linux/net/caif/cfserl.c
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   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
  21struct 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
  29static int cfserl_receive(struct cflayer *layr, struct cfpkt *pkt);
  30static int cfserl_transmit(struct cflayer *layr, struct cfpkt *pkt);
  31static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
  32                                int phyid);
  33
  34struct 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
  49static 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
 175static 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
 184static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
 185                                int phyid)
 186{
 187        layr->up->ctrlcmd(layr->up, ctrl, phyid);
 188}
 189
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