// SPDX-License-Identifier: GPL-2.0+
/*
 * mass_storage.c -- Mass Storage USB Gadget
 *
 * Copyright (C) 2003-2008 Alan Stern
 * Copyright (C) 2009 Samsung Electronics
 *                    Author: Michal Nazarewicz <mina86@mina86.com>
 * All rights reserved.
 */


/*
 * The Mass Storage Gadget acts as a USB Mass Storage device,
 * appearing to the host as a disk drive or as a CD-ROM drive.  In
 * addition to providing an example of a genuinely useful gadget
 * driver for a USB device, it also illustrates a technique of
 * double-buffering for increased throughput.  Last but not least, it
 * gives an easy way to probe the behavior of the Mass Storage drivers
 * in a USB host.
 *
 * Since this file serves only administrative purposes and all the
 * business logic is implemented in f_mass_storage.* file.  Read
 * comments in this file for more detailed description.
 */


#include <linux/kernel.h>
#include <linux/usb/ch9.h>
#include <linux/module.h>

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

#define DRIVER_DESC             "Mass Storage Gadget"
#define DRIVER_VERSION          "2009/09/11"

/*
 * Thanks to NetChip Technologies for donating this product ID.
 *
 * DO NOT REUSE THESE IDs with any other driver!!  Ever!!
 * Instead:  allocate your own, using normal USB-IF procedures.
 */
#define FSG_VENDOR_ID   0x0525  /* NetChip */
#define FSG_PRODUCT_ID  0xa4a5  /* Linux-USB File-backed Storage Gadget */

#include "f_mass_storage.h"

/*-------------------------------------------------------------------------*/
USB_GADGET_COMPOSITE_OPTIONS();

static struct usb_device_descriptor msg_device_desc = {
        .bLength =              sizeof msg_device_desc,
        .bDescriptorType =      USB_DT_DEVICE,

        /* .bcdUSB = DYNAMIC */
        .bDeviceClass =         USB_CLASS_PER_INTERFACE,

        /* Vendor and product id can be overridden by module parameters.  */
        .idVendor =             cpu_to_le16(FSG_VENDOR_ID),
        .idProduct =            cpu_to_le16(FSG_PRODUCT_ID),
        .bNumConfigurations =   1,
};

static const struct usb_descriptor_header *otg_desc[2];

static struct usb_string strings_dev[] = {
        [USB_GADGET_MANUFACTURER_IDX].s = "",
        [USB_GADGET_PRODUCT_IDX].s = DRIVER_DESC,
        [USB_GADGET_SERIAL_IDX].s = "",
        {  } /* end of list */
};

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

static struct usb_gadget_strings *dev_strings[] = {
        &stringtab_dev,
        NULL,
};

static struct usb_function_instance *fi_msg;
static struct usb_function *f_msg;

/****************************** Configurations ******************************/

static struct fsg_module_parameters mod_data = {
        .stall = 1
};
#ifdef CONFIG_USB_GADGET_DEBUG_FILES

static unsigned int fsg_num_buffers = CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS;

#else

/*
 * Number of buffers we will use.
 * 2 is usually enough for good buffering pipeline
 */
#define fsg_num_buffers CONFIG_USB_GADGET_STORAGE_NUM_BUFFERS

#endif /* CONFIG_USB_GADGET_DEBUG_FILES */

FSG_MODULE_PARAMETERS(/* no prefix */, mod_data);

static int msg_do_config(struct usb_configuration *c)
{
        struct fsg_opts *opts;
        int ret;

        if (gadget_is_otg(c->cdev->gadget)) {
                c->descriptors = otg_desc;
                c->bmAttributes |= USB_CONFIG_ATT_WAKEUP;
        }

        opts = fsg_opts_from_func_inst(fi_msg);

        f_msg = usb_get_function(fi_msg);
        if (IS_ERR(f_msg))
                return PTR_ERR(f_msg);

        ret = usb_add_function(c, f_msg);
        if (ret)
                goto put_func;

        return 0;

put_func:
        usb_put_function(f_msg);
        return ret;
}

static struct usb_configuration msg_config_driver = {
        .label                  = "Linux File-Backed Storage",
        .bConfigurationValue    = 1,
        .bmAttributes           = USB_CONFIG_ATT_SELFPOWER,
};


/****************************** Gadget Bind ******************************/

static int msg_bind(struct usb_composite_dev *cdev)
{
        struct fsg_opts *opts;
        struct fsg_config config;
        int status;

        fi_msg = usb_get_function_instance("mass_storage");
        if (IS_ERR(fi_msg))
                return PTR_ERR(fi_msg);

        fsg_config_from_params(&config, &mod_data, fsg_num_buffers);
        opts = fsg_opts_from_func_inst(fi_msg);

        opts->no_configfs = true;
        status = fsg_common_set_num_buffers(opts->common, fsg_num_buffers);
        if (status)
                goto fail;

        status = fsg_common_set_cdev(opts->common, cdev, config.can_stall);
        if (status)
                goto fail_set_cdev;

        fsg_common_set_sysfs(opts->common, true);
        status = fsg_common_create_luns(opts->common, &config);
        if (status)
                goto fail_set_cdev;

        fsg_common_set_inquiry_string(opts->common, config.vendor_name,
                                      config.product_name);

        status = usb_string_ids_tab(cdev, strings_dev);
        if (status < 0)
                goto fail_string_ids;
        msg_device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;

        if (gadget_is_otg(cdev->gadget) && !otg_desc[0]) {
                struct usb_descriptor_header *usb_desc;

                usb_desc = usb_otg_descriptor_alloc(cdev->gadget);
                if (!usb_desc)
                        goto fail_string_ids;
                usb_otg_descriptor_init(cdev->gadget, usb_desc);
                otg_desc[0] = usb_desc;
                otg_desc[1] = NULL;
        }

        status = usb_add_config(cdev, &msg_config_driver, msg_do_config);
        if (status < 0)
                goto fail_otg_desc;

        usb_composite_overwrite_options(cdev, &coverwrite);
        dev_info(&cdev->gadget->dev,
                 DRIVER_DESC ", version: " DRIVER_VERSION "\n");
        return 0;

fail_otg_desc:
        kfree(otg_desc[0]);
        otg_desc[0] = NULL;
fail_string_ids:
        fsg_common_remove_luns(opts->common);
fail_set_cdev:
        fsg_common_free_buffers(opts->common);
fail:
        usb_put_function_instance(fi_msg);
        return status;
}

static int msg_unbind(struct usb_composite_dev *cdev)
{
        if (!IS_ERR(f_msg))
                usb_put_function(f_msg);

        if (!IS_ERR(fi_msg))
                usb_put_function_instance(fi_msg);

        kfree(otg_desc[0]);
        otg_desc[0] = NULL;

        return 0;
}

/****************************** Some noise ******************************/

static struct usb_composite_driver msg_driver = {
        .name           = "g_mass_storage",
        .dev            = &msg_device_desc,
        .max_speed      = USB_SPEED_SUPER_PLUS,
        .needs_serial   = 1,
        .strings        = dev_strings,
        .bind           = msg_bind,
        .unbind         = msg_unbind,
};

MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_AUTHOR("Michal Nazarewicz");
MODULE_LICENSE("GPL");

static int __init msg_init(void)
{
        return usb_composite_probe(&msg_driver);
}
module_init(msg_init);

static void __exit msg_cleanup(void)
{
        usb_composite_unregister(&msg_driver);
}
module_exit(msg_cleanup);