usbblk.c

Go to the documentation of this file.

/*
 * Copyright (C) 2020 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <ipxe/usb.h>
#include <ipxe/scsi.h>
#include <ipxe/xfer.h>
#include <ipxe/uri.h>
#include <ipxe/open.h>
#include <ipxe/efi/efi_path.h>
#include "usbblk.h"

/** @file
 *
 * USB mass storage driver
 *
 */

static void usbblk_stop ( struct usbblk_device *usbblk, int rc );

/** List of USB block devices */
static LIST_HEAD ( usbblk_devices );

/******************************************************************************
 *
 * Endpoint management
 *
 ******************************************************************************
 */

/**
 * Open endpoints
 *
 * @v usbblk            USB block device
 * @ret rc              Return status code
 */
static int usbblk_open ( struct usbblk_device *usbblk ) {
        struct usb_device *usb = usbblk->func->usb;
        unsigned int interface = usbblk->func->interface[0];
        int rc;

        /* Sanity checks */
        assert ( ! usbblk->in.open );
        assert ( ! usbblk->out.open );

        /* Issue reset */
        if ( ( rc = usb_control ( usb, USBBLK_RESET, 0, interface,
                                  NULL, 0 ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not issue reset: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_reset;
        }

        /* Open bulk OUT endpoint */
        if ( ( rc = usb_endpoint_open ( &usbblk->out ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not open bulk OUT: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_open_out;
        }

        /* Clear any bulk OUT halt condition */
        if ( ( rc = usb_endpoint_clear_halt ( &usbblk->out ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not reset bulk OUT: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_clear_out;
        }

        /* Open bulk IN endpoint */
        if ( ( rc = usb_endpoint_open ( &usbblk->in ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not open bulk IN: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_open_in;
        }

        /* Clear any bulk IN halt condition */
        if ( ( rc = usb_endpoint_clear_halt ( &usbblk->in ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not reset bulk IN: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_clear_in;
        }

        return 0;

 err_clear_in:
        usb_endpoint_close ( &usbblk->in );
 err_open_in:
 err_clear_out:
        usb_endpoint_close ( &usbblk->out );
 err_open_out:
 err_reset:
        return rc;
}

/**
 * Close endpoints
 *
 * @v usbblk            USB block device
 */
static void usbblk_close ( struct usbblk_device *usbblk ) {

        /* Close bulk OUT endpoint */
        if ( usbblk->out.open )
                usb_endpoint_close ( &usbblk->out );

        /* Close bulk IN endpoint */
        if ( usbblk->in.open )
                usb_endpoint_close ( &usbblk->in );
}

/******************************************************************************
 *
 * Bulk OUT endpoint
 *
 ******************************************************************************
 */

/**
 * Issue bulk OUT command
 *
 * @v usbblk            USB block device
 * @ret rc              Return status code
 */
static int usbblk_out_command ( struct usbblk_device *usbblk ) {
        struct usbblk_command *cmd = &usbblk->cmd;
        struct usbblk_command_wrapper *wrapper;
        struct io_buffer *iobuf;
        int rc;

        /* Sanity checks */
        assert ( cmd->tag );
        assert ( ! ( cmd->scsi.data_in_len && cmd->scsi.data_out_len ) );

        /* Allocate I/O buffer */
        iobuf = alloc_iob ( sizeof ( *wrapper ) );
        if ( ! iobuf ) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        /* Populate command */
        wrapper = iob_put ( iobuf, sizeof ( *wrapper ) );
        memset ( wrapper, 0, sizeof ( *wrapper ) );
        wrapper->signature = cpu_to_le32 ( USBBLK_COMMAND_SIGNATURE );
        wrapper->tag = cmd->tag; /* non-endian */
        if ( cmd->scsi.data_out_len ) {
                wrapper->len = cpu_to_le32 ( cmd->scsi.data_out_len );
        } else {
                wrapper->len = cpu_to_le32 ( cmd->scsi.data_in_len );
                wrapper->flags = USB_DIR_IN;
        }
        wrapper->lun = ntohs ( cmd->scsi.lun.u16[0] );
        wrapper->cblen = sizeof ( wrapper->cb );
        memcpy ( wrapper->cb, &cmd->scsi.cdb, sizeof ( wrapper->cb ) );

        /* Issue command */
        if ( ( rc = usb_stream ( &usbblk->out, iobuf, 0 ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s bulk OUT could not issue command: "
                       "%s\n", usbblk->func->name, strerror ( rc ) );
                goto err_stream;
        }

        return 0;

 err_stream:
        free_iob ( iobuf );
 err_alloc:
        return rc;
}

/**
 * Send bulk OUT data block
 *
 * @v usbblk            USB block device
 * @ret rc              Return status code
 */
static int usbblk_out_data ( struct usbblk_device *usbblk ) {
        struct usbblk_command *cmd = &usbblk->cmd;
        struct io_buffer *iobuf;
        size_t len;
        int rc;

        /* Calculate length */
        assert ( cmd->tag );
        assert ( cmd->scsi.data_out != NULL );
        assert ( cmd->offset < cmd->scsi.data_out_len );
        len = ( cmd->scsi.data_out_len - cmd->offset );
        if ( len > USBBLK_MAX_LEN )
                len = USBBLK_MAX_LEN;
        assert ( ( len % usbblk->out.mtu ) == 0 );

        /* Allocate I/O buffer */
        iobuf = alloc_iob ( len );
        if ( ! iobuf ) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        /* Populate I/O buffer */
        memcpy ( iob_put ( iobuf, len ),
                 ( cmd->scsi.data_out + cmd->offset ), len );

        /* Send data */
        if ( ( rc = usb_stream ( &usbblk->out, iobuf, 0 ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s bulk OUT could not send data: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_stream;
        }

