// SPDX-License-Identifier: GPL-2.0+
/*
 * f_hid.c -- USB HID function driver
 *
 * Copyright (C) 2010 Fabien Chouteau <fabien.chouteau@barco.com>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/hid.h>
#include <linux/idr.h>
#include <linux/cdev.h>
#include <linux/mutex.h>
#include <linux/poll.h>
#include <linux/uaccess.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/usb/g_hid.h>

#include "u_f.h"
#include "u_hid.h"

#define HIDG_MINORS     4

static int major, minors;
static struct class *hidg_class;
static DEFINE_IDA(hidg_ida);
static DEFINE_MUTEX(hidg_ida_lock); /* protects access to hidg_ida */

/*-------------------------------------------------------------------------*/
/*                            HID gadget struct                            */

struct f_hidg_req_list {
        struct usb_request      *req;
        unsigned int            pos;
        struct list_head        list;
};

struct f_hidg {
        /* configuration */
        unsigned char                   bInterfaceSubClass;
        unsigned char                   bInterfaceProtocol;
        unsigned char                   protocol;
        unsigned char                   idle;
        unsigned short                  report_desc_length;
        char                            *report_desc;
        unsigned short                  report_length;
        /*
         * use_out_ep - if true, the OUT Endpoint (interrupt out method)
         *              will be used to receive reports from the host
         *              using functions with the "intout" suffix.
         *              Otherwise, the OUT Endpoint will not be configured
         *              and the SETUP/SET_REPORT method ("ssreport" suffix)
         *              will be used to receive reports.
         */
        bool                            use_out_ep;

        /* recv report */
        spinlock_t                      read_spinlock;
        wait_queue_head_t               read_queue;
        /* recv report - interrupt out only (use_out_ep == 1) */
        struct list_head                completed_out_req;
        unsigned int                    qlen;
        /* recv report - setup set_report only (use_out_ep == 0) */
        char                            *set_report_buf;
        unsigned int                    set_report_length;

        /* send report */
        spinlock_t                      write_spinlock;
        bool                            write_pending;
        wait_queue_head_t               write_queue;
        struct usb_request              *req;

        int                             minor;
        struct cdev                     cdev;
        struct usb_function             func;

        struct usb_ep                   *in_ep;
        struct usb_ep                   *out_ep;
};

static inline struct f_hidg *func_to_hidg(struct usb_function *f)
{
        return container_of(f, struct f_hidg, func);
}

/*-------------------------------------------------------------------------*/
/*                           Static descriptors                            */

static struct usb_interface_descriptor hidg_interface_desc = {
        .bLength                = sizeof hidg_interface_desc,
        .bDescriptorType        = USB_DT_INTERFACE,
        /* .bInterfaceNumber    = DYNAMIC */
        .bAlternateSetting      = 0,
        /* .bNumEndpoints       = DYNAMIC (depends on use_out_ep) */
        .bInterfaceClass        = USB_CLASS_HID,
        /* .bInterfaceSubClass  = DYNAMIC */
        /* .bInterfaceProtocol  = DYNAMIC */
        /* .iInterface          = DYNAMIC */
};

static struct hid_descriptor hidg_desc = {
        .bLength                        = sizeof hidg_desc,
        .bDescriptorType                = HID_DT_HID,
        .bcdHID                         = cpu_to_le16(0x0101),
        .bCountryCode                   = 0x00,
        .bNumDescriptors                = 0x1,
        /*.desc[0].bDescriptorType      = DYNAMIC */
        /*.desc[0].wDescriptorLenght    = DYNAMIC */
};

/* Super-Speed Support */

static struct usb_endpoint_descriptor hidg_ss_in_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_IN,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 4, /* FIXME: Add this field in the
                                      * HID gadget configuration?
                                      * (struct hidg_func_descriptor)
                                      */
};

static struct usb_ss_ep_comp_descriptor hidg_ss_in_comp_desc = {
        .bLength                = sizeof(hidg_ss_in_comp_desc),
        .bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,

        /* .bMaxBurst           = 0, */
        /* .bmAttributes        = 0, */
        /* .wBytesPerInterval   = DYNAMIC */
};

static struct usb_endpoint_descriptor hidg_ss_out_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_OUT,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 4, /* FIXME: Add this field in the
                                      * HID gadget configuration?
                                      * (struct hidg_func_descriptor)
                                      */
};

static struct usb_ss_ep_comp_descriptor hidg_ss_out_comp_desc = {
        .bLength                = sizeof(hidg_ss_out_comp_desc),
        .bDescriptorType        = USB_DT_SS_ENDPOINT_COMP,

        /* .bMaxBurst           = 0, */
        /* .bmAttributes        = 0, */
        /* .wBytesPerInterval   = DYNAMIC */
};

static struct usb_descriptor_header *hidg_ss_descriptors_intout[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_ss_in_ep_desc,
        (struct usb_descriptor_header *)&hidg_ss_in_comp_desc,
        (struct usb_descriptor_header *)&hidg_ss_out_ep_desc,
        (struct usb_descriptor_header *)&hidg_ss_out_comp_desc,
        NULL,
};

static struct usb_descriptor_header *hidg_ss_descriptors_ssreport[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_ss_in_ep_desc,
        (struct usb_descriptor_header *)&hidg_ss_in_comp_desc,
        NULL,
};

