// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) ST-Ericsson AB 2010
 * Author:      Sjur Brendeland
 */

#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

#include <linux/stddef.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <net/caif/caif_layer.h>
#include <net/caif/cfpkt.h>
#include <net/caif/cfserl.h>

#define container_obj(layr) ((struct cfserl *) layr)

#define CFSERL_STX 0x02
#define SERIAL_MINIUM_PACKET_SIZE 4
#define SERIAL_MAX_FRAMESIZE 4096
struct cfserl {
        struct cflayer layer;
        struct cfpkt *incomplete_frm;
        /* Protects parallel processing of incoming packets */
        spinlock_t sync;
        bool usestx;
};

static int cfserl_receive(struct cflayer *layr, struct cfpkt *pkt);
static int cfserl_transmit(struct cflayer *layr, struct cfpkt *pkt);
static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
                           int phyid);

void cfserl_release(struct cflayer *layer)
{
        kfree(layer);
}

struct cflayer *cfserl_create(int instance, bool use_stx)
{
        struct cfserl *this = kzalloc_obj(struct cfserl, GFP_ATOMIC);
        if (!this)
                return NULL;
        caif_assert(offsetof(struct cfserl, layer) == 0);
        this->layer.receive = cfserl_receive;
        this->layer.transmit = cfserl_transmit;
        this->layer.ctrlcmd = cfserl_ctrlcmd;
        this->usestx = use_stx;
        spin_lock_init(&this->sync);
        snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
        return &this->layer;
}

static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
{
        struct cfserl *layr = container_obj(l);
        u16 pkt_len;
        struct cfpkt *pkt = NULL;
        struct cfpkt *tail_pkt = NULL;
        u8 tmp8;
        u16 tmp;
        u8 stx = CFSERL_STX;
        int ret;
        u16 expectlen = 0;

        caif_assert(newpkt != NULL);
        spin_lock(&layr->sync);

        if (layr->incomplete_frm != NULL) {
                layr->incomplete_frm =
                    cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
                pkt = layr->incomplete_frm;
                if (pkt == NULL) {
                        spin_unlock(&layr->sync);
                        return -ENOMEM;
                }
        } else {
                pkt = newpkt;
        }
        layr->incomplete_frm = NULL;

        do {
                /* Search for STX at start of pkt if STX is used */
                if (layr->usestx) {
                        cfpkt_extr_head(pkt, &tmp8, 1);
                        if (tmp8 != CFSERL_STX) {
                                while (cfpkt_more(pkt)
                                       && tmp8 != CFSERL_STX) {
                                        cfpkt_extr_head(pkt, &tmp8, 1);
                                }
                                if (!cfpkt_more(pkt)) {
                                        cfpkt_destroy(pkt);
                                        layr->incomplete_frm = NULL;
                                        spin_unlock(&layr->sync);
                                        return -EPROTO;
                                }
                        }
                }

                pkt_len = cfpkt_getlen(pkt);

                /*
                 *  pkt_len is the accumulated length of the packet data
                 *  we have received so far.
                 *  Exit if frame doesn't hold length.
                 */

                if (pkt_len < 2) {
                        if (layr->usestx)
                                cfpkt_add_head(pkt, &stx, 1);
                        layr->incomplete_frm = pkt;
                        spin_unlock(&layr->sync);
                        return 0;
                }

                /*
                 *  Find length of frame.
                 *  expectlen is the length we need for a full frame.
                 */
                cfpkt_peek_head(pkt, &tmp, 2);
                expectlen = le16_to_cpu(tmp) + 2;
                /*
                 * Frame error handling
                 */
                if (expectlen < SERIAL_MINIUM_PACKET_SIZE
                    || expectlen > SERIAL_MAX_FRAMESIZE) {
                        if (!layr->usestx) {
                                if (pkt != NULL)
                                        cfpkt_destroy(pkt);
                                layr->incomplete_frm = NULL;
                                spin_unlock(&layr->sync);
                                return -EPROTO;
                        }
                        continue;
                }

                if (pkt_len < expectlen) {
                        /* Too little received data */
                        if (layr->usestx)
                                cfpkt_add_head(pkt, &stx, 1);
                        layr->incomplete_frm = pkt;
                        spin_unlock(&layr->sync);
                        return 0;
                }

                /*
                 * Enough data for at least one frame.
                 * Split the frame, if too long
                 */
                if (pkt_len > expectlen)
                        tail_pkt = cfpkt_split(pkt, expectlen);
                else
                        tail_pkt = NULL;

                /* Send the first part of packet upwards.*/
                spin_unlock(&layr->sync);
                ret = layr->layer.up->receive(layr->layer.up, pkt);
                spin_lock(&layr->sync);
                if (ret == -EILSEQ) {
                        if (layr->usestx) {
                                if (tail_pkt != NULL)
                                        pkt = cfpkt_append(pkt, tail_pkt, 0);
                                /* Start search for next STX if frame failed */
                                continue;
                        } else {
                                cfpkt_destroy(pkt);
                                pkt = NULL;
                        }
                }

                pkt = tail_pkt;

        } while (pkt != NULL);

        spin_unlock(&layr->sync);
        return 0;
}

static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
{
        struct cfserl *layr = container_obj(layer);
        u8 tmp8 = CFSERL_STX;
        if (layr->usestx)
                cfpkt_add_head(newpkt, &tmp8, 1);
        return layer->dn->transmit(layer->dn, newpkt);
}

static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
                           int phyid)
{
        layr->up->ctrlcmd(layr->up, ctrl, phyid);
}