f_subset.c

Go to the documentation of this file.

/*
 * f_subset.c -- "CDC Subset" Ethernet link function driver
 *
 * Copyright (C) 2003-2005,2008 David Brownell
 * Copyright (C) 2008 Nokia Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

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

#include "u_ether.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 = NULL /* DYNAMIC */,
    {  } /* 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->driver_data) {
        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 IS_ERR(net) ? PTR_ERR(net) : 0;
}

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);
    int         status;
    struct usb_ep       *ep;

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

    status = -ENODEV;

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

    ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_out_desc);
    if (!ep)
        goto fail;
    geth->port.out_ep = ep;
    ep->driver_data = cdev; /* claim */

    /* copy descriptors, and track endpoint copies */
    f->descriptors = usb_copy_descriptors(fs_eth_function);
    if (!f->descriptors)
        goto fail;

    /* support all relevant hardware speeds... we expect that when
     * hardware is dual speed, all bulk-capable endpoints work at
     * both speeds
     */
    if (gadget_is_dualspeed(c->cdev->gadget)) {
        hs_subset_in_desc.bEndpointAddress =
                fs_subset_in_desc.bEndpointAddress;
        hs_subset_out_desc.bEndpointAddress =
                fs_subset_out_desc.bEndpointAddress;

        /* copy descriptors, and track endpoint copies */
        f->hs_descriptors = usb_copy_descriptors(hs_eth_function);
        if (!f->hs_descriptors)
            goto fail;
    }

    if (gadget_is_superspeed(c->cdev->gadget)) {
        ss_subset_in_desc.bEndpointAddress =
                fs_subset_in_desc.bEndpointAddress;
        ss_subset_out_desc.bEndpointAddress =
                fs_subset_out_desc.bEndpointAddress;

        /* copy descriptors, and track endpoint copies */
        f->ss_descriptors = usb_copy_descriptors(ss_eth_function);
        if (!f->ss_descriptors)
            goto fail;
    }

    /* 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().
     */

    DBG(cdev, "CDC Subset: %s speed IN/%s OUT/%s\n",
            gadget_is_superspeed(c->cdev->gadget) ? "super" :
            gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
            geth->port.in_ep->name, geth->port.out_ep->name);
    return 0;

fail:
    if (f->descriptors)
        usb_free_descriptors(f->descriptors);
    if (f->hs_descriptors)
        usb_free_descriptors(f->hs_descriptors);

    /* we might as well release our claims on endpoints */
    if (geth->port.out_ep->desc)
        geth->port.out_ep->driver_data = NULL;
    if (geth->port.in_ep->desc)
        geth->port.in_ep->driver_data = NULL;

    ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);

    return status;
}

static void
geth_unbind(struct usb_configuration *c, struct usb_function *f)
{
    if (gadget_is_superspeed(c->cdev->gadget))
        usb_free_descriptors(f->ss_descriptors);
    if (gadget_is_dualspeed(c->cdev->gadget))
        usb_free_descriptors(f->hs_descriptors);
    usb_free_descriptors(f->descriptors);
    geth_string_defs[1].s = NULL;
    kfree(func_to_geth(f));
}

int geth_bind_config(struct usb_configuration *c, u8 ethaddr[ETH_ALEN])
{
    struct f_gether *geth;
    int     status;

    if (!ethaddr)
        return -EINVAL;

    /* maybe allocate device-global string IDs */
    if (geth_string_defs[0].id == 0) {

        /* interface label */
        status = usb_string_id(c->cdev);
        if (status < 0)
            return status;
        geth_string_defs[0].id = status;
        subset_data_intf.iInterface = status;

        /* MAC address */
        status = usb_string_id(c->cdev);
        if (status < 0)
            return status;
        geth_string_defs[1].id = status;
        ether_desc.iMACAddress = status;
    }

    /* allocate and initialize one new instance */
    geth = kzalloc(sizeof *geth, GFP_KERNEL);
    if (!geth)
        return -ENOMEM;

    /* export host's Ethernet address in CDC format */
    snprintf(geth->ethaddr, sizeof geth->ethaddr, "%pm", ethaddr);
    geth_string_defs[1].s = geth->ethaddr;

    geth->port.cdc_filter = DEFAULT_FILTER;

    geth->port.func.name = "cdc_subset";
    geth->port.func.strings = geth_strings;
    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;

    status = usb_add_function(c, &geth->port.func);
    if (status) {
        geth_string_defs[1].s = NULL;
        kfree(geth);
    }
    return status;
}