/* High-Speed Support */

static struct usb_endpoint_descriptor hidg_hs_in_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_IN,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 4, /* FIXME: Add this field in the
                                      * HID gadget configuration?
                                      * (struct hidg_func_descriptor)
                                      */
};

static struct usb_endpoint_descriptor hidg_hs_out_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_OUT,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 4, /* FIXME: Add this field in the
                                      * HID gadget configuration?
                                      * (struct hidg_func_descriptor)
                                      */
};

static struct usb_descriptor_header *hidg_hs_descriptors_intout[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_hs_in_ep_desc,
        (struct usb_descriptor_header *)&hidg_hs_out_ep_desc,
        NULL,
};

static struct usb_descriptor_header *hidg_hs_descriptors_ssreport[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_hs_in_ep_desc,
        NULL,
};

/* Full-Speed Support */

static struct usb_endpoint_descriptor hidg_fs_in_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_IN,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 10, /* FIXME: Add this field in the
                                       * HID gadget configuration?
                                       * (struct hidg_func_descriptor)
                                       */
};

static struct usb_endpoint_descriptor hidg_fs_out_ep_desc = {
        .bLength                = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType        = USB_DT_ENDPOINT,
        .bEndpointAddress       = USB_DIR_OUT,
        .bmAttributes           = USB_ENDPOINT_XFER_INT,
        /*.wMaxPacketSize       = DYNAMIC */
        .bInterval              = 10, /* FIXME: Add this field in the
                                       * HID gadget configuration?
                                       * (struct hidg_func_descriptor)
                                       */
};

static struct usb_descriptor_header *hidg_fs_descriptors_intout[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_fs_in_ep_desc,
        (struct usb_descriptor_header *)&hidg_fs_out_ep_desc,
        NULL,
};

static struct usb_descriptor_header *hidg_fs_descriptors_ssreport[] = {
        (struct usb_descriptor_header *)&hidg_interface_desc,
        (struct usb_descriptor_header *)&hidg_desc,
        (struct usb_descriptor_header *)&hidg_fs_in_ep_desc,
        NULL,
};

/*-------------------------------------------------------------------------*/
/*                                 Strings                                 */

#define CT_FUNC_HID_IDX 0

static struct usb_string ct_func_string_defs[] = {
        [CT_FUNC_HID_IDX].s     = "HID Interface",
        {},                     /* end of list */
};

static struct usb_gadget_strings ct_func_string_table = {
        .language       = 0x0409,       /* en-US */
        .strings        = ct_func_string_defs,
};

static struct usb_gadget_strings *ct_func_strings[] = {
        &ct_func_string_table,
        NULL,
};

/*-------------------------------------------------------------------------*/
/*                              Char Device                                */

static ssize_t f_hidg_intout_read(struct file *file, char __user *buffer,
                                  size_t count, loff_t *ptr)
{
        struct f_hidg *hidg = file->private_data;
        struct f_hidg_req_list *list;
        struct usb_request *req;
        unsigned long flags;
        int ret;

        if (!count)
                return 0;

        spin_lock_irqsave(&hidg->read_spinlock, flags);

#define READ_COND_INTOUT (!list_empty(&hidg->completed_out_req))

        /* wait for at least one buffer to complete */
        while (!READ_COND_INTOUT) {
                spin_unlock_irqrestore(&hidg->read_spinlock, flags);
                if (file->f_flags & O_NONBLOCK)
                        return -EAGAIN;

                if (wait_event_interruptible(hidg->read_queue, READ_COND_INTOUT))
                        return -ERESTARTSYS;

                spin_lock_irqsave(&hidg->read_spinlock, flags);
        }

        /* pick the first one */
        list = list_first_entry(&hidg->completed_out_req,
                                struct f_hidg_req_list, list);

        /*
         * Remove this from list to protect it from beign free()
         * while host disables our function
         */
        list_del(&list->list);

        req = list->req;
        count = min_t(unsigned int, count, req->actual - list->pos);
        spin_unlock_irqrestore(&hidg->read_spinlock, flags);

        /* copy to user outside spinlock */
        count -= copy_to_user(buffer, req->buf + list->pos, count);
        list->pos += count;

