/*
 * Copyright (C) ST-Ericsson AB 2010
 * Author:      Sjur Brendeland
 * License terms: GNU General Public License (GPL) version 2
 */

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

#include <linux/stddef.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <asm/unaligned.h>
#include <net/caif/caif_layer.h>
#include <net/caif/cfsrvl.h>
#include <net/caif/cfpkt.h>

#define container_obj(layr) container_of(layr, struct cfrfml, serv.layer)
#define RFM_SEGMENTATION_BIT 0x01
#define RFM_HEAD_SIZE 7

static int cfrfml_receive(struct cflayer *layr, struct cfpkt *pkt);
static int cfrfml_transmit(struct cflayer *layr, struct cfpkt *pkt);

struct cfrfml {
        struct cfsrvl serv;
        struct cfpkt *incomplete_frm;
        int fragment_size;
        u8  seghead[6];
        u16 pdu_size;
        /* Protects serialized processing of packets */
        spinlock_t sync;
};

static void cfrfml_release(struct cflayer *layer)
{
        struct cfsrvl *srvl = container_of(layer, struct cfsrvl, layer);
        struct cfrfml *rfml = container_obj(&srvl->layer);

        if (rfml->incomplete_frm)
                cfpkt_destroy(rfml->incomplete_frm);

        kfree(srvl);
}

struct cflayer *cfrfml_create(u8 channel_id, struct dev_info *dev_info,
                              int mtu_size)
{
        int tmp;
        struct cfrfml *this = kzalloc(sizeof(struct cfrfml), GFP_ATOMIC);

        if (!this)
                return NULL;

        cfsrvl_init(&this->serv, channel_id, dev_info, false);
        this->serv.release = cfrfml_release;
        this->serv.layer.receive = cfrfml_receive;
        this->serv.layer.transmit = cfrfml_transmit;

        /* Round down to closest multiple of 16 */
        tmp = (mtu_size - RFM_HEAD_SIZE - 6) / 16;
        tmp *= 16;

        this->fragment_size = tmp;
        spin_lock_init(&this->sync);
        snprintf(this->serv.layer.name, CAIF_LAYER_NAME_SZ,
                "rfm%d", channel_id);

        return &this->serv.layer;
}

static struct cfpkt *rfm_append(struct cfrfml *rfml, char *seghead,
                                struct cfpkt *pkt, int *err)
{
        struct cfpkt *tmppkt;
        *err = -EPROTO;
        /* n-th but not last segment */

        if (cfpkt_extr_head(pkt, seghead, 6) < 0)
                return NULL;

        /* Verify correct header */
        if (memcmp(seghead, rfml->seghead, 6) != 0)
                return NULL;

        tmppkt = cfpkt_append(rfml->incomplete_frm, pkt,
                        rfml->pdu_size + RFM_HEAD_SIZE);

        /* If cfpkt_append failes input pkts are not freed */
        *err = -ENOMEM;
        if (tmppkt == NULL)
                return NULL;

        *err = 0;
        return tmppkt;
}

static int cfrfml_receive(struct cflayer *layr, struct cfpkt *pkt)
{
        u8 tmp;
        bool segmented;
        int err;
        u8 seghead[6];
        struct cfrfml *rfml;
        struct cfpkt *tmppkt = NULL;

        caif_assert(layr->up != NULL);
        caif_assert(layr->receive != NULL);
        rfml = container_obj(layr);
        spin_lock(&rfml->sync);

        err = -EPROTO;
        if (cfpkt_extr_head(pkt, &tmp, 1) < 0)
                goto out;
        segmented = tmp & RFM_SEGMENTATION_BIT;

        if (segmented) {
                if (rfml->incomplete_frm == NULL) {
                        /* Initial Segment */
                        if (cfpkt_peek_head(pkt, rfml->seghead, 6) < 0)
                                goto out;

                        rfml->pdu_size = get_unaligned_le16(rfml->seghead+4);

                        if (cfpkt_erroneous(pkt))
                                goto out;
                        rfml->incomplete_frm = pkt;
                        pkt = NULL;
                } else {

                        tmppkt = rfm_append(rfml, seghead, pkt, &err);
                        if (tmppkt == NULL)
                                goto out;

                        if (cfpkt_erroneous(tmppkt))
                                goto out;

                        rfml->incomplete_frm = tmppkt;


                        if (cfpkt_erroneous(tmppkt))
                                goto out;
                }
                err = 0;
                goto out;
        }

        if (rfml->incomplete_frm) {

                /* Last Segment */
                tmppkt = rfm_append(rfml, seghead, pkt, &err);
                if (tmppkt == NULL)
                        goto out;

                if (cfpkt_erroneous(tmppkt))
                        goto out;

                rfml->incomplete_frm = NULL;
                pkt = tmppkt;
                tmppkt = NULL;

