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 = kmalloc(sizeof(struct cfserl), GFP_ATOMIC);
  37         if (!this) {
  38                 pr_warn("Out of memory\n");
  39                 return NULL;
  40         }
  41         caif_assert(offsetof(struct cfserl, layer) == 0);
  42         memset(this, 0, sizeof(struct cfserl));
  43         this->layer.receive = cfserl_receive;
  44         this->layer.transmit = cfserl_transmit;
  45         this->layer.ctrlcmd = cfserl_ctrlcmd;
  46         this->layer.type = type;
  47         this->usestx = use_stx;
  48         spin_lock_init(&this->sync);
  49         snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
  50         return &this->layer;
  51 }
  52
  53 static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
  54 {
  55         struct cfserl *layr = container_obj(l);
  56         u16 pkt_len;
  57         struct cfpkt *pkt = NULL;
  58         struct cfpkt *tail_pkt = NULL;
  59         u8 tmp8;
  60         u16 tmp;
  61         u8 stx = CFSERL_STX;
  62         int ret;
  63         u16 expectlen = 0;
  64
  65         caif_assert(newpkt != NULL);
  66         spin_lock(&layr->sync);
  67
  68         if (layr->incomplete_frm != NULL) {
  69                 layr->incomplete_frm =
  70                     cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
  71                 pkt = layr->incomplete_frm;
  72                 if (pkt == NULL) {
  73                         spin_unlock(&layr->sync);
  74                         return -ENOMEM;
  75                 }
  76         } else {
  77                 pkt = newpkt;
  78         }
  79         layr->incomplete_frm = NULL;
  80
  81         do {
  82                 /* Search for STX at start of pkt if STX is used */
  83                 if (layr->usestx) {
  84                         cfpkt_extr_head(pkt, &tmp8, 1);
  85                         if (tmp8 != CFSERL_STX) {
  86                                 while (cfpkt_more(pkt)
  87                                        && tmp8 != CFSERL_STX) {
  88                                         cfpkt_extr_head(pkt, &tmp8, 1);
  89                                 }
  90                                 if (!cfpkt_more(pkt)) {
  91                                         cfpkt_destroy(pkt);
  92                                         layr->incomplete_frm = NULL;
  93                                         spin_unlock(&layr->sync);
  94                                         return -EPROTO;
  95                                 }
  96                         }
  97                 }
  98
  99                 pkt_len = cfpkt_getlen(pkt);
 100
 101                 /*
 102                  *  pkt_len is the accumulated length of the packet data
 103                  *  we have received so far.
 104                  *  Exit if frame doesn't hold length.
 105                  */
 106
 107                 if (pkt_len < 2) {
 108                         if (layr->usestx)
 109                                 cfpkt_add_head(pkt, &stx, 1);
 110                         layr->incomplete_frm = pkt;
 111                         spin_unlock(&layr->sync);
 112                         return 0;
 113                 }
 114
 115                 /*
 116                  *  Find length of frame.
 117                  *  expectlen is the length we need for a full frame.
 118                  */
 119                 cfpkt_peek_head(pkt, &tmp, 2);
 120                 expectlen = le16_to_cpu(tmp) + 2;
 121                 /*
 122                  * Frame error handling
 123                  */
 124                 if (expectlen < SERIAL_MINIUM_PACKET_SIZE
 125                     || expectlen > SERIAL_MAX_FRAMESIZE) {
 126                         if (!layr->usestx) {
 127                                 if (pkt != NULL)
 128                                         cfpkt_destroy(pkt);
 129                                 layr->incomplete_frm = NULL;
 130                                 expectlen = 0;
 131                                 spin_unlock(&layr->sync);
 132                                 return -EPROTO;
 133                         }
 134                         continue;
 135                 }
 136
 137                 if (pkt_len < expectlen) {
 138                         /* Too little received data */
 139                         if (layr->usestx)
 140                                 cfpkt_add_head(pkt, &stx, 1);
 141                         layr->incomplete_frm = pkt;
 142                         spin_unlock(&layr->sync);
 143                         return 0;
 144                 }
 145
 146                 /*
 147                  * Enough data for at least one frame.
 148                  * Split the frame, if too long
 149                  */
 150                 if (pkt_len > expectlen)
 151                         tail_pkt = cfpkt_split(pkt, expectlen);
 152                 else
 153                         tail_pkt = NULL;
 154
 155                 /* Send the first part of packet upwards.*/
 156                 spin_unlock(&layr->sync);
 157                 ret = layr->layer.up->receive(layr->layer.up, pkt);
 158                 spin_lock(&layr->sync);
 159                 if (ret == -EILSEQ) {
 160                         if (layr->usestx) {
 161                                 if (tail_pkt != NULL)
 162                                         pkt = cfpkt_append(pkt, tail_pkt, 0);
 163                                 /* Start search for next STX if frame failed */
 164                                 continue;
 165                         } else {
 166                                 cfpkt_destroy(pkt);
 167                                 pkt = NULL;
 168                         }
 169                 }
 170
 171                 pkt = tail_pkt;
 172
 173         } while (pkt != NULL);
 174
 175         spin_unlock(&layr->sync);
 176         return 0;
 177 }
 178
 179 static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
 180 {
 181         struct cfserl *layr = container_obj(layer);
 182         u8 tmp8 = CFSERL_STX;
 183         if (layr->usestx)
 184                 cfpkt_add_head(newpkt, &tmp8, 1);
 185         return layer->dn->transmit(layer->dn, newpkt);
 186 }
 187
 188 static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
 189                                 int phyid)
 190 {
 191         layr->up->ctrlcmd(layr->up, ctrl, phyid);
 192 }