f_acm.c

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/*
 * f_acm.c -- USB CDC serial (ACM) function driver
 *
 * Copyright (C) 2003 Al Borchers ([email protected])
 * Copyright (C) 2008 by David Brownell
 * Copyright (C) 2008 by Nokia Corporation
 * Copyright (C) 2009 by Samsung Electronics
 * Author: Michal Nazarewicz ([email protected])
 *
 * This software is distributed under the terms of the GNU General
 * Public License ("GPL") as published by the Free Software Foundation,
 * either version 2 of that License or (at your option) any later version.
 */

/* #define VERBOSE_DEBUG */

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

#include "u_serial.h"
#include "gadget_chips.h"


/*
 * This CDC ACM function support just wraps control functions and
 * notifications around the generic serial-over-usb code.
 *
 * Because CDC ACM is standardized by the USB-IF, many host operating
 * systems have drivers for it.  Accordingly, ACM is the preferred
 * interop solution for serial-port type connections.  The control
 * models are often not necessary, and in any case don't do much in
 * this bare-bones implementation.
 *
 * Note that even MS-Windows has some support for ACM.  However, that
 * support is somewhat broken because when you use ACM in a composite
 * device, having multiple interfaces confuses the poor OS.  It doesn't
 * seem to understand CDC Union descriptors.  The new "association"
 * descriptors (roughly equivalent to CDC Unions) may sometimes help.
 */

struct f_acm {
    struct gserial          port;
    u8              ctrl_id, data_id;
    u8              port_num;

    u8              pending;

    /* lock is mostly for pending and notify_req ... they get accessed
     * by callbacks both from tty (open/close/break) under its spinlock,
     * and notify_req.complete() which can't use that lock.
     */
    spinlock_t          lock;

    struct usb_ep           *notify;
    struct usb_request      *notify_req;

    struct usb_cdc_line_coding  port_line_coding;   /* 8-N-1 etc */

    /* SetControlLineState request -- CDC 1.1 section 6.2.14 (INPUT) */
    u16             port_handshake_bits;
#define ACM_CTRL_RTS    (1 << 1)    /* unused with full duplex */
#define ACM_CTRL_DTR    (1 << 0)    /* host is ready for data r/w */

    /* SerialState notification -- CDC 1.1 section 6.3.5 (OUTPUT) */
    u16             serial_state;
#define ACM_CTRL_OVERRUN    (1 << 6)
#define ACM_CTRL_PARITY     (1 << 5)
#define ACM_CTRL_FRAMING    (1 << 4)
#define ACM_CTRL_RI     (1 << 3)
#define ACM_CTRL_BRK        (1 << 2)
#define ACM_CTRL_DSR        (1 << 1)
#define ACM_CTRL_DCD        (1 << 0)
};

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

static inline struct f_acm *port_to_acm(struct gserial *p)
{
    return container_of(p, struct f_acm, port);
}

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

/* notification endpoint uses smallish and infrequent fixed-size messages */

#define GS_LOG2_NOTIFY_INTERVAL     5   /* 1 << 5 == 32 msec */
#define GS_NOTIFY_MAXPACKET     10  /* notification + 2 bytes */

/* interface and class descriptors: */

static struct usb_interface_assoc_descriptor
acm_iad_descriptor = {
    .bLength =      sizeof acm_iad_descriptor,
    .bDescriptorType =  USB_DT_INTERFACE_ASSOCIATION,

    /* .bFirstInterface =   DYNAMIC, */
    .bInterfaceCount =  2,  // control + data
    .bFunctionClass =   USB_CLASS_COMM,
    .bFunctionSubClass =    USB_CDC_SUBCLASS_ACM,
    .bFunctionProtocol =    USB_CDC_ACM_PROTO_AT_V25TER,
    /* .iFunction =     DYNAMIC */
};


static struct usb_interface_descriptor acm_control_interface_desc = {
    .bLength =      USB_DT_INTERFACE_SIZE,
    .bDescriptorType =  USB_DT_INTERFACE,
    /* .bInterfaceNumber = DYNAMIC */
    .bNumEndpoints =    1,
    .bInterfaceClass =  USB_CLASS_COMM,
    .bInterfaceSubClass =   USB_CDC_SUBCLASS_ACM,
    .bInterfaceProtocol =   USB_CDC_ACM_PROTO_AT_V25TER,
    /* .iInterface = DYNAMIC */
};

