// SPDX-License-Identifier: GPL-2.0+
/*
 * f_printer.c - USB printer function driver
 *
 * Copied from drivers/usb/gadget/legacy/printer.c,
 * which was:
 *
 * printer.c -- Printer gadget driver
 *
 * Copyright (C) 2003-2005 David Brownell
 * Copyright (C) 2006 Craig W. Nadler
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/timer.h>
#include <linux/list.h>
#include <linux/interrupt.h>
#include <linux/device.h>
#include <linux/moduleparam.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/types.h>
#include <linux/ctype.h>
#include <linux/cdev.h>

#include <asm/byteorder.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/uaccess.h>
#include <asm/unaligned.h>

#include <linux/usb/ch9.h>
#include <linux/usb/composite.h>
#include <linux/usb/gadget.h>
#include <linux/usb/g_printer.h>

#include "u_printer.h"

#define PRINTER_MINORS          4
#define GET_DEVICE_ID           0
#define GET_PORT_STATUS         1
#define SOFT_RESET              2

static int major, minors;
static struct class *usb_gadget_class;
static DEFINE_IDA(printer_ida);
static DEFINE_MUTEX(printer_ida_lock); /* protects access do printer_ida */

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

struct printer_dev {
        spinlock_t              lock;           /* lock this structure */
        /* lock buffer lists during read/write calls */
        struct mutex            lock_printer_io;
        struct usb_gadget       *gadget;
        s8                      interface;
        struct usb_ep           *in_ep, *out_ep;

        struct list_head        rx_reqs;        /* List of free RX structs */
        struct list_head        rx_reqs_active; /* List of Active RX xfers */
        struct list_head        rx_buffers;     /* List of completed xfers */
        /* wait until there is data to be read. */
        wait_queue_head_t       rx_wait;
        struct list_head        tx_reqs;        /* List of free TX structs */
        struct list_head        tx_reqs_active; /* List of Active TX xfers */
        /* Wait until there are write buffers available to use. */
        wait_queue_head_t       tx_wait;
        /* Wait until all write buffers have been sent. */
        wait_queue_head_t       tx_flush_wait;
        struct usb_request      *current_rx_req;
        size_t                  current_rx_bytes;
        u8                      *current_rx_buf;
        u8                      printer_status;
        u8                      reset_printer;
        int                     minor;
        struct cdev             printer_cdev;
        u8                      printer_cdev_open;
        wait_queue_head_t       wait;
        unsigned                q_len;
        char                    *pnp_string;    /* We don't own memory! */
        struct usb_function     function;
};

static inline struct printer_dev *func_to_printer(struct usb_function *f)
{
        return container_of(f, struct printer_dev, function);
}

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

/*
 * DESCRIPTORS ... most are static, but strings and (full) configuration
 * descriptors are built on demand.
 */

/* holds our biggest descriptor */
#define USB_DESC_BUFSIZE                256
#define USB_BUFSIZE                     8192

static struct usb_interface_descriptor intf_desc = {
        .bLength =              sizeof(intf_desc),
        .bDescriptorType =      USB_DT_INTERFACE,
        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_PRINTER,
        .bInterfaceSubClass =   1,      /* Printer Sub-Class */
        .bInterfaceProtocol =   2,      /* Bi-Directional */
        .iInterface =           0
};

static struct usb_endpoint_descriptor fs_ep_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_IN,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK
};

static struct usb_endpoint_descriptor fs_ep_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bEndpointAddress =     USB_DIR_OUT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK
};

static struct usb_descriptor_header *fs_printer_function[] = {
        (struct usb_descriptor_header *) &intf_desc,
        (struct usb_descriptor_header *) &fs_ep_in_desc,
        (struct usb_descriptor_header *) &fs_ep_out_desc,
        NULL
};

/*
 * usb 2.0 devices need to expose both high speed and full speed
 * descriptors, unless they only run at full speed.
 */

static struct usb_endpoint_descriptor hs_ep_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(512)
};

static struct usb_endpoint_descriptor hs_ep_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(512)
};

static struct usb_descriptor_header *hs_printer_function[] = {
        (struct usb_descriptor_header *) &intf_desc,
        (struct usb_descriptor_header *) &hs_ep_in_desc,
        (struct usb_descriptor_header *) &hs_ep_out_desc,
        NULL
};

/*
 * Added endpoint descriptors for 3.0 devices
 */

static struct usb_endpoint_descriptor ss_ep_in_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor ss_ep_in_comp_desc = {
        .bLength =              sizeof(ss_ep_in_comp_desc),
        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
};

static struct usb_endpoint_descriptor ss_ep_out_desc = {
        .bLength =              USB_DT_ENDPOINT_SIZE,
        .bDescriptorType =      USB_DT_ENDPOINT,
        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize =       cpu_to_le16(1024),
};

static struct usb_ss_ep_comp_descriptor ss_ep_out_comp_desc = {
        .bLength =              sizeof(ss_ep_out_comp_desc),
        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
};

static struct usb_descriptor_header *ss_printer_function[] = {
        (struct usb_descriptor_header *) &intf_desc,
        (struct usb_descriptor_header *) &ss_ep_in_desc,
        (struct usb_descriptor_header *) &ss_ep_in_comp_desc,
        (struct usb_descriptor_header *) &ss_ep_out_desc,
        (struct usb_descriptor_header *) &ss_ep_out_comp_desc,
        NULL
};