        /*
         * if this request is completely handled and transfered to
         * userspace, remove its entry from the list and requeue it
         * again. Otherwise, we will revisit it again upon the next
         * call, taking into account its current read position.
         */
        if (list->pos == req->actual) {
                kfree(list);

                req->length = hidg->report_length;
                ret = usb_ep_queue(hidg->out_ep, req, GFP_KERNEL);
                if (ret < 0) {
                        free_ep_req(hidg->out_ep, req);
                        return ret;
                }
        } else {
                spin_lock_irqsave(&hidg->read_spinlock, flags);
                list_add(&list->list, &hidg->completed_out_req);
                spin_unlock_irqrestore(&hidg->read_spinlock, flags);

                wake_up(&hidg->read_queue);
        }

        return count;
}

#define READ_COND_SSREPORT (hidg->set_report_buf != NULL)

static ssize_t f_hidg_ssreport_read(struct file *file, char __user *buffer,
                                    size_t count, loff_t *ptr)
{
        struct f_hidg *hidg = file->private_data;
        char *tmp_buf = NULL;
        unsigned long flags;

        if (!count)
                return 0;

        spin_lock_irqsave(&hidg->read_spinlock, flags);

        while (!READ_COND_SSREPORT) {
                spin_unlock_irqrestore(&hidg->read_spinlock, flags);
                if (file->f_flags & O_NONBLOCK)
                        return -EAGAIN;

                if (wait_event_interruptible(hidg->read_queue, READ_COND_SSREPORT))
                        return -ERESTARTSYS;

                spin_lock_irqsave(&hidg->read_spinlock, flags);
        }

        count = min_t(unsigned int, count, hidg->set_report_length);
        tmp_buf = hidg->set_report_buf;
        hidg->set_report_buf = NULL;

        spin_unlock_irqrestore(&hidg->read_spinlock, flags);

        if (tmp_buf != NULL) {
                count -= copy_to_user(buffer, tmp_buf, count);
                kfree(tmp_buf);
        } else {
                count = -ENOMEM;
        }

        wake_up(&hidg->read_queue);

        return count;
}

static ssize_t f_hidg_read(struct file *file, char __user *buffer,
                           size_t count, loff_t *ptr)
{
        struct f_hidg *hidg = file->private_data;

        if (hidg->use_out_ep)
                return f_hidg_intout_read(file, buffer, count, ptr);
        else
                return f_hidg_ssreport_read(file, buffer, count, ptr);
}

static void f_hidg_req_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_hidg *hidg = (struct f_hidg *)ep->driver_data;
        unsigned long flags;

        if (req->status != 0) {
                ERROR(hidg->func.config->cdev,
                        "End Point Request ERROR: %d\n", req->status);
        }

        spin_lock_irqsave(&hidg->write_spinlock, flags);
        hidg->write_pending = 0;
        spin_unlock_irqrestore(&hidg->write_spinlock, flags);
        wake_up(&hidg->write_queue);
}

static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
                            size_t count, loff_t *offp)
{
        struct f_hidg *hidg  = file->private_data;
        struct usb_request *req;
        unsigned long flags;
        ssize_t status = -ENOMEM;

        spin_lock_irqsave(&hidg->write_spinlock, flags);

        if (!hidg->req) {
                spin_unlock_irqrestore(&hidg->write_spinlock, flags);
                return -ESHUTDOWN;
        }

#define WRITE_COND (!hidg->write_pending)
try_again:
        /* write queue */
        while (!WRITE_COND) {
                spin_unlock_irqrestore(&hidg->write_spinlock, flags);
                if (file->f_flags & O_NONBLOCK)
                        return -EAGAIN;

                if (wait_event_interruptible_exclusive(
                                hidg->write_queue, WRITE_COND))
                        return -ERESTARTSYS;

                spin_lock_irqsave(&hidg->write_spinlock, flags);
        }

        hidg->write_pending = 1;
        req = hidg->req;
        count  = min_t(unsigned, count, hidg->report_length);

        spin_unlock_irqrestore(&hidg->write_spinlock, flags);

        if (!req) {
                ERROR(hidg->func.config->cdev, "hidg->req is NULL\n");
                status = -ESHUTDOWN;
                goto release_write_pending;
        }

        status = copy_from_user(req->buf, buffer, count);
        if (status != 0) {
                ERROR(hidg->func.config->cdev,
                        "copy_from_user error\n");
                status = -EINVAL;
                goto release_write_pending;
        }

        spin_lock_irqsave(&hidg->write_spinlock, flags);

        /* when our function has been disabled by host */
        if (!hidg->req) {
                free_ep_req(hidg->in_ep, req);
                /*
                 * TODO
                 * Should we fail with error here?
                 */
                goto try_again;
        }

        req->status   = 0;
        req->zero     = 0;
        req->length   = count;
        req->complete = f_hidg_req_complete;
        req->context  = hidg;

        spin_unlock_irqrestore(&hidg->write_spinlock, flags);

        if (!hidg->in_ep->enabled) {
                ERROR(hidg->func.config->cdev, "in_ep is disabled\n");
                status = -ESHUTDOWN;
                goto release_write_pending;
        }

        status = usb_ep_queue(hidg->in_ep, req, GFP_ATOMIC);
        if (status < 0)
                goto release_write_pending;
        else
                status = count;

        return status;
release_write_pending:
        spin_lock_irqsave(&hidg->write_spinlock, flags);
        hidg->write_pending = 0;
        spin_unlock_irqrestore(&hidg->write_spinlock, flags);

        wake_up(&hidg->write_queue);

        return status;
}

static __poll_t f_hidg_poll(struct file *file, poll_table *wait)
{
        struct f_hidg   *hidg  = file->private_data;
        __poll_t        ret = 0;