static struct usb_interface_descriptor acm_data_interface_desc = {
    .bLength =      USB_DT_INTERFACE_SIZE,
    .bDescriptorType =  USB_DT_INTERFACE,
    /* .bInterfaceNumber = DYNAMIC */
    .bNumEndpoints =    2,
    .bInterfaceClass =  USB_CLASS_CDC_DATA,
    .bInterfaceSubClass =   0,
    .bInterfaceProtocol =   0,
    /* .iInterface = DYNAMIC */
};

static struct usb_cdc_header_desc acm_header_desc = {
    .bLength =      sizeof(acm_header_desc),
    .bDescriptorType =  USB_DT_CS_INTERFACE,
    .bDescriptorSubType =   USB_CDC_HEADER_TYPE,
    .bcdCDC =       cpu_to_le16(0x0110),
};

static struct usb_cdc_call_mgmt_descriptor
acm_call_mgmt_descriptor = {
    .bLength =      sizeof(acm_call_mgmt_descriptor),
    .bDescriptorType =  USB_DT_CS_INTERFACE,
    .bDescriptorSubType =   USB_CDC_CALL_MANAGEMENT_TYPE,
    .bmCapabilities =   0,
    /* .bDataInterface = DYNAMIC */
};

static struct usb_cdc_acm_descriptor acm_descriptor = {
    .bLength =      sizeof(acm_descriptor),
    .bDescriptorType =  USB_DT_CS_INTERFACE,
    .bDescriptorSubType =   USB_CDC_ACM_TYPE,
    .bmCapabilities =   USB_CDC_CAP_LINE,
};

static struct usb_cdc_union_desc acm_union_desc = {
    .bLength =      sizeof(acm_union_desc),
    .bDescriptorType =  USB_DT_CS_INTERFACE,
    .bDescriptorSubType =   USB_CDC_UNION_TYPE,
    /* .bMasterInterface0 = DYNAMIC */
    /* .bSlaveInterface0 =  DYNAMIC */
};

/* full speed support: */

static struct usb_endpoint_descriptor acm_fs_notify_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,
    .bEndpointAddress = USB_DIR_IN,
    .bmAttributes =     USB_ENDPOINT_XFER_INT,
    .wMaxPacketSize =   cpu_to_le16(GS_NOTIFY_MAXPACKET),
    .bInterval =        1 << GS_LOG2_NOTIFY_INTERVAL,
};

static struct usb_endpoint_descriptor acm_fs_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 acm_fs_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 *acm_fs_function[] = {
    (struct usb_descriptor_header *) &acm_iad_descriptor,
    (struct usb_descriptor_header *) &acm_control_interface_desc,
    (struct usb_descriptor_header *) &acm_header_desc,
    (struct usb_descriptor_header *) &acm_call_mgmt_descriptor,
    (struct usb_descriptor_header *) &acm_descriptor,
    (struct usb_descriptor_header *) &acm_union_desc,
    (struct usb_descriptor_header *) &acm_fs_notify_desc,
    (struct usb_descriptor_header *) &acm_data_interface_desc,
    (struct usb_descriptor_header *) &acm_fs_in_desc,
    (struct usb_descriptor_header *) &acm_fs_out_desc,
    NULL,
};

/* high speed support: */

static struct usb_endpoint_descriptor acm_hs_notify_desc = {
    .bLength =      USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =  USB_DT_ENDPOINT,
    .bEndpointAddress = USB_DIR_IN,
    .bmAttributes =     USB_ENDPOINT_XFER_INT,
    .wMaxPacketSize =   cpu_to_le16(GS_NOTIFY_MAXPACKET),
    .bInterval =        GS_LOG2_NOTIFY_INTERVAL+4,
};