/* maxpacket and other transfer characteristics vary by speed. */
static inline struct usb_endpoint_descriptor *ep_desc(struct usb_gadget *gadget,
                                        struct usb_endpoint_descriptor *fs,
                                        struct usb_endpoint_descriptor *hs,
                                        struct usb_endpoint_descriptor *ss)
{
        switch (gadget->speed) {
        case USB_SPEED_SUPER:
                return ss;
        case USB_SPEED_HIGH:
                return hs;
        default:
                return fs;
        }
}

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

static struct usb_request *
printer_req_alloc(struct usb_ep *ep, unsigned len, gfp_t gfp_flags)
{
        struct usb_request      *req;

        req = usb_ep_alloc_request(ep, gfp_flags);

        if (req != NULL) {
                req->length = len;
                req->buf = kmalloc(len, gfp_flags);
                if (req->buf == NULL) {
                        usb_ep_free_request(ep, req);
                        return NULL;
                }
        }

        return req;
}

static void
printer_req_free(struct usb_ep *ep, struct usb_request *req)
{
        if (ep != NULL && req != NULL) {
                kfree(req->buf);
                usb_ep_free_request(ep, req);
        }
}

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

static void rx_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct printer_dev      *dev = ep->driver_data;
        int                     status = req->status;
        unsigned long           flags;

        spin_lock_irqsave(&dev->lock, flags);

        list_del_init(&req->list);      /* Remode from Active List */

        switch (status) {

        /* normal completion */
        case 0:
                if (req->actual > 0) {
                        list_add_tail(&req->list, &dev->rx_buffers);
                        DBG(dev, "G_Printer : rx length %d\n", req->actual);
                } else {
                        list_add(&req->list, &dev->rx_reqs);
                }
                break;

        /* software-driven interface shutdown */
        case -ECONNRESET:               /* unlink */
        case -ESHUTDOWN:                /* disconnect etc */
                VDBG(dev, "rx shutdown, code %d\n", status);
                list_add(&req->list, &dev->rx_reqs);
                break;

        /* for hardware automagic (such as pxa) */
        case -ECONNABORTED:             /* endpoint reset */
                DBG(dev, "rx %s reset\n", ep->name);
                list_add(&req->list, &dev->rx_reqs);
                break;

        /* data overrun */
        case -EOVERFLOW:
                fallthrough;

        default:
                DBG(dev, "rx status %d\n", status);
                list_add(&req->list, &dev->rx_reqs);
                break;
        }

        wake_up_interruptible(&dev->rx_wait);
        spin_unlock_irqrestore(&dev->lock, flags);
}

static void tx_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct printer_dev      *dev = ep->driver_data;

        switch (req->status) {
        default:
                VDBG(dev, "tx err %d\n", req->status);
                fallthrough;
        case -ECONNRESET:               /* unlink */
        case -ESHUTDOWN:                /* disconnect etc */
                break;
        case 0:
                break;
        }

        spin_lock(&dev->lock);
        /* Take the request struct off the active list and put it on the
         * free list.
         */
        list_del_init(&req->list);
        list_add(&req->list, &dev->tx_reqs);
        wake_up_interruptible(&dev->tx_wait);
        if (likely(list_empty(&dev->tx_reqs_active)))
                wake_up_interruptible(&dev->tx_flush_wait);

        spin_unlock(&dev->lock);
}

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

static int
printer_open(struct inode *inode, struct file *fd)
{
        struct printer_dev      *dev;
        unsigned long           flags;
        int                     ret = -EBUSY;

        dev = container_of(inode->i_cdev, struct printer_dev, printer_cdev);

        spin_lock_irqsave(&dev->lock, flags);

        if (dev->interface < 0) {
                spin_unlock_irqrestore(&dev->lock, flags);
                return -ENODEV;
        }

        if (!dev->printer_cdev_open) {
                dev->printer_cdev_open = 1;
                fd->private_data = dev;
                ret = 0;
                /* Change the printer status to show that it's on-line. */
                dev->printer_status |= PRINTER_SELECTED;
        }

        spin_unlock_irqrestore(&dev->lock, flags);

        DBG(dev, "printer_open returned %x\n", ret);
        return ret;
}

static int
printer_close(struct inode *inode, struct file *fd)
{
        struct printer_dev      *dev = fd->private_data;
        unsigned long           flags;

        spin_lock_irqsave(&dev->lock, flags);
        dev->printer_cdev_open = 0;
        fd->private_data = NULL;
        /* Change printer status to show that the printer is off-line. */
        dev->printer_status &= ~PRINTER_SELECTED;
        spin_unlock_irqrestore(&dev->lock, flags);

        DBG(dev, "printer_close\n");

        return 0;
}

/* This function must be called with interrupts turned off. */
static void
setup_rx_reqs(struct printer_dev *dev)
{
        struct usb_request              *req;

        while (likely(!list_empty(&dev->rx_reqs))) {
                int error;

                req = container_of(dev->rx_reqs.next,
                                struct usb_request, list);
                list_del_init(&req->list);

                /* The USB Host sends us whatever amount of data it wants to
                 * so we always set the length field to the full USB_BUFSIZE.
                 * If the amount of data is more than the read() caller asked
                 * for it will be stored in the request buffer until it is
                 * asked for by read().
                 */
                req->length = USB_BUFSIZE;
                req->complete = rx_complete;

