// SPDX-License-Identifier: GPL-2.0+
/*
 * f_subset.c -- "CDC Subset" Ethernet link function driver
 *
 * Copyright (C) 2003-2005,2008 David Brownell
 * Copyright (C) 2008 Nokia Corporation
 */

#include <linux/cleanup.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/etherdevice.h>

#include "u_ether.h"
#include "u_ether_configfs.h"
#include "u_gether.h"

/*
 * This function packages a simple "CDC Subset" Ethernet port with no real
 * control mechanisms; just raw data transfer over two bulk endpoints.
 * The data transfer model is exactly that of CDC Ethernet, which is
 * why we call it the "CDC Subset".
 *
 * Because it's not standardized, this has some interoperability issues.
 * They mostly relate to driver binding, since the data transfer model is
 * so simple (CDC Ethernet).  The original versions of this protocol used
 * specific product/vendor IDs:  byteswapped IDs for Digital Equipment's
 * SA-1100 "Itsy" board, which could run Linux 2.4 kernels and supported
 * daughtercards with USB peripheral connectors.  (It was used more often
 * with other boards, using the Itsy identifiers.)  Linux hosts recognized
 * this with CONFIG_USB_ARMLINUX; these devices have only one configuration
 * and one interface.
 *
 * At some point, MCCI defined a (nonconformant) CDC MDLM variant called
 * "SAFE", which happens to have a mode which is identical to the "CDC
 * Subset" in terms of data transfer and lack of control model.  This was
 * adopted by later Sharp Zaurus models, and by some other software which
 * Linux hosts recognize with CONFIG_USB_NET_ZAURUS.
 *
 * Because Microsoft's RNDIS drivers are far from robust, we added a few
 * descriptors to the CDC Subset code, making this code look like a SAFE
 * implementation.  This lets you use MCCI's host side MS-Windows drivers
 * if you get fed up with RNDIS.  It also makes it easier for composite
 * drivers to work, since they can use class based binding instead of
 * caring about specific product and vendor IDs.
 */

struct f_gether {
        struct gether                   port;

        char                            ethaddr[14];
};

static inline struct f_gether *func_to_geth(struct usb_function *f)
{
        return container_of(f, struct f_gether, port.func);
}

/*-------------------------------------------------------------------------*/

/*
 * "Simple" CDC-subset option is a simple vendor-neutral model that most
 * full speed controllers can handle:  one interface, two bulk endpoints.
 * To assist host side drivers, we fancy it up a bit, and add descriptors so
 * some host side drivers will understand it as a "SAFE" variant.
 *
 * "SAFE" loosely follows CDC WMC MDLM, violating the spec in various ways.
 * Data endpoints live in the control interface, there's no data interface.
 * And it's not used to talk to a cell phone radio.
 */

/* interface descriptor: */

static struct usb_interface_descriptor subset_data_intf = {
        .bLength =              sizeof subset_data_intf,
        .bDescriptorType =      USB_DT_INTERFACE,

        /* .bInterfaceNumber = DYNAMIC */
        .bAlternateSetting =    0,
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_COMM,
        .bInterfaceSubClass =   USB_CDC_SUBCLASS_MDLM,
        .bInterfaceProtocol =   0,
        /* .iInterface = DYNAMIC */
};

static struct usb_cdc_header_desc mdlm_header_desc = {
        .bLength =              sizeof mdlm_header_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_HEADER_TYPE,

        .bcdCDC =               cpu_to_le16(0x0110),
};

static struct usb_cdc_mdlm_desc mdlm_desc = {
        .bLength =              sizeof mdlm_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_MDLM_TYPE,

        .bcdVersion =           cpu_to_le16(0x0100),
        .bGUID = {
                0x5d, 0x34, 0xcf, 0x66, 0x11, 0x18, 0x11, 0xd6,
                0xa2, 0x1a, 0x00, 0x01, 0x02, 0xca, 0x9a, 0x7f,
        },
};