static struct usb_endpoint_descriptor acm_hs_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 acm_hs_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 *acm_hs_function[] = {
    (struct usb_descriptor_header *) &acm_iad_descriptor,
    (struct usb_descriptor_header *) &acm_control_interface_desc,
    (struct usb_descriptor_header *) &acm_header_desc,
    (struct usb_descriptor_header *) &acm_call_mgmt_descriptor,
    (struct usb_descriptor_header *) &acm_descriptor,
    (struct usb_descriptor_header *) &acm_union_desc,
    (struct usb_descriptor_header *) &acm_hs_notify_desc,
    (struct usb_descriptor_header *) &acm_data_interface_desc,
    (struct usb_descriptor_header *) &acm_hs_in_desc,
    (struct usb_descriptor_header *) &acm_hs_out_desc,
    NULL,
};

static struct usb_endpoint_descriptor acm_ss_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 acm_ss_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 acm_ss_bulk_comp_desc = {
    .bLength =              sizeof acm_ss_bulk_comp_desc,
    .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
};

static struct usb_descriptor_header *acm_ss_function[] = {
    (struct usb_descriptor_header *) &acm_iad_descriptor,
    (struct usb_descriptor_header *) &acm_control_interface_desc,
    (struct usb_descriptor_header *) &acm_header_desc,
    (struct usb_descriptor_header *) &acm_call_mgmt_descriptor,
    (struct usb_descriptor_header *) &acm_descriptor,
    (struct usb_descriptor_header *) &acm_union_desc,
    (struct usb_descriptor_header *) &acm_hs_notify_desc,
    (struct usb_descriptor_header *) &acm_ss_bulk_comp_desc,
    (struct usb_descriptor_header *) &acm_data_interface_desc,
    (struct usb_descriptor_header *) &acm_ss_in_desc,
    (struct usb_descriptor_header *) &acm_ss_bulk_comp_desc,
    (struct usb_descriptor_header *) &acm_ss_out_desc,
    (struct usb_descriptor_header *) &acm_ss_bulk_comp_desc,
    NULL,
};

/* string descriptors: */

#define ACM_CTRL_IDX    0
#define ACM_DATA_IDX    1
#define ACM_IAD_IDX 2

/* static strings, in UTF-8 */
static struct usb_string acm_string_defs[] = {
    [ACM_CTRL_IDX].s = "CDC Abstract Control Model (ACM)",
    [ACM_DATA_IDX].s = "CDC ACM Data",
    [ACM_IAD_IDX ].s = "CDC Serial",
    {  /* ZEROES END LIST */ },
};

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

static struct usb_gadget_strings *acm_strings[] = {
    &acm_string_table,
    NULL,
};

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

/* ACM control ... data handling is delegated to tty library code.
 * The main task of this function is to activate and deactivate
 * that code based on device state; track parameters like line
 * speed, handshake state, and so on; and issue notifications.
 */

static void acm_complete_set_line_coding(struct usb_ep *ep,
        struct usb_request *req)
{
    struct f_acm    *acm = ep->driver_data;
    struct usb_composite_dev *cdev = acm->port.func.config->cdev;

    if (req->status != 0) {
        DBG(cdev, "acm ttyGS%d completion, err %d\n",
                acm->port_num, req->status);
        return;
    }

    /* normal completion */
    if (req->actual != sizeof(acm->port_line_coding)) {
        DBG(cdev, "acm ttyGS%d short resp, len %d\n",
                acm->port_num, req->actual);
        usb_ep_set_halt(ep);
    } else {
        struct usb_cdc_line_coding  *value = req->buf;

        /* REVISIT:  we currently just remember this data.
         * If we change that, (a) validate it first, then
         * (b) update whatever hardware needs updating,
         * (c) worry about locking.  This is information on
         * the order of 9600-8-N-1 ... most of which means
         * nothing unless we control a real RS232 line.
         */
        acm->port_line_coding = *value;
    }
}

static int acm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
{
    struct f_acm        *acm = func_to_acm(f);
    struct usb_composite_dev *cdev = f->config->cdev;
    struct usb_request  *req = cdev->req;
    int         value = -EOPNOTSUPP;
    u16         w_index = le16_to_cpu(ctrl->wIndex);
    u16         w_value = le16_to_cpu(ctrl->wValue);
    u16         w_length = le16_to_cpu(ctrl->wLength);

    /* composite driver infrastructure handles everything except
     * CDC class messages; interface activation uses set_alt().
     *
     * Note CDC spec table 4 lists the ACM request profile.  It requires
     * encapsulated command support ... we don't handle any, and respond
     * to them by stalling.  Options include get/set/clear comm features
     * (not that useful) and SEND_BREAK.
     */
    switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {

    /* SET_LINE_CODING ... just read and save what the host sends */
    case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
            | USB_CDC_REQ_SET_LINE_CODING:
        if (w_length != sizeof(struct usb_cdc_line_coding)
                || w_index != acm->ctrl_id)
            goto invalid;

        value = w_length;
        cdev->gadget->ep0->driver_data = acm;
        req->complete = acm_complete_set_line_coding;
        break;

    /* GET_LINE_CODING ... return what host sent, or initial value */
    case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
            | USB_CDC_REQ_GET_LINE_CODING:
        if (w_index != acm->ctrl_id)
            goto invalid;

        value = min_t(unsigned, w_length,
                sizeof(struct usb_cdc_line_coding));
        memcpy(req->buf, &acm->port_line_coding, value);
        break;

    /* SET_CONTROL_LINE_STATE ... save what the host sent */
    case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8)
            | USB_CDC_REQ_SET_CONTROL_LINE_STATE:
        if (w_index != acm->ctrl_id)
            goto invalid;

        value = 0;

        /* FIXME we should not allow data to flow until the
         * host sets the ACM_CTRL_DTR bit; and when it clears
         * that bit, we should return to that no-flow state.
         */
        acm->port_handshake_bits = w_value;
        break;

    default:
invalid:
        VDBG(cdev, "invalid control req%02x.%02x v%04x i%04x l%d\n",
            ctrl->bRequestType, ctrl->bRequest,
            w_value, w_index, w_length);
    }

    /* respond with data transfer or status phase? */
    if (value >= 0) {
        DBG(cdev, "acm ttyGS%d req%02x.%02x v%04x i%04x l%d\n",
            acm->port_num, ctrl->bRequestType, ctrl->bRequest,
            w_value, w_index, w_length);
        req->zero = 0;
        req->length = value;
        value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
        if (value < 0)
            ERROR(cdev, "acm response on ttyGS%d, err %d\n",
                    acm->port_num, value);
    }

    /* device either stalls (value < 0) or reports success */
    return value;
}

static int acm_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
    struct f_acm        *acm = func_to_acm(f);
    struct usb_composite_dev *cdev = f->config->cdev;

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

    if (intf == acm->ctrl_id) {
        if (acm->notify->driver_data) {
            VDBG(cdev, "reset acm control interface %d\n", intf);
            usb_ep_disable(acm->notify);
        } else {
            VDBG(cdev, "init acm ctrl interface %d\n", intf);
            if (config_ep_by_speed(cdev->gadget, f, acm->notify))
                return -EINVAL;
        }
        usb_ep_enable(acm->notify);
        acm->notify->driver_data = acm;

    } else if (intf == acm->data_id) {
        if (acm->port.in->driver_data) {
            DBG(cdev, "reset acm ttyGS%d\n", acm->port_num);
            gserial_disconnect(&acm->port);
        }
        if (!acm->port.in->desc || !acm->port.out->desc) {
            DBG(cdev, "activate acm ttyGS%d\n", acm->port_num);
            if (config_ep_by_speed(cdev->gadget, f,
                           acm->port.in) ||
                config_ep_by_speed(cdev->gadget, f,
                           acm->port.out)) {
                acm->port.in->desc = NULL;
                acm->port.out->desc = NULL;
                return -EINVAL;
            }
        }
        gserial_connect(&acm->port, acm->port_num);

    } else
        return -EINVAL;

    return 0;
}

static void acm_disable(struct usb_function *f)
{
    struct f_acm    *acm = func_to_acm(f);
    struct usb_composite_dev *cdev = f->config->cdev;

    DBG(cdev, "acm ttyGS%d deactivated\n", acm->port_num);
    gserial_disconnect(&acm->port);
    usb_ep_disable(acm->notify);
    acm->notify->driver_data = NULL;
}