                /* here, we unlock, and only unlock, to avoid deadlock. */
                spin_unlock(&dev->lock);
                error = usb_ep_queue(dev->out_ep, req, GFP_ATOMIC);
                spin_lock(&dev->lock);
                if (error) {
                        DBG(dev, "rx submit --> %d\n", error);
                        list_add(&req->list, &dev->rx_reqs);
                        break;
                }
                /* if the req is empty, then add it into dev->rx_reqs_active. */
                else if (list_empty(&req->list))
                        list_add(&req->list, &dev->rx_reqs_active);
        }
}

static ssize_t
printer_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
{
        struct printer_dev              *dev = fd->private_data;
        unsigned long                   flags;
        size_t                          size;
        size_t                          bytes_copied;
        struct usb_request              *req;
        /* This is a pointer to the current USB rx request. */
        struct usb_request              *current_rx_req;
        /* This is the number of bytes in the current rx buffer. */
        size_t                          current_rx_bytes;
        /* This is a pointer to the current rx buffer. */
        u8                              *current_rx_buf;

        if (len == 0)
                return -EINVAL;

        DBG(dev, "printer_read trying to read %d bytes\n", (int)len);

        mutex_lock(&dev->lock_printer_io);
        spin_lock_irqsave(&dev->lock, flags);

        if (dev->interface < 0) {
                spin_unlock_irqrestore(&dev->lock, flags);
                mutex_unlock(&dev->lock_printer_io);
                return -ENODEV;
        }

        /* We will use this flag later to check if a printer reset happened
         * after we turn interrupts back on.
         */
        dev->reset_printer = 0;

        setup_rx_reqs(dev);

        bytes_copied = 0;
        current_rx_req = dev->current_rx_req;
        current_rx_bytes = dev->current_rx_bytes;
        current_rx_buf = dev->current_rx_buf;
        dev->current_rx_req = NULL;
        dev->current_rx_bytes = 0;
        dev->current_rx_buf = NULL;

        /* Check if there is any data in the read buffers. Please note that
         * current_rx_bytes is the number of bytes in the current rx buffer.
         * If it is zero then check if there are any other rx_buffers that
         * are on the completed list. We are only out of data if all rx
         * buffers are empty.
         */
        if ((current_rx_bytes == 0) &&
                        (likely(list_empty(&dev->rx_buffers)))) {
                /* Turn interrupts back on before sleeping. */
                spin_unlock_irqrestore(&dev->lock, flags);

                /*
                 * If no data is available check if this is a NON-Blocking
                 * call or not.
                 */
                if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
                        mutex_unlock(&dev->lock_printer_io);
                        return -EAGAIN;
                }

                /* Sleep until data is available */
                wait_event_interruptible(dev->rx_wait,
                                (likely(!list_empty(&dev->rx_buffers))));
                spin_lock_irqsave(&dev->lock, flags);
        }

        /* We have data to return then copy it to the caller's buffer.*/
        while ((current_rx_bytes || likely(!list_empty(&dev->rx_buffers)))
                        && len) {
                if (current_rx_bytes == 0) {
                        req = container_of(dev->rx_buffers.next,
                                        struct usb_request, list);
                        list_del_init(&req->list);

                        if (req->actual && req->buf) {
                                current_rx_req = req;
                                current_rx_bytes = req->actual;
                                current_rx_buf = req->buf;
                        } else {
                                list_add(&req->list, &dev->rx_reqs);
                                continue;
                        }
                }

                /* Don't leave irqs off while doing memory copies */
                spin_unlock_irqrestore(&dev->lock, flags);

                if (len > current_rx_bytes)
                        size = current_rx_bytes;
                else
                        size = len;

                size -= copy_to_user(buf, current_rx_buf, size);
                bytes_copied += size;
                len -= size;
                buf += size;

                spin_lock_irqsave(&dev->lock, flags);

                /* We've disconnected or reset so return. */
                if (dev->reset_printer) {
                        list_add(&current_rx_req->list, &dev->rx_reqs);
                        spin_unlock_irqrestore(&dev->lock, flags);
                        mutex_unlock(&dev->lock_printer_io);
                        return -EAGAIN;
                }

                /* If we not returning all the data left in this RX request
                 * buffer then adjust the amount of data left in the buffer.
                 * Othewise if we are done with this RX request buffer then
                 * requeue it to get any incoming data from the USB host.
                 */
                if (size < current_rx_bytes) {
                        current_rx_bytes -= size;
                        current_rx_buf += size;
                } else {
                        list_add(&current_rx_req->list, &dev->rx_reqs);
                        current_rx_bytes = 0;
                        current_rx_buf = NULL;
                        current_rx_req = NULL;
                }
        }

        dev->current_rx_req = current_rx_req;
        dev->current_rx_bytes = current_rx_bytes;
        dev->current_rx_buf = current_rx_buf;

        spin_unlock_irqrestore(&dev->lock, flags);
        mutex_unlock(&dev->lock_printer_io);

        DBG(dev, "printer_read returned %d bytes\n", (int)bytes_copied);

        if (bytes_copied)
                return bytes_copied;
        else
                return -EAGAIN;
}

static ssize_t
printer_write(struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
{
        struct printer_dev      *dev = fd->private_data;
        unsigned long           flags;
        size_t                  size;   /* Amount of data in a TX request. */
        size_t                  bytes_copied = 0;
        struct usb_request      *req;
        int                     value;

        DBG(dev, "printer_write trying to send %d bytes\n", (int)len);

        if (len == 0)
                return -EINVAL;

        mutex_lock(&dev->lock_printer_io);
        spin_lock_irqsave(&dev->lock, flags);

        if (dev->interface < 0) {
                spin_unlock_irqrestore(&dev->lock, flags);
                mutex_unlock(&dev->lock_printer_io);
                return -ENODEV;
        }

        /* Check if a printer reset happens while we have interrupts on */
        dev->reset_printer = 0;

        /* Check if there is any available write buffers */
        if (likely(list_empty(&dev->tx_reqs))) {
                /* Turn interrupts back on before sleeping. */
                spin_unlock_irqrestore(&dev->lock, flags);