/* since "usb_cdc_mdlm_detail_desc" is a variable length structure, we
 * can't really use its struct.  All we do here is say that we're using
 * the submode of "SAFE" which directly matches the CDC Subset.
 */
static u8 mdlm_detail_desc[] = {
        6,
        USB_DT_CS_INTERFACE,
        USB_CDC_MDLM_DETAIL_TYPE,

        0,      /* "SAFE" */
        0,      /* network control capabilities (none) */
        0,      /* network data capabilities ("raw" encapsulation) */
};

static struct usb_cdc_ether_desc ether_desc = {
        .bLength =              sizeof ether_desc,
        .bDescriptorType =      USB_DT_CS_INTERFACE,
        .bDescriptorSubType =   USB_CDC_ETHERNET_TYPE,

        /* this descriptor actually adds value, surprise! */
        /* .iMACAddress = DYNAMIC */
        .bmEthernetStatistics = cpu_to_le32(0), /* no statistics */
        .wMaxSegmentSize =      cpu_to_le16(ETH_FRAME_LEN),
        .wNumberMCFilters =     cpu_to_le16(0),
        .bNumberPowerFilters =  0,
};

/* full speed support: */

static struct usb_endpoint_descriptor fs_subset_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_endpoint_descriptor fs_subset_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
};

static struct usb_descriptor_header *fs_eth_function[] = {
        (struct usb_descriptor_header *) &subset_data_intf,
        (struct usb_descriptor_header *) &mdlm_header_desc,
        (struct usb_descriptor_header *) &mdlm_desc,
        (struct usb_descriptor_header *) &mdlm_detail_desc,
        (struct usb_descriptor_header *) &ether_desc,
        (struct usb_descriptor_header *) &fs_subset_in_desc,
        (struct usb_descriptor_header *) &fs_subset_out_desc,
        NULL,
};

/* high speed support: */

static struct usb_endpoint_descriptor hs_subset_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(512),
};

static struct usb_endpoint_descriptor hs_subset_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(512),
};

static struct usb_descriptor_header *hs_eth_function[] = {
        (struct usb_descriptor_header *) &subset_data_intf,
        (struct usb_descriptor_header *) &mdlm_header_desc,
        (struct usb_descriptor_header *) &mdlm_desc,
        (struct usb_descriptor_header *) &mdlm_detail_desc,
        (struct usb_descriptor_header *) &ether_desc,
        (struct usb_descriptor_header *) &hs_subset_in_desc,
        (struct usb_descriptor_header *) &hs_subset_out_desc,
        NULL,
};

/* super speed support: */

static struct usb_endpoint_descriptor ss_subset_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(1024),
};

static struct usb_endpoint_descriptor ss_subset_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,

        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor ss_subset_bulk_comp_desc = {
        .bLength =              sizeof ss_subset_bulk_comp_desc,
        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,

        /* the following 2 values can be tweaked if necessary */
        /* .bMaxBurst =         0, */
        /* .bmAttributes =      0, */
};

static struct usb_descriptor_header *ss_eth_function[] = {
        (struct usb_descriptor_header *) &subset_data_intf,
        (struct usb_descriptor_header *) &mdlm_header_desc,
        (struct usb_descriptor_header *) &mdlm_desc,
        (struct usb_descriptor_header *) &mdlm_detail_desc,
        (struct usb_descriptor_header *) &ether_desc,
        (struct usb_descriptor_header *) &ss_subset_in_desc,
        (struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
        (struct usb_descriptor_header *) &ss_subset_out_desc,
        (struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
        NULL,
};

/* string descriptors: */

static struct usb_string geth_string_defs[] = {
        [0].s = "CDC Ethernet Subset/SAFE",
        [1].s = "",
        {  } /* end of list */
};

static struct usb_gadget_strings geth_string_table = {
        .language =             0x0409, /* en-us */
        .strings =              geth_string_defs,
};

static struct usb_gadget_strings *geth_strings[] = {
        &geth_string_table,
        NULL,
};

