/*
 * f_loopback.c - USB peripheral loopback configuration driver
 *
 * Copyright (C) 2003-2008 David Brownell
 * Copyright (C) 2008 by Nokia Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/* #define VERBOSE_DEBUG */

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

#include "g_zero.h"
#include "gadget_chips.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.
 *
 *
 * This is currently packaged as a configuration driver, which can't be
 * combined with other functions to make composite devices.  However, it
 * can be combined with other independent configurations.
 */
struct f_loopback {
        struct usb_function     function;

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

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

static unsigned qlen = 32;
module_param(qlen, uint, 0);
MODULE_PARM_DESC(qlenn, "depth of loopback queue");

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

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,
};

/* 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 __init
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;

        /* allocate interface ID(s) */
        id = usb_interface_id(c, f);
        if (id < 0)
                return id;
        loopback_intf.bInterfaceNumber = 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->in_ep->driver_data = cdev;        /* claim */

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

        /* support high speed hardware */
        if (gadget_is_dualspeed(c->cdev->gadget)) {
                hs_loop_source_desc.bEndpointAddress =
                                fs_loop_source_desc.bEndpointAddress;
                hs_loop_sink_desc.bEndpointAddress =
                                fs_loop_sink_desc.bEndpointAddress;
                f->hs_descriptors = hs_loopback_descs;
        }

        DBG(cdev, "%s speed %s: IN/%s, OUT/%s\n",
                        gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
                        f->name, loop->in_ep->name, loop->out_ep->name);
        return 0;
}

static void
loopback_unbind(struct usb_configuration *c, struct usb_function *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) {
                        /* loop this OUT packet back IN to the host */
                        req->zero = (req->actual < req->length);
                        req->length = req->actual;
                        status = usb_ep_queue(loop->in_ep, req, GFP_ATOMIC);
                        if (status == 0)
                                return;

                        /* "should never get here" */
                        ERROR(cdev, "can't loop %s to %s: %d\n",
                                ep->name, loop->in_ep->name,
                                status);
                }

                /* queue the buffer for some later OUT packet */
                req->length = buflen;
                status = usb_ep_queue(loop->out_ep, req, GFP_ATOMIC);
                if (status == 0)
                        return;

                /* "should never get here" */
                /* FALLTHROUGH */

        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_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);
        VDBG(cdev, "%s disabled\n", loop->function.name);
}

static int
enable_loopback(struct usb_composite_dev *cdev, struct f_loopback *loop)
{
        int                                     result = 0;
        const struct usb_endpoint_descriptor    *src, *sink;
        struct usb_ep                           *ep;
        struct usb_request                      *req;
        unsigned                                i;

        src = ep_choose(cdev->gadget,
                        &hs_loop_source_desc, &fs_loop_source_desc);
        sink = ep_choose(cdev->gadget,
                        &hs_loop_sink_desc, &fs_loop_sink_desc);

        /* one endpoint writes data back IN to the host */
        ep = loop->in_ep;
        result = usb_ep_enable(ep, src);
        if (result < 0)
                return result;
        ep->driver_data = loop;

        /* one endpoint just reads OUT packets */
        ep = loop->out_ep;
        result = usb_ep_enable(ep, sink);
        if (result < 0) {
fail0:
                ep = loop->in_ep;
                usb_ep_disable(ep);
                ep->driver_data = NULL;
                return result;
        }
        ep->driver_data = loop;

        /* allocate a bunch of read buffers and queue them all at once.
         * we buffer at most 'qlen' transfers; fewer if any need more
         * than 'buflen' bytes each.
         */
        for (i = 0; i < qlen && result == 0; i++) {
                req = alloc_ep_req(ep);
                if (req) {
                        req->complete = loopback_complete;
                        result = usb_ep_queue(ep, req, GFP_ATOMIC);
                        if (result)
                                ERROR(cdev, "%s queue req --> %d\n",
                                                ep->name, result);
                } else {
                        usb_ep_disable(ep);
                        ep->driver_data = NULL;
                        result = -ENOMEM;
                        goto fail0;
                }
        }

        DBG(cdev, "%s enabled\n", loop->function.name);
        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 */
        if (loop->in_ep->driver_data)
                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 int __init loopback_bind_config(struct usb_configuration *c)
{
        struct f_loopback       *loop;
        int                     status;

        loop = kzalloc(sizeof *loop, GFP_KERNEL);
        if (!loop)
                return -ENOMEM;

        loop->function.name = "loopback";
        loop->function.descriptors = fs_loopback_descs;
        loop->function.bind = loopback_bind;
        loop->function.unbind = loopback_unbind;
        loop->function.set_alt = loopback_set_alt;
        loop->function.disable = loopback_disable;

        status = usb_add_function(c, &loop->function);
        if (status)
                kfree(loop);
        return status;
}

static struct usb_configuration loopback_driver = {
        .label          = "loopback",
        .strings        = loopback_strings,
        .bind           = loopback_bind_config,
        .bConfigurationValue = 2,
        .bmAttributes   = USB_CONFIG_ATT_SELFPOWER,
        /* .iConfiguration = DYNAMIC */
};

/**
 * loopback_add - add a loopback testing configuration to a device
 * @cdev: the device to support the loopback configuration
 */
int __init loopback_add(struct usb_composite_dev *cdev, bool autoresume)
{
        int id;

        /* allocate string ID(s) */
        id = usb_string_id(cdev);
        if (id < 0)
                return id;
        strings_loopback[0].id = id;

        loopback_intf.iInterface = id;
        loopback_driver.iConfiguration = id;

        /* support autoresume for remote wakeup testing */
        if (autoresume)
                sourcesink_driver.bmAttributes |= USB_CONFIG_ATT_WAKEUP;

        /* support OTG systems */
        if (gadget_is_otg(cdev->gadget)) {
                loopback_driver.descriptors = otg_desc;
                loopback_driver.bmAttributes |= USB_CONFIG_ATT_WAKEUP;
        }

        return usb_add_config(cdev, &loopback_driver);
}