// SPDX-License-Identifier: GPL-2.0+
/*
 * f_loopback.c - USB peripheral loopback configuration driver
 *
 * Copyright (C) 2003-2008 David Brownell
 * Copyright (C) 2008 by Nokia Corporation
 */

/* #define VERBOSE_DEBUG */

#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/err.h>
#include <linux/usb/composite.h>
#include <linux/usb/func_utils.h>

#include "g_zero.h"

/*
 * LOOPBACK FUNCTION ... a testing vehicle for USB peripherals,
 *
 * This takes messages of various sizes written OUT to a device, and loops
 * them back so they can be read IN from it.  It has been used by certain
 * test applications.  It supports limited testing of data queueing logic.
 */
struct f_loopback {
        struct usb_function     function;

        struct usb_ep           *in_ep;
        struct usb_ep           *out_ep;

        unsigned                qlen;
        unsigned                buflen;
};

static inline struct f_loopback *func_to_loop(struct usb_function *f)
{
        return container_of(f, struct f_loopback, function);
}

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

static struct usb_interface_descriptor loopback_intf = {
        .bLength =              sizeof(loopback_intf),
        .bDescriptorType =      USB_DT_INTERFACE,

        .bNumEndpoints =        2,
        .bInterfaceClass =      USB_CLASS_VENDOR_SPEC,
        /* .iInterface = DYNAMIC */
};

/* full speed support: */

static struct usb_endpoint_descriptor fs_loop_source_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_loop_sink_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_loopback_descs[] = {
        (struct usb_descriptor_header *) &loopback_intf,
        (struct usb_descriptor_header *) &fs_loop_sink_desc,
        (struct usb_descriptor_header *) &fs_loop_source_desc,
        NULL,
};

/* high speed support: */

static struct usb_endpoint_descriptor hs_loop_source_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_loop_sink_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_loopback_descs[] = {
        (struct usb_descriptor_header *) &loopback_intf,
        (struct usb_descriptor_header *) &hs_loop_source_desc,
        (struct usb_descriptor_header *) &hs_loop_sink_desc,
        NULL,
};

/* super speed support: */

static struct usb_endpoint_descriptor ss_loop_source_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_loop_source_comp_desc = {
        .bLength =              USB_DT_SS_EP_COMP_SIZE,
        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
        .bMaxBurst =            0,
        .bmAttributes =         0,
        .wBytesPerInterval =    0,
};

static struct usb_endpoint_descriptor ss_loop_sink_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_loop_sink_comp_desc = {
        .bLength =              USB_DT_SS_EP_COMP_SIZE,
        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
        .bMaxBurst =            0,
        .bmAttributes =         0,
        .wBytesPerInterval =    0,
};

static struct usb_descriptor_header *ss_loopback_descs[] = {
        (struct usb_descriptor_header *) &loopback_intf,
        (struct usb_descriptor_header *) &ss_loop_source_desc,
        (struct usb_descriptor_header *) &ss_loop_source_comp_desc,
        (struct usb_descriptor_header *) &ss_loop_sink_desc,
        (struct usb_descriptor_header *) &ss_loop_sink_comp_desc,
        NULL,
};

/* function-specific strings: */

static struct usb_string strings_loopback[] = {
        [0].s = "loop input to output",
        {  }                    /* end of list */
};

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

static struct usb_gadget_strings *loopback_strings[] = {
        &stringtab_loop,
        NULL,
};

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

static int loopback_bind(struct usb_configuration *c, struct usb_function *f)
{
        struct usb_composite_dev *cdev = c->cdev;
        struct f_loopback       *loop = func_to_loop(f);
        int                     id;
        int ret;

        /* allocate interface ID(s) */
        id = usb_interface_id(c, f);
        if (id < 0)
                return id;
        loopback_intf.bInterfaceNumber = id;

        id = usb_string_id(cdev);
        if (id < 0)
                return id;
        strings_loopback[0].id = id;
        loopback_intf.iInterface = id;

        /* allocate endpoints */

        loop->in_ep = usb_ep_autoconfig(cdev->gadget, &fs_loop_source_desc);
        if (!loop->in_ep) {
autoconf_fail:
                ERROR(cdev, "%s: can't autoconfigure on %s\n",
                        f->name, cdev->gadget->name);
                return -ENODEV;
        }

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

        /* support high speed hardware */
        hs_loop_source_desc.bEndpointAddress =
                fs_loop_source_desc.bEndpointAddress;
        hs_loop_sink_desc.bEndpointAddress = fs_loop_sink_desc.bEndpointAddress;

        /* support super speed hardware */
        ss_loop_source_desc.bEndpointAddress =
                fs_loop_source_desc.bEndpointAddress;
        ss_loop_sink_desc.bEndpointAddress = fs_loop_sink_desc.bEndpointAddress;

        ret = usb_assign_descriptors(f, fs_loopback_descs, hs_loopback_descs,
                        ss_loopback_descs, ss_loopback_descs);
        if (ret)
                return ret;

