// SPDX-License-Identifier: GPL-2.0-only
/*
 * CAIF USB handler
 * Copyright (C) ST-Ericsson AB 2011
 * Author:      Sjur Brendeland
 */

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

#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/slab.h>
#include <linux/mii.h>
#include <linux/usb.h>
#include <linux/usb/usbnet.h>
#include <linux/etherdevice.h>
#include <net/netns/generic.h>
#include <net/caif/caif_dev.h>
#include <net/caif/caif_layer.h>
#include <net/caif/cfpkt.h>
#include <net/caif/cfcnfg.h>

MODULE_DESCRIPTION("ST-Ericsson CAIF modem protocol USB support");
MODULE_LICENSE("GPL");

#define CFUSB_PAD_DESCR_SZ 1    /* Alignment descriptor length */
#define CFUSB_ALIGNMENT 4       /* Number of bytes to align. */
#define CFUSB_MAX_HEADLEN (CFUSB_PAD_DESCR_SZ + CFUSB_ALIGNMENT-1)
#define STE_USB_VID 0x04cc      /* USB Product ID for ST-Ericsson */
#define STE_USB_PID_CAIF 0x230f /* Product id for CAIF Modems */

struct cfusbl {
        struct cflayer layer;
        u8 tx_eth_hdr[ETH_HLEN];
};

static bool pack_added;

static int cfusbl_receive(struct cflayer *layr, struct cfpkt *pkt)
{
        u8 hpad;

        /* Remove padding. */
        cfpkt_extr_head(pkt, &hpad, 1);
        cfpkt_extr_head(pkt, NULL, hpad);
        return layr->up->receive(layr->up, pkt);
}

static int cfusbl_transmit(struct cflayer *layr, struct cfpkt *pkt)
{
        struct caif_payload_info *info;
        u8 hpad;
        u8 zeros[CFUSB_ALIGNMENT];
        struct sk_buff *skb;
        struct cfusbl *usbl = container_of(layr, struct cfusbl, layer);

        skb = cfpkt_tonative(pkt);

        skb_reset_network_header(skb);
        skb->protocol = htons(ETH_P_IP);

        info = cfpkt_info(pkt);
        hpad = (info->hdr_len + CFUSB_PAD_DESCR_SZ) & (CFUSB_ALIGNMENT - 1);

        if (skb_headroom(skb) < ETH_HLEN + CFUSB_PAD_DESCR_SZ + hpad) {
                pr_warn("Headroom too small\n");
                kfree_skb(skb);
                return -EIO;
        }
        memset(zeros, 0, hpad);

        cfpkt_add_head(pkt, zeros, hpad);
        cfpkt_add_head(pkt, &hpad, 1);
        cfpkt_add_head(pkt, usbl->tx_eth_hdr, sizeof(usbl->tx_eth_hdr));
        return layr->dn->transmit(layr->dn, pkt);
}

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

static struct cflayer *cfusbl_create(int phyid, const u8 ethaddr[ETH_ALEN],
                                      u8 braddr[ETH_ALEN])
{
        struct cfusbl *this = kmalloc_obj(struct cfusbl, GFP_ATOMIC);

        if (!this)
                return NULL;

        caif_assert(offsetof(struct cfusbl, layer) == 0);

        memset(&this->layer, 0, sizeof(this->layer));
        this->layer.receive = cfusbl_receive;
        this->layer.transmit = cfusbl_transmit;
        this->layer.ctrlcmd = cfusbl_ctrlcmd;
        snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "usb%d", phyid);
        this->layer.id = phyid;

        /*
         * Construct TX ethernet header:
         *      0-5     destination address
         *      5-11    source address
         *      12-13   protocol type
         */
        ether_addr_copy(&this->tx_eth_hdr[ETH_ALEN], braddr);
        ether_addr_copy(&this->tx_eth_hdr[ETH_ALEN], ethaddr);
        this->tx_eth_hdr[12] = cpu_to_be16(ETH_P_802_EX1) & 0xff;
        this->tx_eth_hdr[13] = (cpu_to_be16(ETH_P_802_EX1) >> 8) & 0xff;
        pr_debug("caif ethernet TX-header dst:%pM src:%pM type:%02x%02x\n",
                        this->tx_eth_hdr, this->tx_eth_hdr + ETH_ALEN,
                        this->tx_eth_hdr[12], this->tx_eth_hdr[13]);

        return (struct cflayer *) this;
}

static void cfusbl_release(struct cflayer *layer)
{
        kfree(layer);
}

static struct packet_type caif_usb_type __read_mostly = {
        .type = cpu_to_be16(ETH_P_802_EX1),
};

static int cfusbl_device_notify(struct notifier_block *me, unsigned long what,
                                void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);
        struct caif_dev_common common;
        struct cflayer *layer, *link_support;
        struct usbnet *usbnet;
        struct usb_device *usbdev;
        int res;

        if (what == NETDEV_UNREGISTER && dev->reg_state >= NETREG_UNREGISTERED)
                return 0;

        /* Check whether we have a NCM device, and find its VID/PID. */
        if (!(dev->dev.parent && dev->dev.parent->driver &&
              strcmp(dev->dev.parent->driver->name, "cdc_ncm") == 0))
                return 0;

        usbnet = netdev_priv(dev);
        usbdev = usbnet->udev;

        pr_debug("USB CDC NCM device VID:0x%4x PID:0x%4x\n",
                le16_to_cpu(usbdev->descriptor.idVendor),
                le16_to_cpu(usbdev->descriptor.idProduct));

        /* Check for VID/PID that supports CAIF */
        if (!(le16_to_cpu(usbdev->descriptor.idVendor) == STE_USB_VID &&
                le16_to_cpu(usbdev->descriptor.idProduct) == STE_USB_PID_CAIF))
                return 0;

        if (what == NETDEV_UNREGISTER)
                module_put(THIS_MODULE);

        if (what != NETDEV_REGISTER)
                return 0;

        __module_get(THIS_MODULE);

        memset(&common, 0, sizeof(common));
        common.use_frag = false;
        common.use_fcs = false;
        common.use_stx = false;
        common.link_select = CAIF_LINK_HIGH_BANDW;
        common.flowctrl = NULL;

        link_support = cfusbl_create(dev->ifindex, dev->dev_addr,
                                        dev->broadcast);

        if (!link_support)
                return -ENOMEM;

        if (dev->num_tx_queues > 1)
                pr_warn("USB device uses more than one tx queue\n");

        res = caif_enroll_dev(dev, &common, link_support, CFUSB_MAX_HEADLEN,
                        &layer, &caif_usb_type.func);
        if (res)
                goto err;

        if (!pack_added)
                dev_add_pack(&caif_usb_type);
        pack_added = true;

        strscpy(layer->name, dev->name, sizeof(layer->name));

        return 0;
err:
        cfusbl_release(link_support);
        return res;
}

static struct notifier_block caif_device_notifier = {
        .notifier_call = cfusbl_device_notify,
        .priority = 0,
};

static int __init cfusbl_init(void)
{
        return register_netdevice_notifier(&caif_device_notifier);
}

static void __exit cfusbl_exit(void)
{
        unregister_netdevice_notifier(&caif_device_notifier);
        dev_remove_pack(&caif_usb_type);
}

module_init(cfusbl_init);
module_exit(cfusbl_exit);