        poll_wait(file, &hidg->read_queue, wait);
        poll_wait(file, &hidg->write_queue, wait);

        if (WRITE_COND)
                ret |= EPOLLOUT | EPOLLWRNORM;

        if (hidg->use_out_ep) {
                if (READ_COND_INTOUT)
                        ret |= EPOLLIN | EPOLLRDNORM;
        } else {
                if (READ_COND_SSREPORT)
                        ret |= EPOLLIN | EPOLLRDNORM;
        }

        return ret;
}

#undef WRITE_COND
#undef READ_COND_SSREPORT
#undef READ_COND_INTOUT

static int f_hidg_release(struct inode *inode, struct file *fd)
{
        fd->private_data = NULL;
        return 0;
}

static int f_hidg_open(struct inode *inode, struct file *fd)
{
        struct f_hidg *hidg =
                container_of(inode->i_cdev, struct f_hidg, cdev);

        fd->private_data = hidg;

        return 0;
}

/*-------------------------------------------------------------------------*/
/*                                usb_function                             */

static inline struct usb_request *hidg_alloc_ep_req(struct usb_ep *ep,
                                                    unsigned length)
{
        return alloc_ep_req(ep, length);
}

static void hidg_intout_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_hidg *hidg = (struct f_hidg *) req->context;
        struct usb_composite_dev *cdev = hidg->func.config->cdev;
        struct f_hidg_req_list *req_list;
        unsigned long flags;

        switch (req->status) {
        case 0:
                req_list = kzalloc(sizeof(*req_list), GFP_ATOMIC);
                if (!req_list) {
                        ERROR(cdev, "Unable to allocate mem for req_list\n");
                        goto free_req;
                }

                req_list->req = req;

                spin_lock_irqsave(&hidg->read_spinlock, flags);
                list_add_tail(&req_list->list, &hidg->completed_out_req);
                spin_unlock_irqrestore(&hidg->read_spinlock, flags);

                wake_up(&hidg->read_queue);
                break;
        default:
                ERROR(cdev, "Set report failed %d\n", req->status);
                fallthrough;
        case -ECONNABORTED:             /* hardware forced ep reset */
        case -ECONNRESET:               /* request dequeued */
        case -ESHUTDOWN:                /* disconnect from host */
free_req:
                free_ep_req(ep, req);
                return;
        }
}

static void hidg_ssreport_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_hidg *hidg = (struct f_hidg *)req->context;
        struct usb_composite_dev *cdev = hidg->func.config->cdev;
        char *new_buf = NULL;
        unsigned long flags;

        if (req->status != 0 || req->buf == NULL || req->actual == 0) {
                ERROR(cdev,
                      "%s FAILED: status=%d, buf=%p, actual=%d\n",
                      __func__, req->status, req->buf, req->actual);
                return;
        }

        spin_lock_irqsave(&hidg->read_spinlock, flags);

        new_buf = krealloc(hidg->set_report_buf, req->actual, GFP_ATOMIC);
        if (new_buf == NULL) {
                spin_unlock_irqrestore(&hidg->read_spinlock, flags);
                return;
        }
        hidg->set_report_buf = new_buf;

        hidg->set_report_length = req->actual;
        memcpy(hidg->set_report_buf, req->buf, req->actual);

        spin_unlock_irqrestore(&hidg->read_spinlock, flags);

        wake_up(&hidg->read_queue);
}

static int hidg_setup(struct usb_function *f,
                const struct usb_ctrlrequest *ctrl)
{
        struct f_hidg                   *hidg = func_to_hidg(f);
        struct usb_composite_dev        *cdev = f->config->cdev;
        struct usb_request              *req  = cdev->req;
        int status = 0;
        __u16 value, length;

        value   = __le16_to_cpu(ctrl->wValue);
        length  = __le16_to_cpu(ctrl->wLength);

        VDBG(cdev,
             "%s crtl_request : bRequestType:0x%x bRequest:0x%x Value:0x%x\n",
             __func__, ctrl->bRequestType, ctrl->bRequest, value);

        switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_GET_REPORT):
                VDBG(cdev, "get_report\n");

                /* send an empty report */
                length = min_t(unsigned, length, hidg->report_length);
                memset(req->buf, 0x0, length);

                goto respond;
                break;

        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_GET_PROTOCOL):
                VDBG(cdev, "get_protocol\n");
                length = min_t(unsigned int, length, 1);
                ((u8 *) req->buf)[0] = hidg->protocol;
                goto respond;
                break;

        case ((USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_GET_IDLE):
                VDBG(cdev, "get_idle\n");
                length = min_t(unsigned int, length, 1);
                ((u8 *) req->buf)[0] = hidg->idle;
                goto respond;
                break;

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_SET_REPORT):
                VDBG(cdev, "set_report | wLength=%d\n", ctrl->wLength);
                if (hidg->use_out_ep)
                        goto stall;
                req->complete = hidg_ssreport_complete;
                req->context  = hidg;
                goto respond;
                break;