                /*
                 * If write buffers are available check if this is
                 * a NON-Blocking call or not.
                 */
                if (fd->f_flags & (O_NONBLOCK|O_NDELAY)) {
                        mutex_unlock(&dev->lock_printer_io);
                        return -EAGAIN;
                }

                /* Sleep until a write buffer is available */
                wait_event_interruptible(dev->tx_wait,
                                (likely(!list_empty(&dev->tx_reqs))));
                spin_lock_irqsave(&dev->lock, flags);
        }

        while (likely(!list_empty(&dev->tx_reqs)) && len) {

                if (len > USB_BUFSIZE)
                        size = USB_BUFSIZE;
                else
                        size = len;

                req = container_of(dev->tx_reqs.next, struct usb_request,
                                list);
                list_del_init(&req->list);

                req->complete = tx_complete;
                req->length = size;

                /* Check if we need to send a zero length packet. */
                if (len > size)
                        /* They will be more TX requests so no yet. */
                        req->zero = 0;
                else
                        /* If the data amount is not a multiple of the
                         * maxpacket size then send a zero length packet.
                         */
                        req->zero = ((len % dev->in_ep->maxpacket) == 0);

                /* Don't leave irqs off while doing memory copies */
                spin_unlock_irqrestore(&dev->lock, flags);

                if (copy_from_user(req->buf, buf, size)) {
                        list_add(&req->list, &dev->tx_reqs);
                        mutex_unlock(&dev->lock_printer_io);
                        return bytes_copied;
                }

                bytes_copied += size;
                len -= size;
                buf += size;

                spin_lock_irqsave(&dev->lock, flags);

                /* We've disconnected or reset so free the req and buffer */
                if (dev->reset_printer) {
                        list_add(&req->list, &dev->tx_reqs);
                        spin_unlock_irqrestore(&dev->lock, flags);
                        mutex_unlock(&dev->lock_printer_io);
                        return -EAGAIN;
                }

                list_add(&req->list, &dev->tx_reqs_active);

                /* here, we unlock, and only unlock, to avoid deadlock. */
                spin_unlock(&dev->lock);
                value = usb_ep_queue(dev->in_ep, req, GFP_ATOMIC);
                spin_lock(&dev->lock);
                if (value) {
                        list_del(&req->list);
                        list_add(&req->list, &dev->tx_reqs);
                        spin_unlock_irqrestore(&dev->lock, flags);
                        mutex_unlock(&dev->lock_printer_io);
                        return -EAGAIN;
                }
        }

        spin_unlock_irqrestore(&dev->lock, flags);
        mutex_unlock(&dev->lock_printer_io);

        DBG(dev, "printer_write sent %d bytes\n", (int)bytes_copied);

        if (bytes_copied)
                return bytes_copied;
        else
                return -EAGAIN;
}

static int
printer_fsync(struct file *fd, loff_t start, loff_t end, int datasync)
{
        struct printer_dev      *dev = fd->private_data;
        struct inode *inode = file_inode(fd);
        unsigned long           flags;
        int                     tx_list_empty;

        inode_lock(inode);
        spin_lock_irqsave(&dev->lock, flags);

        if (dev->interface < 0) {
                spin_unlock_irqrestore(&dev->lock, flags);
                inode_unlock(inode);
                return -ENODEV;
        }

        tx_list_empty = (likely(list_empty(&dev->tx_reqs)));
        spin_unlock_irqrestore(&dev->lock, flags);

        if (!tx_list_empty) {
                /* Sleep until all data has been sent */
                wait_event_interruptible(dev->tx_flush_wait,
                                (likely(list_empty(&dev->tx_reqs_active))));
        }
        inode_unlock(inode);

        return 0;
}

static __poll_t
printer_poll(struct file *fd, poll_table *wait)
{
        struct printer_dev      *dev = fd->private_data;
        unsigned long           flags;
        __poll_t                status = 0;

        mutex_lock(&dev->lock_printer_io);
        spin_lock_irqsave(&dev->lock, flags);

        if (dev->interface < 0) {
                spin_unlock_irqrestore(&dev->lock, flags);
                mutex_unlock(&dev->lock_printer_io);
                return EPOLLERR | EPOLLHUP;
        }

        setup_rx_reqs(dev);
        spin_unlock_irqrestore(&dev->lock, flags);
        mutex_unlock(&dev->lock_printer_io);

        poll_wait(fd, &dev->rx_wait, wait);
        poll_wait(fd, &dev->tx_wait, wait);

        spin_lock_irqsave(&dev->lock, flags);
        if (likely(!list_empty(&dev->tx_reqs)))
                status |= EPOLLOUT | EPOLLWRNORM;

        if (likely(dev->current_rx_bytes) ||
                        likely(!list_empty(&dev->rx_buffers)))
                status |= EPOLLIN | EPOLLRDNORM;

        spin_unlock_irqrestore(&dev->lock, flags);

        return status;
}

static long
printer_ioctl(struct file *fd, unsigned int code, unsigned long arg)
{
        struct printer_dev      *dev = fd->private_data;
        unsigned long           flags;
        int                     status = 0;

        DBG(dev, "printer_ioctl: cmd=0x%4.4x, arg=%lu\n", code, arg);

