// 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 <linux/rculist.h>
#include <net/caif/cfpkt.h>
#include <net/caif/cfmuxl.h>
#include <net/caif/cfsrvl.h>
#include <net/caif/cffrml.h>

#define container_obj(layr) container_of(layr, struct cfmuxl, layer)

#define CAIF_CTRL_CHANNEL 0
#define UP_CACHE_SIZE 8
#define DN_CACHE_SIZE 8

struct cfmuxl {
        struct cflayer layer;
        struct list_head srvl_list;
        struct list_head frml_list;
        struct cflayer *up_cache[UP_CACHE_SIZE];
        struct cflayer *dn_cache[DN_CACHE_SIZE];
        /*
         * Set when inserting or removing downwards layers.
         */
        spinlock_t transmit_lock;

        /*
         * Set when inserting or removing upwards layers.
         */
        spinlock_t receive_lock;

};

static int cfmuxl_receive(struct cflayer *layr, struct cfpkt *pkt);
static int cfmuxl_transmit(struct cflayer *layr, struct cfpkt *pkt);
static void cfmuxl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
                           int phyid);
static struct cflayer *get_up(struct cfmuxl *muxl, u16 id);

struct cflayer *cfmuxl_create(void)
{
        struct cfmuxl *this = kzalloc_obj(struct cfmuxl, GFP_ATOMIC);

        if (!this)
                return NULL;
        this->layer.receive = cfmuxl_receive;
        this->layer.transmit = cfmuxl_transmit;
        this->layer.ctrlcmd = cfmuxl_ctrlcmd;
        INIT_LIST_HEAD(&this->srvl_list);
        INIT_LIST_HEAD(&this->frml_list);
        spin_lock_init(&this->transmit_lock);
        spin_lock_init(&this->receive_lock);
        snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "mux");
        return &this->layer;
}

int cfmuxl_set_dnlayer(struct cflayer *layr, struct cflayer *dn, u8 phyid)
{
        struct cfmuxl *muxl = (struct cfmuxl *) layr;

        spin_lock_bh(&muxl->transmit_lock);
        list_add_rcu(&dn->node, &muxl->frml_list);
        spin_unlock_bh(&muxl->transmit_lock);
        return 0;
}

static struct cflayer *get_from_id(struct list_head *list, u16 id)
{
        struct cflayer *lyr;
        list_for_each_entry_rcu(lyr, list, node) {
                if (lyr->id == id)
                        return lyr;
        }

        return NULL;
}

int cfmuxl_set_uplayer(struct cflayer *layr, struct cflayer *up, u8 linkid)
{
        struct cfmuxl *muxl = container_obj(layr);
        struct cflayer *old;

        spin_lock_bh(&muxl->receive_lock);

        /* Two entries with same id is wrong, so remove old layer from mux */
        old = get_from_id(&muxl->srvl_list, linkid);
        if (old != NULL)
                list_del_rcu(&old->node);

        list_add_rcu(&up->node, &muxl->srvl_list);
        spin_unlock_bh(&muxl->receive_lock);

        return 0;
}

struct cflayer *cfmuxl_remove_dnlayer(struct cflayer *layr, u8 phyid)
{
        struct cfmuxl *muxl = container_obj(layr);
        struct cflayer *dn;
        int idx = phyid % DN_CACHE_SIZE;

        spin_lock_bh(&muxl->transmit_lock);
        RCU_INIT_POINTER(muxl->dn_cache[idx], NULL);
        dn = get_from_id(&muxl->frml_list, phyid);
        if (dn == NULL)
                goto out;

        list_del_rcu(&dn->node);
        caif_assert(dn != NULL);
out:
        spin_unlock_bh(&muxl->transmit_lock);
        return dn;
}

static struct cflayer *get_up(struct cfmuxl *muxl, u16 id)
{
        struct cflayer *up;
        int idx = id % UP_CACHE_SIZE;
        up = rcu_dereference(muxl->up_cache[idx]);
        if (up == NULL || up->id != id) {
                spin_lock_bh(&muxl->receive_lock);
                up = get_from_id(&muxl->srvl_list, id);
                rcu_assign_pointer(muxl->up_cache[idx], up);
                spin_unlock_bh(&muxl->receive_lock);
        }
        return up;
}