/*-------------------------------------------------------------------------*/

static int geth_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct f_gether         *geth = func_to_geth(f);
        struct usb_composite_dev *cdev = f->config->cdev;
        struct net_device       *net;

        /* we know alt == 0, so this is an activation or a reset */

        if (geth->port.in_ep->enabled) {
                DBG(cdev, "reset cdc subset\n");
                gether_disconnect(&geth->port);
        }

        DBG(cdev, "init + activate cdc subset\n");
        if (config_ep_by_speed(cdev->gadget, f, geth->port.in_ep) ||
            config_ep_by_speed(cdev->gadget, f, geth->port.out_ep)) {
                geth->port.in_ep->desc = NULL;
                geth->port.out_ep->desc = NULL;
                return -EINVAL;
        }

        net = gether_connect(&geth->port);
        return PTR_ERR_OR_ZERO(net);
}

static void geth_disable(struct usb_function *f)
{
        struct f_gether *geth = func_to_geth(f);
        struct usb_composite_dev *cdev = f->config->cdev;

        DBG(cdev, "net deactivated\n");
        gether_disconnect(&geth->port);
}

/*-------------------------------------------------------------------------*/

/* serial function driver setup/binding */

static int
geth_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev *cdev = c->cdev;
        struct f_gether         *geth = func_to_geth(f);
        struct usb_string       *us;
        int                     status;
        struct usb_ep           *ep;

        struct f_gether_opts    *gether_opts;
        struct net_device       *net __free(detach_gadget) = NULL;

        gether_opts = container_of(f->fi, struct f_gether_opts, func_inst);

        scoped_guard(mutex, &gether_opts->lock)
                if (gether_opts->bind_count == 0 && !gether_opts->bound) {
                        if (!device_is_registered(&gether_opts->net->dev)) {
                                gether_set_gadget(gether_opts->net, cdev->gadget);
                                status = gether_register_netdev(gether_opts->net);
                        } else
                                status = gether_attach_gadget(gether_opts->net, cdev->gadget);

                        if (status)
                                return status;
                        net = gether_opts->net;
                }

        us = usb_gstrings_attach(cdev, geth_strings,
                                 ARRAY_SIZE(geth_string_defs));
        if (IS_ERR(us))
                return PTR_ERR(us);

        subset_data_intf.iInterface = us[0].id;
        ether_desc.iMACAddress = us[1].id;

        /* allocate instance-specific interface IDs */
        status = usb_interface_id(c, f);
        if (status < 0)
                return status;
        subset_data_intf.bInterfaceNumber = status;

        /* allocate instance-specific endpoints */
        ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_in_desc);
        if (!ep)
                return -ENODEV;
        geth->port.in_ep = ep;

        ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_out_desc);
        if (!ep)
                return -ENODEV;
        geth->port.out_ep = ep;

        /* support all relevant hardware speeds... we expect that when
         * hardware is dual speed, all bulk-capable endpoints work at
         * both speeds
         */
        hs_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
        hs_subset_out_desc.bEndpointAddress =
                fs_subset_out_desc.bEndpointAddress;

        ss_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
        ss_subset_out_desc.bEndpointAddress =
                fs_subset_out_desc.bEndpointAddress;

        status = usb_assign_descriptors(f, fs_eth_function, hs_eth_function,
                        ss_eth_function, ss_eth_function);
        if (status)
                return status;

        /* NOTE:  all that is done without knowing or caring about
         * the network link ... which is unavailable to this code
         * until we're activated via set_alt().
         */

        gether_opts->bind_count++;
        retain_and_null_ptr(net);

        DBG(cdev, "CDC Subset: IN/%s OUT/%s\n",
                        geth->port.in_ep->name, geth->port.out_ep->name);
        return 0;
}

static inline struct f_gether_opts *to_f_gether_opts(struct config_item *item)
{
        return container_of(to_config_group(item), struct f_gether_opts,
                            func_inst.group);
}