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_SET_PROTOCOL):
                VDBG(cdev, "set_protocol\n");
                if (value > HID_REPORT_PROTOCOL)
                        goto stall;
                length = 0;
                /*
                 * We assume that programs implementing the Boot protocol
                 * are also compatible with the Report Protocol
                 */
                if (hidg->bInterfaceSubClass == USB_INTERFACE_SUBCLASS_BOOT) {
                        hidg->protocol = value;
                        goto respond;
                }
                goto stall;
                break;

        case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE) << 8
                  | HID_REQ_SET_IDLE):
                VDBG(cdev, "set_idle\n");
                length = 0;
                hidg->idle = value >> 8;
                goto respond;
                break;

        case ((USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_INTERFACE) << 8
                  | USB_REQ_GET_DESCRIPTOR):
                switch (value >> 8) {
                case HID_DT_HID:
                {
                        struct hid_descriptor hidg_desc_copy = hidg_desc;

                        VDBG(cdev, "USB_REQ_GET_DESCRIPTOR: HID\n");
                        hidg_desc_copy.desc[0].bDescriptorType = HID_DT_REPORT;
                        hidg_desc_copy.desc[0].wDescriptorLength =
                                cpu_to_le16(hidg->report_desc_length);

                        length = min_t(unsigned short, length,
                                                   hidg_desc_copy.bLength);
                        memcpy(req->buf, &hidg_desc_copy, length);
                        goto respond;
                        break;
                }
                case HID_DT_REPORT:
                        VDBG(cdev, "USB_REQ_GET_DESCRIPTOR: REPORT\n");
                        length = min_t(unsigned short, length,
                                                   hidg->report_desc_length);
                        memcpy(req->buf, hidg->report_desc, length);
                        goto respond;
                        break;

                default:
                        VDBG(cdev, "Unknown descriptor request 0x%x\n",
                                 value >> 8);
                        goto stall;
                        break;
                }
                break;

        default:
                VDBG(cdev, "Unknown request 0x%x\n",
                         ctrl->bRequest);
                goto stall;
                break;
        }

stall:
        return -EOPNOTSUPP;

respond:
        req->zero = 0;
        req->length = length;
        status = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
        if (status < 0)
                ERROR(cdev, "usb_ep_queue error on ep0 %d\n", value);
        return status;
}

static void hidg_disable(struct usb_function *f)
{
        struct f_hidg *hidg = func_to_hidg(f);
        struct f_hidg_req_list *list, *next;
        unsigned long flags;

        usb_ep_disable(hidg->in_ep);

        if (hidg->out_ep) {
                usb_ep_disable(hidg->out_ep);

                spin_lock_irqsave(&hidg->read_spinlock, flags);
                list_for_each_entry_safe(list, next, &hidg->completed_out_req, list) {
                        free_ep_req(hidg->out_ep, list->req);
                        list_del(&list->list);
                        kfree(list);
                }
                spin_unlock_irqrestore(&hidg->read_spinlock, flags);
        }

        spin_lock_irqsave(&hidg->write_spinlock, flags);
        if (!hidg->write_pending) {
                free_ep_req(hidg->in_ep, hidg->req);
                hidg->write_pending = 1;
        }

        hidg->req = NULL;
        spin_unlock_irqrestore(&hidg->write_spinlock, flags);
}

static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
{
        struct usb_composite_dev                *cdev = f->config->cdev;
        struct f_hidg                           *hidg = func_to_hidg(f);
        struct usb_request                      *req_in = NULL;
        unsigned long                           flags;
        int i, status = 0;

        VDBG(cdev, "hidg_set_alt intf:%d alt:%d\n", intf, alt);

        if (hidg->in_ep != NULL) {
                /* restart endpoint */
                usb_ep_disable(hidg->in_ep);

                status = config_ep_by_speed(f->config->cdev->gadget, f,
                                            hidg->in_ep);
                if (status) {
                        ERROR(cdev, "config_ep_by_speed FAILED!\n");
                        goto fail;
                }
                status = usb_ep_enable(hidg->in_ep);
                if (status < 0) {
                        ERROR(cdev, "Enable IN endpoint FAILED!\n");
                        goto fail;
                }
                hidg->in_ep->driver_data = hidg;

                req_in = hidg_alloc_ep_req(hidg->in_ep, hidg->report_length);
                if (!req_in) {
                        status = -ENOMEM;
                        goto disable_ep_in;
                }
        }

        if (hidg->use_out_ep && hidg->out_ep != NULL) {
                /* restart endpoint */
                usb_ep_disable(hidg->out_ep);

                status = config_ep_by_speed(f->config->cdev->gadget, f,
                                            hidg->out_ep);
                if (status) {
                        ERROR(cdev, "config_ep_by_speed FAILED!\n");
                        goto free_req_in;
                }
                status = usb_ep_enable(hidg->out_ep);
                if (status < 0) {
                        ERROR(cdev, "Enable OUT endpoint FAILED!\n");
                        goto free_req_in;
                }
                hidg->out_ep->driver_data = hidg;