        DBG(cdev, "%s: IN/%s, OUT/%s\n",
                        f->name, loop->in_ep->name, loop->out_ep->name);
        return 0;
}

static void lb_free_func(struct usb_function *f)
{
        struct f_lb_opts *opts;

        opts = container_of(f->fi, struct f_lb_opts, func_inst);

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

        usb_free_all_descriptors(f);
        kfree(func_to_loop(f));
}

static void loopback_complete(struct usb_ep *ep, struct usb_request *req)
{
        struct f_loopback       *loop = ep->driver_data;
        struct usb_composite_dev *cdev = loop->function.config->cdev;
        int                     status = req->status;

        switch (status) {
        case 0:                         /* normal completion? */
                if (ep == loop->out_ep) {
                        /*
                         * We received some data from the host so let's
                         * queue it so host can read the from our in ep
                         */
                        struct usb_request *in_req = req->context;

                        in_req->zero = (req->actual < req->length);
                        in_req->length = req->actual;
                        ep = loop->in_ep;
                        req = in_req;
                } else {
                        /*
                         * We have just looped back a bunch of data
                         * to host. Now let's wait for some more data.
                         */
                        req = req->context;
                        ep = loop->out_ep;
                }

                /* queue the buffer back to host or for next bunch of data */
                status = usb_ep_queue(ep, req, GFP_ATOMIC);
                if (status == 0) {
                        return;
                } else {
                        ERROR(cdev, "Unable to loop back buffer to %s: %d\n",
                              ep->name, status);
                        goto free_req;
                }

                /* "should never get here" */
        default:
                ERROR(cdev, "%s loop complete --> %d, %d/%d\n", ep->name,
                                status, req->actual, req->length);
                fallthrough;

        /* NOTE:  since this driver doesn't maintain an explicit record
         * of requests it submitted (just maintains qlen count), we
         * rely on the hardware driver to clean up on disconnect or
         * endpoint disable.
         */
        case -ECONNABORTED:             /* hardware forced ep reset */
        case -ECONNRESET:               /* request dequeued */
        case -ESHUTDOWN:                /* disconnect from host */
free_req:
                usb_ep_free_request(ep == loop->in_ep ?
                                    loop->out_ep : loop->in_ep,
                                    req->context);
                free_ep_req(ep, req);
                return;
        }
}

static void disable_loopback(struct f_loopback *loop)
{
        struct usb_composite_dev        *cdev;

        cdev = loop->function.config->cdev;
        disable_endpoints(cdev, loop->in_ep, loop->out_ep, NULL, NULL);
        VDBG(cdev, "%s disabled\n", loop->function.name);
}

static inline struct usb_request *lb_alloc_ep_req(struct usb_ep *ep, int len)
{
        return alloc_ep_req(ep, len);
}

static int alloc_requests(struct usb_composite_dev *cdev,
                          struct f_loopback *loop)
{
        struct usb_request *in_req, *out_req;
        int i;
        int result = 0;

        /*
         * allocate a bunch of read buffers and queue them all at once.
         * we buffer at most 'qlen' transfers; We allocate buffers only
         * for out transfer and reuse them in IN transfers to implement
         * our loopback functionality
         */
        for (i = 0; i < loop->qlen && result == 0; i++) {
                result = -ENOMEM;

                in_req = usb_ep_alloc_request(loop->in_ep, GFP_ATOMIC);
                if (!in_req)
                        goto fail;

                out_req = lb_alloc_ep_req(loop->out_ep, loop->buflen);
                if (!out_req)
                        goto fail_in;

                in_req->complete = loopback_complete;
                out_req->complete = loopback_complete;

                in_req->buf = out_req->buf;
                /* length will be set in complete routine */
                in_req->context = out_req;
                out_req->context = in_req;

                result = usb_ep_queue(loop->out_ep, out_req, GFP_ATOMIC);
                if (result) {
                        ERROR(cdev, "%s queue req --> %d\n",
                                        loop->out_ep->name, result);
                        goto fail_out;
                }
        }

        return 0;

fail_out:
        free_ep_req(loop->out_ep, out_req);
fail_in:
        usb_ep_free_request(loop->in_ep, in_req);
fail:
        return result;
}

static int enable_endpoint(struct usb_composite_dev *cdev,
                           struct f_loopback *loop, struct usb_ep *ep)
{
        int                                     result;

        result = config_ep_by_speed(cdev->gadget, &(loop->function), ep);
        if (result)
                goto out;

        result = usb_ep_enable(ep);
        if (result < 0)
                goto out;
        ep->driver_data = loop;
        result = 0;

out:
        return result;
}

static int
enable_loopback(struct usb_composite_dev *cdev, struct f_loopback *loop)
{
        int                                     result = 0;

        result = enable_endpoint(cdev, loop, loop->in_ep);
        if (result)
                goto out;

        result = enable_endpoint(cdev, loop, loop->out_ep);
        if (result)
                goto disable_in;

        result = alloc_requests(cdev, loop);
        if (result)
                goto disable_out;