        /* handle ioctls */

        spin_lock_irqsave(&dev->lock, flags);

        if (dev->interface < 0) {
                spin_unlock_irqrestore(&dev->lock, flags);
                return -ENODEV;
        }

        switch (code) {
        case GADGET_GET_PRINTER_STATUS:
                status = (int)dev->printer_status;
                break;
        case GADGET_SET_PRINTER_STATUS:
                dev->printer_status = (u8)arg;
                break;
        default:
                /* could not handle ioctl */
                DBG(dev, "printer_ioctl: ERROR cmd=0x%4.4xis not supported\n",
                                code);
                status = -ENOTTY;
        }

        spin_unlock_irqrestore(&dev->lock, flags);

        return status;
}

/* used after endpoint configuration */
static const struct file_operations printer_io_operations = {
        .owner =        THIS_MODULE,
        .open =         printer_open,
        .read =         printer_read,
        .write =        printer_write,
        .fsync =        printer_fsync,
        .poll =         printer_poll,
        .unlocked_ioctl = printer_ioctl,
        .release =      printer_close,
        .llseek =       noop_llseek,
};

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

static int
set_printer_interface(struct printer_dev *dev)
{
        int                     result = 0;

        dev->in_ep->desc = ep_desc(dev->gadget, &fs_ep_in_desc, &hs_ep_in_desc,
                                &ss_ep_in_desc);
        dev->in_ep->driver_data = dev;

        dev->out_ep->desc = ep_desc(dev->gadget, &fs_ep_out_desc,
                                    &hs_ep_out_desc, &ss_ep_out_desc);
        dev->out_ep->driver_data = dev;

        result = usb_ep_enable(dev->in_ep);
        if (result != 0) {
                DBG(dev, "enable %s --> %d\n", dev->in_ep->name, result);
                goto done;
        }

        result = usb_ep_enable(dev->out_ep);
        if (result != 0) {
                DBG(dev, "enable %s --> %d\n", dev->in_ep->name, result);
                goto done;
        }

done:
        /* on error, disable any endpoints  */
        if (result != 0) {
                (void) usb_ep_disable(dev->in_ep);
                (void) usb_ep_disable(dev->out_ep);
                dev->in_ep->desc = NULL;
                dev->out_ep->desc = NULL;
        }

        /* caller is responsible for cleanup on error */
        return result;
}

static void printer_reset_interface(struct printer_dev *dev)
{
        unsigned long   flags;

        if (dev->interface < 0)
                return;

        DBG(dev, "%s\n", __func__);

        if (dev->in_ep->desc)
                usb_ep_disable(dev->in_ep);

        if (dev->out_ep->desc)
                usb_ep_disable(dev->out_ep);

        spin_lock_irqsave(&dev->lock, flags);
        dev->in_ep->desc = NULL;
        dev->out_ep->desc = NULL;
        dev->interface = -1;
        spin_unlock_irqrestore(&dev->lock, flags);
}

/* Change our operational Interface. */
static int set_interface(struct printer_dev *dev, unsigned number)
{
        int                     result = 0;

        /* Free the current interface */
        printer_reset_interface(dev);

        result = set_printer_interface(dev);
        if (result)
                printer_reset_interface(dev);
        else
                dev->interface = number;

        if (!result)
                INFO(dev, "Using interface %x\n", number);

        return result;
}

static void printer_soft_reset(struct printer_dev *dev)
{
        struct usb_request      *req;

        INFO(dev, "Received Printer Reset Request\n");

        if (usb_ep_disable(dev->in_ep))
                DBG(dev, "Failed to disable USB in_ep\n");
        if (usb_ep_disable(dev->out_ep))
                DBG(dev, "Failed to disable USB out_ep\n");

        if (dev->current_rx_req != NULL) {
                list_add(&dev->current_rx_req->list, &dev->rx_reqs);
                dev->current_rx_req = NULL;
        }
        dev->current_rx_bytes = 0;
        dev->current_rx_buf = NULL;
        dev->reset_printer = 1;

        while (likely(!(list_empty(&dev->rx_buffers)))) {
                req = container_of(dev->rx_buffers.next, struct usb_request,
                                list);
                list_del_init(&req->list);
                list_add(&req->list, &dev->rx_reqs);
        }

        while (likely(!(list_empty(&dev->rx_reqs_active)))) {
                req = container_of(dev->rx_buffers.next, struct usb_request,
                                list);
                list_del_init(&req->list);
                list_add(&req->list, &dev->rx_reqs);
        }

        while (likely(!(list_empty(&dev->tx_reqs_active)))) {
                req = container_of(dev->tx_reqs_active.next,
                                struct usb_request, list);
                list_del_init(&req->list);
                list_add(&req->list, &dev->tx_reqs);
        }

        if (usb_ep_enable(dev->in_ep))
                DBG(dev, "Failed to enable USB in_ep\n");
        if (usb_ep_enable(dev->out_ep))
                DBG(dev, "Failed to enable USB out_ep\n");

        wake_up_interruptible(&dev->rx_wait);
        wake_up_interruptible(&dev->tx_wait);
        wake_up_interruptible(&dev->tx_flush_wait);
}

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

static bool gprinter_req_match(struct usb_function *f,
                               const struct usb_ctrlrequest *ctrl,
                               bool config0)
{
        struct printer_dev      *dev = func_to_printer(f);
        u16                     w_index = le16_to_cpu(ctrl->wIndex);
        u16                     w_value = le16_to_cpu(ctrl->wValue);
        u16                     w_length = le16_to_cpu(ctrl->wLength);

        if (config0)
                return false;

        if ((ctrl->bRequestType & USB_RECIP_MASK) != USB_RECIP_INTERFACE ||
            (ctrl->bRequestType & USB_TYPE_MASK) != USB_TYPE_CLASS)
                return false;

        switch (ctrl->bRequest) {
        case GET_DEVICE_ID:
                w_index >>= 8;
                if (USB_DIR_IN & ctrl->bRequestType)
                        break;
                return false;
        case GET_PORT_STATUS:
                if (!w_value && w_length == 1 &&
                    (USB_DIR_IN & ctrl->bRequestType))
                        break;
                return false;
        case SOFT_RESET:
                if (!w_value && !w_length &&
                   !(USB_DIR_IN & ctrl->bRequestType))
                        break;
                fallthrough;
        default:
                return false;
        }
        return w_index == dev->interface;
}