                /*
                 * allocate a bunch of read buffers and queue them all at once.
                 */
                for (i = 0; i < hidg->qlen && status == 0; i++) {
                        struct usb_request *req =
                                        hidg_alloc_ep_req(hidg->out_ep,
                                                          hidg->report_length);
                        if (req) {
                                req->complete = hidg_intout_complete;
                                req->context  = hidg;
                                status = usb_ep_queue(hidg->out_ep, req,
                                                      GFP_ATOMIC);
                                if (status) {
                                        ERROR(cdev, "%s queue req --> %d\n",
                                                hidg->out_ep->name, status);
                                        free_ep_req(hidg->out_ep, req);
                                }
                        } else {
                                status = -ENOMEM;
                                goto disable_out_ep;
                        }
                }
        }

        if (hidg->in_ep != NULL) {
                spin_lock_irqsave(&hidg->write_spinlock, flags);
                hidg->req = req_in;
                hidg->write_pending = 0;
                spin_unlock_irqrestore(&hidg->write_spinlock, flags);

                wake_up(&hidg->write_queue);
        }
        return 0;
disable_out_ep:
        if (hidg->out_ep)
                usb_ep_disable(hidg->out_ep);
free_req_in:
        if (req_in)
                free_ep_req(hidg->in_ep, req_in);

disable_ep_in:
        if (hidg->in_ep)
                usb_ep_disable(hidg->in_ep);

fail:
        return status;
}

static const struct file_operations f_hidg_fops = {
        .owner          = THIS_MODULE,
        .open           = f_hidg_open,
        .release        = f_hidg_release,
        .write          = f_hidg_write,
        .read           = f_hidg_read,
        .poll           = f_hidg_poll,
        .llseek         = noop_llseek,
};

static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_ep           *ep;
        struct f_hidg           *hidg = func_to_hidg(f);
        struct usb_string       *us;
        struct device           *device;
        int                     status;
        dev_t                   dev;

        /* maybe allocate device-global string IDs, and patch descriptors */
        us = usb_gstrings_attach(c->cdev, ct_func_strings,
                                 ARRAY_SIZE(ct_func_string_defs));
        if (IS_ERR(us))
                return PTR_ERR(us);
        hidg_interface_desc.iInterface = us[CT_FUNC_HID_IDX].id;

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

        /* allocate instance-specific endpoints */
        status = -ENODEV;
        ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_in_ep_desc);
        if (!ep)
                goto fail;
        hidg->in_ep = ep;

        hidg->out_ep = NULL;
        if (hidg->use_out_ep) {
                ep = usb_ep_autoconfig(c->cdev->gadget, &hidg_fs_out_ep_desc);
                if (!ep)
                        goto fail;
                hidg->out_ep = ep;
        }

        /* used only if use_out_ep == 1 */
        hidg->set_report_buf = NULL;

        /* set descriptor dynamic values */
        hidg_interface_desc.bInterfaceSubClass = hidg->bInterfaceSubClass;
        hidg_interface_desc.bInterfaceProtocol = hidg->bInterfaceProtocol;
        hidg_interface_desc.bNumEndpoints = hidg->use_out_ep ? 2 : 1;
        hidg->protocol = HID_REPORT_PROTOCOL;
        hidg->idle = 1;
        hidg_ss_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_ss_in_comp_desc.wBytesPerInterval =
                                cpu_to_le16(hidg->report_length);
        hidg_hs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_fs_in_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_ss_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_ss_out_comp_desc.wBytesPerInterval =
                                cpu_to_le16(hidg->report_length);
        hidg_hs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        hidg_fs_out_ep_desc.wMaxPacketSize = cpu_to_le16(hidg->report_length);
        /*
         * We can use hidg_desc struct here but we should not relay
         * that its content won't change after returning from this function.
         */
        hidg_desc.desc[0].bDescriptorType = HID_DT_REPORT;
        hidg_desc.desc[0].wDescriptorLength =
                cpu_to_le16(hidg->report_desc_length);

        hidg_hs_in_ep_desc.bEndpointAddress =
                hidg_fs_in_ep_desc.bEndpointAddress;
        hidg_hs_out_ep_desc.bEndpointAddress =
                hidg_fs_out_ep_desc.bEndpointAddress;

        hidg_ss_in_ep_desc.bEndpointAddress =
                hidg_fs_in_ep_desc.bEndpointAddress;
        hidg_ss_out_ep_desc.bEndpointAddress =
                hidg_fs_out_ep_desc.bEndpointAddress;

        if (hidg->use_out_ep)
                status = usb_assign_descriptors(f,
                        hidg_fs_descriptors_intout,
                        hidg_hs_descriptors_intout,
                        hidg_ss_descriptors_intout,
                        hidg_ss_descriptors_intout);
        else
                status = usb_assign_descriptors(f,
                        hidg_fs_descriptors_ssreport,
                        hidg_hs_descriptors_ssreport,
                        hidg_ss_descriptors_ssreport,
                        hidg_ss_descriptors_ssreport);

        if (status)
                goto fail;

        spin_lock_init(&hidg->write_spinlock);
        hidg->write_pending = 1;
        hidg->req = NULL;
        spin_lock_init(&hidg->read_spinlock);
        init_waitqueue_head(&hidg->write_queue);
        init_waitqueue_head(&hidg->read_queue);
        INIT_LIST_HEAD(&hidg->completed_out_req);