        DBG(cdev, "%s enabled\n", loop->function.name);
        return 0;

disable_out:
        usb_ep_disable(loop->out_ep);
disable_in:
        usb_ep_disable(loop->in_ep);
out:
        return result;
}

static int loopback_set_alt(struct usb_function *f,
                unsigned intf, unsigned alt)
{
        struct f_loopback       *loop = func_to_loop(f);
        struct usb_composite_dev *cdev = f->config->cdev;

        /* we know alt is zero */
        disable_loopback(loop);
        return enable_loopback(cdev, loop);
}

static void loopback_disable(struct usb_function *f)
{
        struct f_loopback       *loop = func_to_loop(f);

        disable_loopback(loop);
}

static struct usb_function *loopback_alloc(struct usb_function_instance *fi)
{
        struct f_loopback       *loop;
        struct f_lb_opts        *lb_opts;

        loop = kzalloc_obj(*loop);
        if (!loop)
                return ERR_PTR(-ENOMEM);

        lb_opts = container_of(fi, struct f_lb_opts, func_inst);

        mutex_lock(&lb_opts->lock);
        lb_opts->refcnt++;
        mutex_unlock(&lb_opts->lock);

        loop->buflen = lb_opts->bulk_buflen;
        loop->qlen = lb_opts->qlen;
        if (!loop->qlen)
                loop->qlen = 32;

        loop->function.name = "loopback";
        loop->function.bind = loopback_bind;
        loop->function.set_alt = loopback_set_alt;
        loop->function.disable = loopback_disable;
        loop->function.strings = loopback_strings;

        loop->function.free_func = lb_free_func;

        return &loop->function;
}

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

static void lb_attr_release(struct config_item *item)
{
        struct f_lb_opts *lb_opts = to_f_lb_opts(item);

        usb_put_function_instance(&lb_opts->func_inst);
}

static const struct configfs_item_operations lb_item_ops = {
        .release                = lb_attr_release,
};

static ssize_t f_lb_opts_qlen_show(struct config_item *item, char *page)
{
        struct f_lb_opts *opts = to_f_lb_opts(item);
        int result;

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

        return result;
}

static ssize_t f_lb_opts_qlen_store(struct config_item *item,
                                    const char *page, size_t len)
{
        struct f_lb_opts *opts = to_f_lb_opts(item);
        int ret;
        u32 num;

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

        ret = kstrtou32(page, 0, &num);
        if (ret)
                goto end;

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

CONFIGFS_ATTR(f_lb_opts_, qlen);

static ssize_t f_lb_opts_bulk_buflen_show(struct config_item *item, char *page)
{
        struct f_lb_opts *opts = to_f_lb_opts(item);
        int result;

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

        return result;
}

static ssize_t f_lb_opts_bulk_buflen_store(struct config_item *item,
                                    const char *page, size_t len)
{
        struct f_lb_opts *opts = to_f_lb_opts(item);
        int ret;
        u32 num;

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

        ret = kstrtou32(page, 0, &num);
        if (ret)
                goto end;

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

CONFIGFS_ATTR(f_lb_opts_, bulk_buflen);

static struct configfs_attribute *lb_attrs[] = {
        &f_lb_opts_attr_qlen,
        &f_lb_opts_attr_bulk_buflen,
        NULL,
};

static const struct config_item_type lb_func_type = {
        .ct_item_ops    = &lb_item_ops,
        .ct_attrs       = lb_attrs,
        .ct_owner       = THIS_MODULE,
};

static void lb_free_instance(struct usb_function_instance *fi)
{
        struct f_lb_opts *lb_opts;

        lb_opts = container_of(fi, struct f_lb_opts, func_inst);
        kfree(lb_opts);
}

static struct usb_function_instance *loopback_alloc_instance(void)
{
        struct f_lb_opts *lb_opts;

        lb_opts = kzalloc_obj(*lb_opts);
        if (!lb_opts)
                return ERR_PTR(-ENOMEM);
        mutex_init(&lb_opts->lock);
        lb_opts->func_inst.free_func_inst = lb_free_instance;
        lb_opts->bulk_buflen = GZERO_BULK_BUFLEN;
        lb_opts->qlen = GZERO_QLEN;

        config_group_init_type_name(&lb_opts->func_inst.group, "",
                                    &lb_func_type);

        return  &lb_opts->func_inst;
}
DECLARE_USB_FUNCTION(Loopback, loopback_alloc_instance, loopback_alloc);

int __init lb_modinit(void)
{
        return usb_function_register(&Loopbackusb_func);
}

void __exit lb_modexit(void)
{
        usb_function_unregister(&Loopbackusb_func);
}

MODULE_DESCRIPTION("USB peripheral loopback configuration driver");
MODULE_LICENSE("GPL");