/*
 * The setup() callback implements all the ep0 functionality that's not
 * handled lower down.
 */
static int printer_func_setup(struct usb_function *f,
                const struct usb_ctrlrequest *ctrl)
{
        struct printer_dev *dev = func_to_printer(f);
        struct usb_composite_dev *cdev = f->config->cdev;
        struct usb_request      *req = cdev->req;
        u8                      *buf = req->buf;
        int                     value = -EOPNOTSUPP;
        u16                     wIndex = le16_to_cpu(ctrl->wIndex);
        u16                     wValue = le16_to_cpu(ctrl->wValue);
        u16                     wLength = le16_to_cpu(ctrl->wLength);

        DBG(dev, "ctrl req%02x.%02x v%04x i%04x l%d\n",
                ctrl->bRequestType, ctrl->bRequest, wValue, wIndex, wLength);

        switch (ctrl->bRequestType&USB_TYPE_MASK) {
        case USB_TYPE_CLASS:
                switch (ctrl->bRequest) {
                case GET_DEVICE_ID: /* Get the IEEE-1284 PNP String */
                        /* Only one printer interface is supported. */
                        if ((wIndex>>8) != dev->interface)
                                break;

                        if (!dev->pnp_string) {
                                value = 0;
                                break;
                        }
                        value = strlen(dev->pnp_string);
                        buf[0] = (value >> 8) & 0xFF;
                        buf[1] = value & 0xFF;
                        memcpy(buf + 2, dev->pnp_string, value);
                        DBG(dev, "1284 PNP String: %x %s\n", value,

                            dev->pnp_string);
                        break;

                case GET_PORT_STATUS: /* Get Port Status */
                        /* Only one printer interface is supported. */
                        if (wIndex != dev->interface)
                                break;

                        buf[0] = dev->printer_status;
                        value = min_t(u16, wLength, 1);
                        break;

                case SOFT_RESET: /* Soft Reset */
                        /* Only one printer interface is supported. */
                        if (wIndex != dev->interface)
                                break;

                        printer_soft_reset(dev);

                        value = 0;
                        break;

                default:
                        goto unknown;
                }
                break;

        default:
unknown:
                VDBG(dev,
                        "unknown ctrl req%02x.%02x v%04x i%04x l%d\n",
                        ctrl->bRequestType, ctrl->bRequest,
                        wValue, wIndex, wLength);
                break;
        }
        /* host either stalls (value < 0) or reports success */
        if (value >= 0) {
                req->length = value;
                req->zero = value < wLength;
                value = usb_ep_queue(cdev->gadget->ep0, req, GFP_ATOMIC);
                if (value < 0) {
                        ERROR(dev, "%s:%d Error!\n", __func__, __LINE__);
                        req->status = 0;
                }
        }
        return value;
}

static int printer_func_bind(struct usb_configuration *c,
                struct usb_function *f)
{
        struct usb_gadget *gadget = c->cdev->gadget;
        struct printer_dev *dev = func_to_printer(f);
        struct device *pdev;
        struct usb_composite_dev *cdev = c->cdev;
        struct usb_ep *in_ep;
        struct usb_ep *out_ep = NULL;
        struct usb_request *req;
        dev_t devt;
        int id;
        int ret;
        u32 i;

        id = usb_interface_id(c, f);
        if (id < 0)
                return id;
        intf_desc.bInterfaceNumber = id;

        /* finish hookup to lower layer ... */
        dev->gadget = gadget;

        /* all we really need is bulk IN/OUT */
        in_ep = usb_ep_autoconfig(cdev->gadget, &fs_ep_in_desc);
        if (!in_ep) {
autoconf_fail:
                dev_err(&cdev->gadget->dev, "can't autoconfigure on %s\n",
                        cdev->gadget->name);
                return -ENODEV;
        }

        out_ep = usb_ep_autoconfig(cdev->gadget, &fs_ep_out_desc);
        if (!out_ep)
                goto autoconf_fail;

        /* assumes that all endpoints are dual-speed */
        hs_ep_in_desc.bEndpointAddress = fs_ep_in_desc.bEndpointAddress;
        hs_ep_out_desc.bEndpointAddress = fs_ep_out_desc.bEndpointAddress;
        ss_ep_in_desc.bEndpointAddress = fs_ep_in_desc.bEndpointAddress;
        ss_ep_out_desc.bEndpointAddress = fs_ep_out_desc.bEndpointAddress;

        ret = usb_assign_descriptors(f, fs_printer_function,
                        hs_printer_function, ss_printer_function, NULL);
        if (ret)
                return ret;

        dev->in_ep = in_ep;
        dev->out_ep = out_ep;

        ret = -ENOMEM;
        for (i = 0; i < dev->q_len; i++) {
                req = printer_req_alloc(dev->in_ep, USB_BUFSIZE, GFP_KERNEL);
                if (!req)
                        goto fail_tx_reqs;
                list_add(&req->list, &dev->tx_reqs);
        }

        for (i = 0; i < dev->q_len; i++) {
                req = printer_req_alloc(dev->out_ep, USB_BUFSIZE, GFP_KERNEL);
                if (!req)
                        goto fail_rx_reqs;
                list_add(&req->list, &dev->rx_reqs);
        }