        /* create char device */

        cdev_init(&hidg->cdev, &f_hidg_fops);
        dev = MKDEV(major, hidg->minor);
        status = cdev_add(&hidg->cdev, dev, 1);
        if (status)
                goto fail_free_descs;

        device = device_create(hidg_class, NULL, dev, NULL,
                               "%s%d", "hidg", hidg->minor);
        if (IS_ERR(device)) {
                status = PTR_ERR(device);
                goto del;
        }

        return 0;
del:
        cdev_del(&hidg->cdev);
fail_free_descs:
        usb_free_all_descriptors(f);
fail:
        ERROR(f->config->cdev, "hidg_bind FAILED\n");
        if (hidg->req != NULL)
                free_ep_req(hidg->in_ep, hidg->req);

        return status;
}

static inline int hidg_get_minor(void)
{
        int ret;

        ret = ida_simple_get(&hidg_ida, 0, 0, GFP_KERNEL);
        if (ret >= HIDG_MINORS) {
                ida_simple_remove(&hidg_ida, ret);
                ret = -ENODEV;
        }

        return ret;
}

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

static void hid_attr_release(struct config_item *item)
{
        struct f_hid_opts *opts = to_f_hid_opts(item);

        usb_put_function_instance(&opts->func_inst);
}

static struct configfs_item_operations hidg_item_ops = {
        .release        = hid_attr_release,
};

#define F_HID_OPT(name, prec, limit)                                    \
static ssize_t f_hid_opts_##name##_show(struct config_item *item, char *page)\
{                                                                       \
        struct f_hid_opts *opts = to_f_hid_opts(item);                  \
        int result;                                                     \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        result = sprintf(page, "%d\n", opts->name);                     \
        mutex_unlock(&opts->lock);                                      \
                                                                        \
        return result;                                                  \
}                                                                       \
                                                                        \
static ssize_t f_hid_opts_##name##_store(struct config_item *item,      \
                                         const char *page, size_t len)  \
{                                                                       \
        struct f_hid_opts *opts = to_f_hid_opts(item);                  \
        int ret;                                                        \
        u##prec num;                                                    \
                                                                        \
        mutex_lock(&opts->lock);                                        \
        if (opts->refcnt) {                                             \
                ret = -EBUSY;                                           \
                goto end;                                               \
        }                                                               \
                                                                        \
        ret = kstrtou##prec(page, 0, &num);                             \
        if (ret)                                                        \
                goto end;                                               \
                                                                        \
        if (num > limit) {                                              \
                ret = -EINVAL;                                          \
                goto end;                                               \
        }                                                               \
        opts->name = num;                                               \
        ret = len;                                                      \
                                                                        \
end:                                                                    \
        mutex_unlock(&opts->lock);                                      \
        return ret;                                                     \
}                                                                       \
                                                                        \
CONFIGFS_ATTR(f_hid_opts_, name)

F_HID_OPT(subclass, 8, 255);
F_HID_OPT(protocol, 8, 255);
F_HID_OPT(no_out_endpoint, 8, 1);
F_HID_OPT(report_length, 16, 65535);

static ssize_t f_hid_opts_report_desc_show(struct config_item *item, char *page)
{
        struct f_hid_opts *opts = to_f_hid_opts(item);
        int result;

        mutex_lock(&opts->lock);
        result = opts->report_desc_length;
        memcpy(page, opts->report_desc, opts->report_desc_length);
        mutex_unlock(&opts->lock);

        return result;
}

static ssize_t f_hid_opts_report_desc_store(struct config_item *item,
                                            const char *page, size_t len)
{
        struct f_hid_opts *opts = to_f_hid_opts(item);
        int ret = -EBUSY;
        char *d;

        mutex_lock(&opts->lock);

        if (opts->refcnt)
                goto end;
        if (len > PAGE_SIZE) {
                ret = -ENOSPC;
                goto end;
        }
        d = kmemdup(page, len, GFP_KERNEL);
        if (!d) {
                ret = -ENOMEM;
                goto end;
        }
        kfree(opts->report_desc);
        opts->report_desc = d;
        opts->report_desc_length = len;
        opts->report_desc_alloc = true;
        ret = len;
end:
        mutex_unlock(&opts->lock);
        return ret;
}