static struct cflayer *get_dn(struct cfmuxl *muxl, struct dev_info *dev_info)
{
        struct cflayer *dn;
        int idx = dev_info->id % DN_CACHE_SIZE;
        dn = rcu_dereference(muxl->dn_cache[idx]);
        if (dn == NULL || dn->id != dev_info->id) {
                spin_lock_bh(&muxl->transmit_lock);
                dn = get_from_id(&muxl->frml_list, dev_info->id);
                rcu_assign_pointer(muxl->dn_cache[idx], dn);
                spin_unlock_bh(&muxl->transmit_lock);
        }
        return dn;
}

struct cflayer *cfmuxl_remove_uplayer(struct cflayer *layr, u8 id)
{
        struct cflayer *up;
        struct cfmuxl *muxl = container_obj(layr);
        int idx = id % UP_CACHE_SIZE;

        if (id == 0) {
                pr_warn("Trying to remove control layer\n");
                return NULL;
        }

        spin_lock_bh(&muxl->receive_lock);
        up = get_from_id(&muxl->srvl_list, id);
        if (up == NULL)
                goto out;

        RCU_INIT_POINTER(muxl->up_cache[idx], NULL);
        list_del_rcu(&up->node);
out:
        spin_unlock_bh(&muxl->receive_lock);
        return up;
}

static int cfmuxl_receive(struct cflayer *layr, struct cfpkt *pkt)
{
        int ret;
        struct cfmuxl *muxl = container_obj(layr);
        u8 id;
        struct cflayer *up;
        if (cfpkt_extr_head(pkt, &id, 1) < 0) {
                pr_err("erroneous Caif Packet\n");
                cfpkt_destroy(pkt);
                return -EPROTO;
        }
        rcu_read_lock();
        up = get_up(muxl, id);

        if (up == NULL) {
                pr_debug("Received data on unknown link ID = %d (0x%x)"
                        " up == NULL", id, id);
                cfpkt_destroy(pkt);
                /*
                 * Don't return ERROR, since modem misbehaves and sends out
                 * flow on before linksetup response.
                 */

                rcu_read_unlock();
                return /* CFGLU_EPROT; */ 0;
        }

        /* We can't hold rcu_lock during receive, so take a ref count instead */
        cfsrvl_get(up);
        rcu_read_unlock();

        ret = up->receive(up, pkt);

        cfsrvl_put(up);
        return ret;
}

static int cfmuxl_transmit(struct cflayer *layr, struct cfpkt *pkt)
{
        struct cfmuxl *muxl = container_obj(layr);
        int err;
        u8 linkid;
        struct cflayer *dn;
        struct caif_payload_info *info = cfpkt_info(pkt);
        BUG_ON(!info);

        rcu_read_lock();

        dn = get_dn(muxl, info->dev_info);
        if (dn == NULL) {
                pr_debug("Send data on unknown phy ID = %d (0x%x)\n",
                        info->dev_info->id, info->dev_info->id);
                rcu_read_unlock();
                cfpkt_destroy(pkt);
                return -ENOTCONN;
        }

        info->hdr_len += 1;
        linkid = info->channel_id;
        cfpkt_add_head(pkt, &linkid, 1);

        /* We can't hold rcu_lock during receive, so take a ref count instead */
        cffrml_hold(dn);

        rcu_read_unlock();

        err = dn->transmit(dn, pkt);

        cffrml_put(dn);
        return err;
}

static void cfmuxl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
                           int phyid)
{
        struct cfmuxl *muxl = container_obj(layr);
        struct cflayer *layer;

        rcu_read_lock();
        list_for_each_entry_rcu(layer, &muxl->srvl_list, node) {

                if (cfsrvl_phyid_match(layer, phyid) && layer->ctrlcmd) {

                        if ((ctrl == _CAIF_CTRLCMD_PHYIF_DOWN_IND ||
                                ctrl == CAIF_CTRLCMD_REMOTE_SHUTDOWN_IND) &&
                                        layer->id != 0)
                                cfmuxl_remove_uplayer(layr, layer->id);

                        /* NOTE: ctrlcmd is not allowed to block */
                        layer->ctrlcmd(layer, ctrl, phyid);
                }
        }
        rcu_read_unlock();
}