        /* Setup the sysfs files for the printer gadget. */
        devt = MKDEV(major, dev->minor);
        pdev = device_create(usb_gadget_class, NULL, devt,
                                  NULL, "g_printer%d", dev->minor);
        if (IS_ERR(pdev)) {
                ERROR(dev, "Failed to create device: g_printer\n");
                ret = PTR_ERR(pdev);
                goto fail_rx_reqs;
        }

        /*
         * Register a character device as an interface to a user mode
         * program that handles the printer specific functionality.
         */
        cdev_init(&dev->printer_cdev, &printer_io_operations);
        dev->printer_cdev.owner = THIS_MODULE;
        ret = cdev_add(&dev->printer_cdev, devt, 1);
        if (ret) {
                ERROR(dev, "Failed to open char device\n");
                goto fail_cdev_add;
        }

        return 0;

fail_cdev_add:
        device_destroy(usb_gadget_class, devt);

fail_rx_reqs:
        while (!list_empty(&dev->rx_reqs)) {
                req = container_of(dev->rx_reqs.next, struct usb_request, list);
                list_del(&req->list);
                printer_req_free(dev->out_ep, req);
        }

fail_tx_reqs:
        while (!list_empty(&dev->tx_reqs)) {
                req = container_of(dev->tx_reqs.next, struct usb_request, list);
                list_del(&req->list);
                printer_req_free(dev->in_ep, req);
        }

        return ret;

}

static int printer_func_set_alt(struct usb_function *f,
                unsigned intf, unsigned alt)
{
        struct printer_dev *dev = func_to_printer(f);
        int ret = -ENOTSUPP;

        if (!alt)
                ret = set_interface(dev, intf);

        return ret;
}

static void printer_func_disable(struct usb_function *f)
{
        struct printer_dev *dev = func_to_printer(f);

        DBG(dev, "%s\n", __func__);

        printer_reset_interface(dev);
}

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

static void printer_attr_release(struct config_item *item)
{
        struct f_printer_opts *opts = to_f_printer_opts(item);

        usb_put_function_instance(&opts->func_inst);
}

static struct configfs_item_operations printer_item_ops = {
        .release        = printer_attr_release,
};

static ssize_t f_printer_opts_pnp_string_show(struct config_item *item,
                                              char *page)
{
        struct f_printer_opts *opts = to_f_printer_opts(item);
        int result = 0;

        mutex_lock(&opts->lock);
        if (!opts->pnp_string)
                goto unlock;

        result = strlcpy(page, opts->pnp_string, PAGE_SIZE);
        if (result >= PAGE_SIZE) {
                result = PAGE_SIZE;
        } else if (page[result - 1] != '\n' && result + 1 < PAGE_SIZE) {
                page[result++] = '\n';
                page[result] = '\0';
        }

unlock:
        mutex_unlock(&opts->lock);

        return result;
}

static ssize_t f_printer_opts_pnp_string_store(struct config_item *item,
                                               const char *page, size_t len)
{
        struct f_printer_opts *opts = to_f_printer_opts(item);
        char *new_pnp;
        int result;

        mutex_lock(&opts->lock);

        new_pnp = kstrndup(page, len, GFP_KERNEL);
        if (!new_pnp) {
                result = -ENOMEM;
                goto unlock;
        }

        if (opts->pnp_string_allocated)
                kfree(opts->pnp_string);

        opts->pnp_string_allocated = true;
        opts->pnp_string = new_pnp;
        result = len;
unlock:
        mutex_unlock(&opts->lock);

        return result;
}

CONFIGFS_ATTR(f_printer_opts_, pnp_string);

static ssize_t f_printer_opts_q_len_show(struct config_item *item,
                                         char *page)
{
        struct f_printer_opts *opts = to_f_printer_opts(item);
        int result;

        mutex_lock(&opts->lock);
        result = sprintf(page, "%d\n", opts->q_len);
        mutex_unlock(&opts->lock);

        return result;
}

static ssize_t f_printer_opts_q_len_store(struct config_item *item,
                                          const char *page, size_t len)
{
        struct f_printer_opts *opts = to_f_printer_opts(item);
        int ret;
        u16 num;

        mutex_lock(&opts->lock);
        if (opts->refcnt) {
                ret = -EBUSY;
                goto end;
        }

        ret = kstrtou16(page, 0, &num);
        if (ret)
                goto end;

        opts->q_len = (unsigned)num;
        ret = len;
end:
        mutex_unlock(&opts->lock);
        return ret;
}

CONFIGFS_ATTR(f_printer_opts_, q_len);

static struct configfs_attribute *printer_attrs[] = {
        &f_printer_opts_attr_pnp_string,
        &f_printer_opts_attr_q_len,
        NULL,
};

static const struct config_item_type printer_func_type = {
        .ct_item_ops    = &printer_item_ops,
        .ct_attrs       = printer_attrs,
        .ct_owner       = THIS_MODULE,
};

static inline int gprinter_get_minor(void)
{
        int ret;

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

        return ret;
}

static inline void gprinter_put_minor(int minor)
{
        ida_simple_remove(&printer_ida, minor);
}

static int gprinter_setup(int);
static void gprinter_cleanup(void);

static void gprinter_free_inst(struct usb_function_instance *f)
{
        struct f_printer_opts *opts;

