                 spin_lock(&layr->sync);
 156                 if (ret == -EILSEQ) {
 157                         if (layr->usestx) {
 158                                 if (tail_pkt != NULL)
 159                                         pkt = cfpkt_append(pkt, tail_pkt, 0);
 160                                 /* Start search for next STX if frame failed */
 161                                 continue;
 162                         } else {
 163                                 cfpkt_destroy(pkt);
 164                                 pkt = NULL;
 165                         }
 166                 }
 167
 168                 pkt = tail_pkt;
 169
 170         } while (pkt != NULL);
 171
 172         spin_unlock(&layr->sync);
 173         return 0;
 174 }
 175
 176 static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
 177 {
 178         struct cfserl *layr = container_obj(layer);
 179         u8 tmp8 = CFSERL_STX;
 180         if (layr->usestx)
 181                 cfpkt_add_head(newpkt, &tmp8, 1);
 182         return layer->dn->transmit(layer->dn, newpkt);
 183 }
 184
 185 static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
 186                                 int phyid)
 187 {
 188         layr->up->ctrlcmd(layr->up, ctrl, phyid);
 189 }