// 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/cfsrvl.h>
#include <net/caif/cfpkt.h>


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

#define DGM_CMD_BIT  0x80
#define DGM_FLOW_OFF 0x81
#define DGM_FLOW_ON  0x80
#define DGM_MTU 1500

static int cfdgml_receive(struct cflayer *layr, struct cfpkt *pkt);
static int cfdgml_transmit(struct cflayer *layr, struct cfpkt *pkt);

struct cflayer *cfdgml_create(u8 channel_id, struct dev_info *dev_info)
{
        struct cfsrvl *dgm = kzalloc_obj(struct cfsrvl, GFP_ATOMIC);
        if (!dgm)
                return NULL;
        caif_assert(offsetof(struct cfsrvl, layer) == 0);
        cfsrvl_init(dgm, channel_id, dev_info, true);
        dgm->layer.receive = cfdgml_receive;
        dgm->layer.transmit = cfdgml_transmit;
        snprintf(dgm->layer.name, CAIF_LAYER_NAME_SZ, "dgm%d", channel_id);
        return &dgm->layer;
}

static int cfdgml_receive(struct cflayer *layr, struct cfpkt *pkt)
{
        u8 cmd = -1;
        u8 dgmhdr[3];
        int ret;
        caif_assert(layr->up != NULL);
        caif_assert(layr->receive != NULL);
        caif_assert(layr->ctrlcmd != NULL);

        if (cfpkt_extr_head(pkt, &cmd, 1) < 0) {
                pr_err("Packet is erroneous!\n");
                cfpkt_destroy(pkt);
                return -EPROTO;
        }

        if ((cmd & DGM_CMD_BIT) == 0) {
                if (cfpkt_extr_head(pkt, &dgmhdr, 3) < 0) {
                        pr_err("Packet is erroneous!\n");
                        cfpkt_destroy(pkt);
                        return -EPROTO;
                }
                ret = layr->up->receive(layr->up, pkt);
                return ret;
        }

        switch (cmd) {
        case DGM_FLOW_OFF:      /* FLOW OFF */
                layr->ctrlcmd(layr, CAIF_CTRLCMD_FLOW_OFF_IND, 0);
                cfpkt_destroy(pkt);
                return 0;
        case DGM_FLOW_ON:       /* FLOW ON */
                layr->ctrlcmd(layr, CAIF_CTRLCMD_FLOW_ON_IND, 0);
                cfpkt_destroy(pkt);
                return 0;
        default:
                cfpkt_destroy(pkt);
                pr_info("Unknown datagram control %d (0x%x)\n", cmd, cmd);
                return -EPROTO;
        }
}

static int cfdgml_transmit(struct cflayer *layr, struct cfpkt *pkt)
{
        u8 packet_type;
        u32 zero = 0;
        struct caif_payload_info *info;
        struct cfsrvl *service = container_obj(layr);
        int ret;

        if (!cfsrvl_ready(service, &ret)) {
                cfpkt_destroy(pkt);
                return ret;
        }

        /* STE Modem cannot handle more than 1500 bytes datagrams */
        if (cfpkt_getlen(pkt) > DGM_MTU) {
                cfpkt_destroy(pkt);
                return -EMSGSIZE;
        }

        cfpkt_add_head(pkt, &zero, 3);
        packet_type = 0x08; /* B9 set - UNCLASSIFIED */
        cfpkt_add_head(pkt, &packet_type, 1);

        /* Add info for MUX-layer to route the packet out. */
        info = cfpkt_info(pkt);
        info->channel_id = service->layer.id;
        /* To optimize alignment, we add up the size of CAIF header
         * before payload.
         */
        info->hdr_len = 4;
        info->dev_info = &service->dev_info;
        return layr->dn->transmit(layr->dn, pkt);
}