CONFIGFS_ATTR(f_hid_opts_, report_desc);

static ssize_t f_hid_opts_dev_show(struct config_item *item, char *page)
{
        struct f_hid_opts *opts = to_f_hid_opts(item);

        return sprintf(page, "%d:%d\n", major, opts->minor);
}

CONFIGFS_ATTR_RO(f_hid_opts_, dev);

static struct configfs_attribute *hid_attrs[] = {
        &f_hid_opts_attr_subclass,
        &f_hid_opts_attr_protocol,
        &f_hid_opts_attr_no_out_endpoint,
        &f_hid_opts_attr_report_length,
        &f_hid_opts_attr_report_desc,
        &f_hid_opts_attr_dev,
        NULL,
};

static const struct config_item_type hid_func_type = {
        .ct_item_ops    = &hidg_item_ops,
        .ct_attrs       = hid_attrs,
        .ct_owner       = THIS_MODULE,
};

static inline void hidg_put_minor(int minor)
{
        ida_simple_remove(&hidg_ida, minor);
}

static void hidg_free_inst(struct usb_function_instance *f)
{
        struct f_hid_opts *opts;

        opts = container_of(f, struct f_hid_opts, func_inst);

        mutex_lock(&hidg_ida_lock);

        hidg_put_minor(opts->minor);
        if (ida_is_empty(&hidg_ida))
                ghid_cleanup();

        mutex_unlock(&hidg_ida_lock);

        if (opts->report_desc_alloc)
                kfree(opts->report_desc);

        kfree(opts);
}

static struct usb_function_instance *hidg_alloc_inst(void)
{
        struct f_hid_opts *opts;
        struct usb_function_instance *ret;
        int status = 0;

        opts = kzalloc(sizeof(*opts), GFP_KERNEL);
        if (!opts)
                return ERR_PTR(-ENOMEM);
        mutex_init(&opts->lock);
        opts->func_inst.free_func_inst = hidg_free_inst;
        ret = &opts->func_inst;

        mutex_lock(&hidg_ida_lock);

        if (ida_is_empty(&hidg_ida)) {
                status = ghid_setup(NULL, HIDG_MINORS);
                if (status)  {
                        ret = ERR_PTR(status);
                        kfree(opts);
                        goto unlock;
                }
        }

        opts->minor = hidg_get_minor();
        if (opts->minor < 0) {
                ret = ERR_PTR(opts->minor);
                kfree(opts);
                if (ida_is_empty(&hidg_ida))
                        ghid_cleanup();
                goto unlock;
        }
        config_group_init_type_name(&opts->func_inst.group, "", &hid_func_type);

unlock:
        mutex_unlock(&hidg_ida_lock);
        return ret;
}

static void hidg_free(struct usb_function *f)
{
        struct f_hidg *hidg;
        struct f_hid_opts *opts;

        hidg = func_to_hidg(f);
        opts = container_of(f->fi, struct f_hid_opts, func_inst);
        kfree(hidg->report_desc);
        kfree(hidg->set_report_buf);
        kfree(hidg);
        mutex_lock(&opts->lock);
        --opts->refcnt;
        mutex_unlock(&opts->lock);
}

static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
{
        struct f_hidg *hidg = func_to_hidg(f);

        device_destroy(hidg_class, MKDEV(major, hidg->minor));
        cdev_del(&hidg->cdev);

        usb_free_all_descriptors(f);
}

static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
{
        struct f_hidg *hidg;
        struct f_hid_opts *opts;

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

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

        mutex_lock(&opts->lock);
        ++opts->refcnt;

        hidg->minor = opts->minor;
        hidg->bInterfaceSubClass = opts->subclass;
        hidg->bInterfaceProtocol = opts->protocol;
        hidg->report_length = opts->report_length;
        hidg->report_desc_length = opts->report_desc_length;
        if (opts->report_desc) {
                hidg->report_desc = kmemdup(opts->report_desc,
                                            opts->report_desc_length,
                                            GFP_KERNEL);
                if (!hidg->report_desc) {
                        kfree(hidg);
                        mutex_unlock(&opts->lock);
                        return ERR_PTR(-ENOMEM);
                }
        }
        hidg->use_out_ep = !opts->no_out_endpoint;

        mutex_unlock(&opts->lock);

        hidg->func.name    = "hid";
        hidg->func.bind    = hidg_bind;
        hidg->func.unbind  = hidg_unbind;
        hidg->func.set_alt = hidg_set_alt;
        hidg->func.disable = hidg_disable;
        hidg->func.setup   = hidg_setup;
        hidg->func.free_func = hidg_free;

        /* this could be made configurable at some point */
        hidg->qlen         = 4;

        return &hidg->func;
}

DECLARE_USB_FUNCTION_INIT(hid, hidg_alloc_inst, hidg_alloc);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Fabien Chouteau");

int ghid_setup(struct usb_gadget *g, int count)
{
        int status;
        dev_t dev;

        hidg_class = class_create(THIS_MODULE, "hidg");
        if (IS_ERR(hidg_class)) {
                status = PTR_ERR(hidg_class);
                hidg_class = NULL;
                return status;
        }

        status = alloc_chrdev_region(&dev, 0, count, "hidg");
        if (status) {
                class_destroy(hidg_class);
                hidg_class = NULL;
                return status;
        }

        major = MAJOR(dev);
        minors = count;

        return 0;
}

void ghid_cleanup(void)
{
        if (major) {
                unregister_chrdev_region(MKDEV(major, 0), minors);
                major = minors = 0;
        }

        class_destroy(hidg_class);
        hidg_class = NULL;
}