                /* Verify that length is correct */
                err = EPROTO;
                if (rfml->pdu_size != cfpkt_getlen(pkt) - RFM_HEAD_SIZE + 1)
                        goto out;
        }

        err = rfml->serv.layer.up->receive(rfml->serv.layer.up, pkt);

out:

        if (err != 0) {
                if (tmppkt)
                        cfpkt_destroy(tmppkt);
                if (pkt)
                        cfpkt_destroy(pkt);
                if (rfml->incomplete_frm)
                        cfpkt_destroy(rfml->incomplete_frm);
                rfml->incomplete_frm = NULL;

                pr_info("Connection error %d triggered on RFM link\n", err);

                /* Trigger connection error upon failure.*/
                layr->up->ctrlcmd(layr->up, CAIF_CTRLCMD_REMOTE_SHUTDOWN_IND,
                                        rfml->serv.dev_info.id);
        }
        spin_unlock(&rfml->sync);

        if (unlikely(err == -EAGAIN))
                /* It is not possible to recover after drop of a fragment */
                err = -EIO;

        return err;
}


static int cfrfml_transmit_segment(struct cfrfml *rfml, struct cfpkt *pkt)
{
        caif_assert(cfpkt_getlen(pkt) < rfml->fragment_size + RFM_HEAD_SIZE);

        /* Add info for MUX-layer to route the packet out. */
        cfpkt_info(pkt)->channel_id = rfml->serv.layer.id;

        /*
         * To optimize alignment, we add up the size of CAIF header before
         * payload.
         */
        cfpkt_info(pkt)->hdr_len = RFM_HEAD_SIZE;
        cfpkt_info(pkt)->dev_info = &rfml->serv.dev_info;

        return rfml->serv.layer.dn->transmit(rfml->serv.layer.dn, pkt);
}

static int cfrfml_transmit(struct cflayer *layr, struct cfpkt *pkt)
{
        int err;
        u8 seg;
        u8 head[6];
        struct cfpkt *rearpkt = NULL;
        struct cfpkt *frontpkt = pkt;
        struct cfrfml *rfml = container_obj(layr);

        caif_assert(layr->dn != NULL);
        caif_assert(layr->dn->transmit != NULL);

        if (!cfsrvl_ready(&rfml->serv, &err))
                goto out;

        err = -EPROTO;
        if (cfpkt_getlen(pkt) <= RFM_HEAD_SIZE-1)
                goto out;

        err = 0;
        if (cfpkt_getlen(pkt) > rfml->fragment_size + RFM_HEAD_SIZE)
                err = cfpkt_peek_head(pkt, head, 6);

        if (err < 0)
                goto out;

        while (cfpkt_getlen(frontpkt) > rfml->fragment_size + RFM_HEAD_SIZE) {

                seg = 1;
                err = -EPROTO;

                if (cfpkt_add_head(frontpkt, &seg, 1) < 0)
                        goto out;
                /*
                 * On OOM error cfpkt_split returns NULL.
                 *
                 * NOTE: Segmented pdu is not correctly aligned.
                 * This has negative performance impact.
                 */

                rearpkt = cfpkt_split(frontpkt, rfml->fragment_size);
                if (rearpkt == NULL)
                        goto out;

                err = cfrfml_transmit_segment(rfml, frontpkt);

                if (err != 0) {
                        frontpkt = NULL;
                        goto out;
                }

                frontpkt = rearpkt;
                rearpkt = NULL;

                err = -ENOMEM;
                if (frontpkt == NULL)
                        goto out;
                err = -EPROTO;
                if (cfpkt_add_head(frontpkt, head, 6) < 0)
                        goto out;

        }

        seg = 0;
        err = -EPROTO;

        if (cfpkt_add_head(frontpkt, &seg, 1) < 0)
                goto out;

        err = cfrfml_transmit_segment(rfml, frontpkt);

        frontpkt = NULL;
out:

        if (err != 0) {
                pr_info("Connection error %d triggered on RFM link\n", err);
                /* Trigger connection error upon failure.*/

                layr->up->ctrlcmd(layr->up, CAIF_CTRLCMD_REMOTE_SHUTDOWN_IND,
                                        rfml->serv.dev_info.id);

                if (rearpkt)
                        cfpkt_destroy(rearpkt);

                if (frontpkt)
                        cfpkt_destroy(frontpkt);
        }

        return err;
}