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

        mutex_lock(&printer_ida_lock);

        gprinter_put_minor(opts->minor);
        if (ida_is_empty(&printer_ida))
                gprinter_cleanup();

        mutex_unlock(&printer_ida_lock);

        if (opts->pnp_string_allocated)
                kfree(opts->pnp_string);
        kfree(opts);
}

static struct usb_function_instance *gprinter_alloc_inst(void)
{
        struct f_printer_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 = gprinter_free_inst;
        ret = &opts->func_inst;

        mutex_lock(&printer_ida_lock);

        if (ida_is_empty(&printer_ida)) {
                status = gprinter_setup(PRINTER_MINORS);
                if (status) {
                        ret = ERR_PTR(status);
                        kfree(opts);
                        goto unlock;
                }
        }

        opts->minor = gprinter_get_minor();
        if (opts->minor < 0) {
                ret = ERR_PTR(opts->minor);
                kfree(opts);
                if (ida_is_empty(&printer_ida))
                        gprinter_cleanup();
                goto unlock;
        }
        config_group_init_type_name(&opts->func_inst.group, "",
                                    &printer_func_type);

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

static void gprinter_free(struct usb_function *f)
{
        struct printer_dev *dev = func_to_printer(f);
        struct f_printer_opts *opts;

        opts = container_of(f->fi, struct f_printer_opts, func_inst);
        kfree(dev);
        mutex_lock(&opts->lock);
        --opts->refcnt;
        mutex_unlock(&opts->lock);
}

static void printer_func_unbind(struct usb_configuration *c,
                struct usb_function *f)
{
        struct printer_dev      *dev;
        struct usb_request      *req;

        dev = func_to_printer(f);

        device_destroy(usb_gadget_class, MKDEV(major, dev->minor));

        /* Remove Character Device */
        cdev_del(&dev->printer_cdev);

        /* we must already have been disconnected ... no i/o may be active */
        WARN_ON(!list_empty(&dev->tx_reqs_active));
        WARN_ON(!list_empty(&dev->rx_reqs_active));

        /* Free all memory for this driver. */
        while (!list_empty(&dev->tx_reqs)) {
                req = container_of(dev->tx_reqs.next, struct usb_request,
                                list);
                list_del(&req->list);
                printer_req_free(dev->in_ep, req);
        }

        if (dev->current_rx_req != NULL)
                printer_req_free(dev->out_ep, dev->current_rx_req);

        while (!list_empty(&dev->rx_reqs)) {
                req = container_of(dev->rx_reqs.next,
                                struct usb_request, list);
                list_del(&req->list);
                printer_req_free(dev->out_ep, req);
        }

        while (!list_empty(&dev->rx_buffers)) {
                req = container_of(dev->rx_buffers.next,
                                struct usb_request, list);
                list_del(&req->list);
                printer_req_free(dev->out_ep, req);
        }
        usb_free_all_descriptors(f);
}

static struct usb_function *gprinter_alloc(struct usb_function_instance *fi)
{
        struct printer_dev      *dev;
        struct f_printer_opts   *opts;

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

        mutex_lock(&opts->lock);
        if (opts->minor >= minors) {
                mutex_unlock(&opts->lock);
                return ERR_PTR(-ENOENT);
        }

        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
        if (!dev) {
                mutex_unlock(&opts->lock);
                return ERR_PTR(-ENOMEM);
        }

        ++opts->refcnt;
        dev->minor = opts->minor;
        dev->pnp_string = opts->pnp_string;
        dev->q_len = opts->q_len;
        mutex_unlock(&opts->lock);

        dev->function.name = "printer";
        dev->function.bind = printer_func_bind;
        dev->function.setup = printer_func_setup;
        dev->function.unbind = printer_func_unbind;
        dev->function.set_alt = printer_func_set_alt;
        dev->function.disable = printer_func_disable;
        dev->function.req_match = gprinter_req_match;
        dev->function.free_func = gprinter_free;

        INIT_LIST_HEAD(&dev->tx_reqs);
        INIT_LIST_HEAD(&dev->rx_reqs);
        INIT_LIST_HEAD(&dev->rx_buffers);
        INIT_LIST_HEAD(&dev->tx_reqs_active);
        INIT_LIST_HEAD(&dev->rx_reqs_active);

        spin_lock_init(&dev->lock);
        mutex_init(&dev->lock_printer_io);
        init_waitqueue_head(&dev->rx_wait);
        init_waitqueue_head(&dev->tx_wait);
        init_waitqueue_head(&dev->tx_flush_wait);

        dev->interface = -1;
        dev->printer_cdev_open = 0;
        dev->printer_status = PRINTER_NOT_ERROR;
        dev->current_rx_req = NULL;
        dev->current_rx_bytes = 0;
        dev->current_rx_buf = NULL;

        return &dev->function;
}

DECLARE_USB_FUNCTION_INIT(printer, gprinter_alloc_inst, gprinter_alloc);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Craig Nadler");

static int gprinter_setup(int count)
{
        int status;
        dev_t devt;

        usb_gadget_class = class_create(THIS_MODULE, "usb_printer_gadget");
        if (IS_ERR(usb_gadget_class)) {
                status = PTR_ERR(usb_gadget_class);
                usb_gadget_class = NULL;
                pr_err("unable to create usb_gadget class %d\n", status);
                return status;
        }

        status = alloc_chrdev_region(&devt, 0, count, "USB printer gadget");
        if (status) {
                pr_err("alloc_chrdev_region %d\n", status);
                class_destroy(usb_gadget_class);
                usb_gadget_class = NULL;
                return status;
        }

        major = MAJOR(devt);
        minors = count;

        return status;
}

static void gprinter_cleanup(void)
{
        if (major) {
                unregister_chrdev_region(MKDEV(major, 0), minors);
                major = minors = 0;
        }
        class_destroy(usb_gadget_class);
        usb_gadget_class = NULL;
}