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

static int acm_cdc_notify(struct f_acm *acm, u8 type, u16 value,
        void *data, unsigned length)
{
    struct usb_ep           *ep = acm->notify;
    struct usb_request      *req;
    struct usb_cdc_notification *notify;
    const unsigned          len = sizeof(*notify) + length;
    void                *buf;
    int             status;

    req = acm->notify_req;
    acm->notify_req = NULL;
    acm->pending = false;

    req->length = len;
    notify = req->buf;
    buf = notify + 1;

    notify->bmRequestType = USB_DIR_IN | USB_TYPE_CLASS
            | USB_RECIP_INTERFACE;
    notify->bNotificationType = type;
    notify->wValue = cpu_to_le16(value);
    notify->wIndex = cpu_to_le16(acm->ctrl_id);
    notify->wLength = cpu_to_le16(length);
    memcpy(buf, data, length);

    /* ep_queue() can complete immediately if it fills the fifo... */
    spin_unlock(&acm->lock);
    status = usb_ep_queue(ep, req, GFP_ATOMIC);
    spin_lock(&acm->lock);

    if (status < 0) {
        ERROR(acm->port.func.config->cdev,
                "acm ttyGS%d can't notify serial state, %d\n",
                acm->port_num, status);
        acm->notify_req = req;
    }

    return status;
}

static int acm_notify_serial_state(struct f_acm *acm)
{
    struct usb_composite_dev *cdev = acm->port.func.config->cdev;
    int         status;

    spin_lock(&acm->lock);
    if (acm->notify_req) {
        DBG(cdev, "acm ttyGS%d serial state %04x\n",
                acm->port_num, acm->serial_state);
        status = acm_cdc_notify(acm, USB_CDC_NOTIFY_SERIAL_STATE,
                0, &acm->serial_state, sizeof(acm->serial_state));
    } else {
        acm->pending = true;
        status = 0;
    }
    spin_unlock(&acm->lock);
    return status;
}

static void acm_cdc_notify_complete(struct usb_ep *ep, struct usb_request *req)
{
    struct f_acm        *acm = req->context;
    u8          doit = false;

    /* on this call path we do NOT hold the port spinlock,
     * which is why ACM needs its own spinlock
     */
    spin_lock(&acm->lock);
    if (req->status != -ESHUTDOWN)
        doit = acm->pending;
    acm->notify_req = req;
    spin_unlock(&acm->lock);

    if (doit)
        acm_notify_serial_state(acm);
}

/* connect == the TTY link is open */

static void acm_connect(struct gserial *port)
{
    struct f_acm        *acm = port_to_acm(port);

    acm->serial_state |= ACM_CTRL_DSR | ACM_CTRL_DCD;
    acm_notify_serial_state(acm);
}

static void acm_disconnect(struct gserial *port)
{
    struct f_acm        *acm = port_to_acm(port);

    acm->serial_state &= ~(ACM_CTRL_DSR | ACM_CTRL_DCD);
    acm_notify_serial_state(acm);
}

static int acm_send_break(struct gserial *port, int duration)
{
    struct f_acm        *acm = port_to_acm(port);
    u16         state;

    state = acm->serial_state;
    state &= ~ACM_CTRL_BRK;
    if (duration)
        state |= ACM_CTRL_BRK;

    acm->serial_state = state;
    return acm_notify_serial_state(acm);
}

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

/* ACM function driver setup/binding */
static int
acm_bind(struct usb_configuration *c, struct usb_function *f)
{
    struct usb_composite_dev *cdev = c->cdev;
    struct f_acm        *acm = func_to_acm(f);
    int         status;
    struct usb_ep       *ep;

    /* allocate instance-specific interface IDs, and patch descriptors */
    status = usb_interface_id(c, f);
    if (status < 0)
        goto fail;
    acm->ctrl_id = status;
    acm_iad_descriptor.bFirstInterface = status;

    acm_control_interface_desc.bInterfaceNumber = status;
    acm_union_desc .bMasterInterface0 = status;

    status = usb_interface_id(c, f);
    if (status < 0)
        goto fail;
    acm->data_id = status;

    acm_data_interface_desc.bInterfaceNumber = status;
    acm_union_desc.bSlaveInterface0 = status;
    acm_call_mgmt_descriptor.bDataInterface = status;

    status = -ENODEV;

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

    ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_out_desc);
    if (!ep)
        goto fail;
    acm->port.out = ep;
    ep->driver_data = cdev; /* claim */

    ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_notify_desc);
    if (!ep)
        goto fail;
    acm->notify = ep;
    ep->driver_data = cdev; /* claim */

