/*
 * f_acm.c -- USB CDC serial (ACM) function driver
 *
 * Copyright (C) 2003 Al Borchers (alborchers@steinerpoint.com)
 * Copyright (C) 2008 by David Brownell
 * Copyright (C) 2008 by Nokia Corporation
 *
 * 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/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 acm_ep_descs {
        struct usb_endpoint_descriptor  *in;
        struct usb_endpoint_descriptor  *out;
        struct usb_endpoint_descriptor  *notify;
};

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 acm_ep_descs             fs;
        struct acm_ep_descs             hs;

        struct usb_ep                   *notify;
        struct usb_endpoint_descriptor  *notify_desc;
        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_descriptor acm_control_interface_desc __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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[] __initdata = {
        (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 __initdata = {
        .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 __initdata = {
        .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 __initdata = {
        .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[] __initdata = {
        (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,
};

/* string descriptors: */

#define ACM_CTRL_IDX    0
#define ACM_DATA_IDX    1

/* 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",
        {  /* 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);
                        acm->notify_desc = ep_choose(cdev->gadget,
                                        acm->hs.notify,
                                        acm->fs.notify);
                }
                usb_ep_enable(acm->notify, acm->notify_desc);
                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);
                } else {
                        DBG(cdev, "activate acm ttyGS%d\n", acm->port_num);
                        acm->port.in_desc = ep_choose(cdev->gadget,
                                        acm->hs.in, acm->fs.in);
                        acm->port.out_desc = ep_choose(cdev->gadget,
                                        acm->hs.out, acm->fs.out);
                }
                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;
}

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

/**
 * acm_cdc_notify - issue CDC notification to host
 * @acm: wraps host to be notified
 * @type: notification type
 * @value: Refer to cdc specs, wValue field.
 * @data: data to be sent
 * @length: size of data
 * Context: irqs blocked, acm->lock held, acm_notify_req non-null
 *
 * Returns zero on sucess or a negative errno.
 *
 * See section 6.3.5 of the CDC 1.1 specification for information
 * about the only notification we issue:  SerialState change.
 */
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 __init
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_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, and track endpoint copies */
        f->descriptors = usb_copy_descriptors(acm_fs_function);
        if (!f->descriptors)
                goto fail;

        acm->fs.in = usb_find_endpoint(acm_fs_function,
                        f->descriptors, &acm_fs_in_desc);
        acm->fs.out = usb_find_endpoint(acm_fs_function,
                        f->descriptors, &acm_fs_out_desc);
        acm->fs.notify = usb_find_endpoint(acm_fs_function,
                        f->descriptors, &acm_fs_notify_desc);

        /* 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, and track endpoint copies */
                f->hs_descriptors = usb_copy_descriptors(acm_hs_function);

                acm->hs.in = usb_find_endpoint(acm_hs_function,
                                f->hs_descriptors, &acm_hs_in_desc);
                acm->hs.out = usb_find_endpoint(acm_hs_function,
                                f->hs_descriptors, &acm_hs_out_desc);
                acm->hs.notify = usb_find_endpoint(acm_hs_function,
                                f->hs_descriptors, &acm_hs_notify_desc);
        }

        DBG(cdev, "acm ttyGS%d: %s speed IN/%s OUT/%s NOTIFY/%s\n",
                        acm->port_num,
                        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);
        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)
{
        /* SH3 doesn't support multiple interfaces */
        if (gadget_is_sh(c->cdev->gadget))
                return false;

        /* sa1100 doesn't have a third interrupt endpoint */
        if (gadget_is_sa1100(c->cdev->gadget))
                return false;

        /* everything else is *probably* fine ... */
        return true;
}

/**
 * acm_bind_config - add a CDC ACM function to a configuration
 * @c: the configuration to support the CDC ACM instance
 * @port_num: /dev/ttyGS* port this interface will use
 * Context: single threaded during gadget setup
 *
 * Returns zero on success, else negative errno.
 *
 * Caller must have called @gserial_setup() with enough ports to
 * handle all the ones it binds.  Caller is also responsible
 * for calling @gserial_cleanup() before module unload.
 */
int __init 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;
        }

        /* 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;
}