/* f_gether_item_ops */
USB_ETHERNET_CONFIGFS_ITEM(gether);

/* f_gether_opts_dev_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(gether);

/* f_gether_opts_host_addr */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(gether);

/* f_gether_opts_qmult */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(gether);

/* f_gether_opts_ifname */
USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(gether);

static struct configfs_attribute *gether_attrs[] = {
        &gether_opts_attr_dev_addr,
        &gether_opts_attr_host_addr,
        &gether_opts_attr_qmult,
        &gether_opts_attr_ifname,
        NULL,
};

static const struct config_item_type gether_func_type = {
        .ct_item_ops    = &gether_item_ops,
        .ct_attrs       = gether_attrs,
        .ct_owner       = THIS_MODULE,
};

static void geth_free_inst(struct usb_function_instance *f)
{
        struct f_gether_opts *opts;

        opts = container_of(f, struct f_gether_opts, func_inst);
        if (device_is_registered(&opts->net->dev))
                gether_cleanup(netdev_priv(opts->net));
        else
                free_netdev(opts->net);
        kfree(opts);
}

static struct usb_function_instance *geth_alloc_inst(void)
{
        struct f_gether_opts *opts;

        opts = kzalloc_obj(*opts);
        if (!opts)
                return ERR_PTR(-ENOMEM);
        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = geth_free_inst;
        opts->net = gether_setup_default();
        if (IS_ERR(opts->net)) {
                struct net_device *net = opts->net;
                kfree(opts);
                return ERR_CAST(net);
        }

        config_group_init_type_name(&opts->func_inst.group, "",
                                    &gether_func_type);

        return &opts->func_inst;
}

static void geth_free(struct usb_function *f)
{
        struct f_gether *eth;
        struct f_gether_opts *opts;

        opts = container_of(f->fi, struct f_gether_opts, func_inst);

        eth = func_to_geth(f);
        scoped_guard(mutex, &opts->lock)
                opts->refcnt--;
        kfree(eth);
}

static void geth_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct f_gether_opts *opts;

        opts = container_of(f->fi, struct f_gether_opts, func_inst);

        geth_string_defs[0].id = 0;
        usb_free_all_descriptors(f);

        opts->bind_count--;
        if (opts->bind_count == 0 && !opts->bound)
                gether_detach_gadget(opts->net);
}

static struct usb_function *geth_alloc(struct usb_function_instance *fi)
{
        struct f_gether *geth;
        struct f_gether_opts *opts;
        int status;

        /* allocate and initialize one new instance */
        geth = kzalloc_obj(*geth);
        if (!geth)
                return ERR_PTR(-ENOMEM);

        opts = container_of(fi, struct f_gether_opts, func_inst);

        mutex_lock(&opts->lock);
        opts->refcnt++;
        /* export host's Ethernet address in CDC format */
        status = gether_get_host_addr_cdc(opts->net, geth->ethaddr,
                                          sizeof(geth->ethaddr));
        if (status < 12) {
                kfree(geth);
                mutex_unlock(&opts->lock);
                return ERR_PTR(-EINVAL);
        }
        geth_string_defs[1].s = geth->ethaddr;

        geth->port.ioport = netdev_priv(opts->net);
        mutex_unlock(&opts->lock);
        geth->port.cdc_filter = DEFAULT_FILTER;

        geth->port.func.name = "cdc_subset";
        geth->port.func.bind = geth_bind;
        geth->port.func.unbind = geth_unbind;
        geth->port.func.set_alt = geth_set_alt;
        geth->port.func.disable = geth_disable;
        geth->port.func.free_func = geth_free;

        return &geth->port.func;
}

DECLARE_USB_FUNCTION_INIT(geth, geth_alloc_inst, geth_alloc);
MODULE_DESCRIPTION("\"CDC Subset\" Ethernet link function driver");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("David Brownell");