    /* allocate notification */
    acm->notify_req = gs_alloc_req(ep,
            sizeof(struct usb_cdc_notification) + 2,
            GFP_KERNEL);
    if (!acm->notify_req)
        goto fail;

    acm->notify_req->complete = acm_cdc_notify_complete;
    acm->notify_req->context = acm;

    /* copy descriptors */
    f->descriptors = usb_copy_descriptors(acm_fs_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)) {
        acm_hs_in_desc.bEndpointAddress =
                acm_fs_in_desc.bEndpointAddress;
        acm_hs_out_desc.bEndpointAddress =
                acm_fs_out_desc.bEndpointAddress;
        acm_hs_notify_desc.bEndpointAddress =
                acm_fs_notify_desc.bEndpointAddress;

        /* copy descriptors */
        f->hs_descriptors = usb_copy_descriptors(acm_hs_function);
    }
    if (gadget_is_superspeed(c->cdev->gadget)) {
        acm_ss_in_desc.bEndpointAddress =
            acm_fs_in_desc.bEndpointAddress;
        acm_ss_out_desc.bEndpointAddress =
            acm_fs_out_desc.bEndpointAddress;

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

    DBG(cdev, "acm ttyGS%d: %s speed IN/%s OUT/%s NOTIFY/%s\n",
            acm->port_num,
            gadget_is_superspeed(c->cdev->gadget) ? "super" :
            gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
            acm->port.in->name, acm->port.out->name,
            acm->notify->name);
    return 0;

fail:
    if (acm->notify_req)
        gs_free_req(acm->notify, acm->notify_req);

    /* we might as well release our claims on endpoints */
    if (acm->notify)
        acm->notify->driver_data = NULL;
    if (acm->port.out)
        acm->port.out->driver_data = NULL;
    if (acm->port.in)
        acm->port.in->driver_data = NULL;

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

    return status;
}

static void
acm_unbind(struct usb_configuration *c, struct usb_function *f)
{
    struct f_acm        *acm = func_to_acm(f);

    if (gadget_is_dualspeed(c->cdev->gadget))
        usb_free_descriptors(f->hs_descriptors);
    if (gadget_is_superspeed(c->cdev->gadget))
        usb_free_descriptors(f->ss_descriptors);
    usb_free_descriptors(f->descriptors);
    gs_free_req(acm->notify, acm->notify_req);
    kfree(acm);
}

/* Some controllers can't support CDC ACM ... */
static inline bool can_support_cdc(struct usb_configuration *c)
{
    /* everything else is *probably* fine ... */
    return true;
}

int acm_bind_config(struct usb_configuration *c, u8 port_num)
{
    struct f_acm    *acm;
    int     status;

    if (!can_support_cdc(c))
        return -EINVAL;

    /* REVISIT might want instance-specific strings to help
     * distinguish instances ...
     */

    /* maybe allocate device-global string IDs, and patch descriptors */
    if (acm_string_defs[ACM_CTRL_IDX].id == 0) {
        status = usb_string_id(c->cdev);
        if (status < 0)
            return status;
        acm_string_defs[ACM_CTRL_IDX].id = status;

        acm_control_interface_desc.iInterface = status;

        status = usb_string_id(c->cdev);
        if (status < 0)
            return status;
        acm_string_defs[ACM_DATA_IDX].id = status;

        acm_data_interface_desc.iInterface = status;

        status = usb_string_id(c->cdev);
        if (status < 0)
            return status;
        acm_string_defs[ACM_IAD_IDX].id = status;

        acm_iad_descriptor.iFunction = status;
    }

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

    spin_lock_init(&acm->lock);

    acm->port_num = port_num;

    acm->port.connect = acm_connect;
    acm->port.disconnect = acm_disconnect;
    acm->port.send_break = acm_send_break;

    acm->port.func.name = "acm";
    acm->port.func.strings = acm_strings;
    /* descriptors are per-instance copies */
    acm->port.func.bind = acm_bind;
    acm->port.func.unbind = acm_unbind;
    acm->port.func.set_alt = acm_set_alt;
    acm->port.func.setup = acm_setup;
    acm->port.func.disable = acm_disable;

    status = usb_add_function(c, &acm->port.func);
    if (status)
        kfree(acm);
    return status;
}