        /* Consume data */
        cmd->offset += len;

        return 0;

 err_stream:
        free_iob ( iobuf );
 err_alloc:
        return rc;
}

/**
 * Refill bulk OUT endpoint
 *
 * @v usbblk            USB block device
 * @ret rc              Return status code
 */
static int usbblk_out_refill ( struct usbblk_device *usbblk ) {
        struct usbblk_command *cmd = &usbblk->cmd;
        int rc;

        /* Sanity checks */
        assert ( cmd->tag );

        /* Refill endpoint */
        while ( ( cmd->offset < cmd->scsi.data_out_len ) &&
                ( usbblk->out.fill < USBBLK_MAX_FILL ) ) {
                if ( ( rc = usbblk_out_data ( usbblk ) ) != 0 )
                        return rc;
        }

        return 0;
}

/**
 * Complete bulk OUT transfer
 *
 * @v ep                USB endpoint
 * @v iobuf             I/O buffer
 * @v rc                Completion status code
 */
static void usbblk_out_complete ( struct usb_endpoint *ep,
                                  struct io_buffer *iobuf, int rc ) {
        struct usbblk_device *usbblk =
                container_of ( ep, struct usbblk_device, out );
        struct usbblk_command *cmd = &usbblk->cmd;

        /* Ignore cancellations after closing endpoint */
        if ( ! ep->open )
                goto drop;

        /* Sanity check */
        assert ( cmd->tag );

        /* Check for failures */
        if ( rc != 0 ) {
                DBGC ( usbblk, "USBBLK %s bulk OUT failed: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err;
        }

        /* Trigger refill process, if applicable */
        if ( cmd->offset < cmd->scsi.data_out_len )
                process_add ( &usbblk->process );

 drop:
        /* Free I/O buffer */
        free_iob ( iobuf );

        return;

 err:
        free_iob ( iobuf );
        usbblk_stop ( usbblk, rc );
}

/** Bulk OUT endpoint operations */
static struct usb_endpoint_driver_operations usbblk_out_operations = {
        .complete = usbblk_out_complete,
};

/******************************************************************************
 *
 * Bulk IN endpoint
 *
 ******************************************************************************
 */

/**
 * Handle bulk IN data block
 *
 * @v usbblk            USB block device
 * @v data              Data block
 * @v len               Length of data
 * @ret rc              Return status code
 */
static int usbblk_in_data ( struct usbblk_device *usbblk, const void *data,
                            size_t len ) {
        struct usbblk_command *cmd = &usbblk->cmd;

        /* Sanity checks */
        assert ( cmd->tag );
        assert ( cmd->scsi.data_in != NULL );
        assert ( cmd->offset <= cmd->scsi.data_in_len );
        assert ( len <= ( cmd->scsi.data_in_len - cmd->offset ) );

        /* Store data */
        memcpy ( ( cmd->scsi.data_in + cmd->offset ), data, len );
        cmd->offset += len;

        return 0;
}

/**
 * Handle bulk IN status
 *
 * @v usbblk            USB block device
 * @v data              Status data
 * @v len               Length of status data
 * @ret rc              Return status code
 */
static int usbblk_in_status ( struct usbblk_device *usbblk, const void *data,
                              size_t len ) {
        struct usbblk_command *cmd = &usbblk->cmd;
        const struct usbblk_status_wrapper *stat;

        /* Sanity checks */
        assert ( cmd->tag );

        /* Validate length */
        if ( len < sizeof ( *stat ) ) {
                DBGC ( usbblk, "USBBLK %s bulk IN malformed status:\n",
                       usbblk->func->name );
                DBGC_HDA ( usbblk, 0, data, len );
                return -EIO;
        }
        stat = data;

        /* Validate signature */
        if ( stat->signature != cpu_to_le32 ( USBBLK_STATUS_SIGNATURE ) ) {
                DBGC ( usbblk, "USBBLK %s bulk IN invalid signature %08x:\n",
                       usbblk->func->name, le32_to_cpu ( stat->signature ) );
                DBGC_HDA ( usbblk, 0, stat, sizeof ( *stat ) );
                return -EIO;
        }

        /* Validate tag */
        if ( stat->tag != cmd->tag ) {
                DBGC ( usbblk, "USBBLK %s bulk IN tag mismatch (got %08x, "
                       "expected %08x):\n",
                       usbblk->func->name, stat->tag, cmd->tag );
                DBGC_HDA ( usbblk, 0, stat, sizeof ( *stat ) );
                return -EIO;
        }

        /* Check status */
        if ( stat->status ) {
                DBGC ( usbblk, "USBBLK %s bulk IN status %02x:\n",
                       usbblk->func->name, stat->status );
                DBGC_HDA ( usbblk, 0, stat, sizeof ( *stat ) );
                return -EIO;
        }

        /* Check for residual data */
        if ( stat->residue ) {
                DBGC ( usbblk, "USBBLK %s bulk IN residue %#x:\n",
                       usbblk->func->name, le32_to_cpu ( stat->residue ) );
                return -EIO;
        }

        /* Mark command as complete */
        usbblk_stop ( usbblk, 0 );

        return 0;
}

/**
 * Refill bulk IN endpoint
 *
 * @v usbblk            USB block device
 * @ret rc              Return status code
 */
static int usbblk_in_refill ( struct usbblk_device *usbblk ) {
        struct usbblk_command *cmd = &usbblk->cmd;
        struct usbblk_status_wrapper *stat;
        size_t remaining;
        unsigned int max;
        int rc;

        /* Sanity checks */
        assert ( cmd->tag );

        /* Calculate maximum required refill */
        remaining = sizeof ( *stat );
        if ( cmd->scsi.data_in_len ) {
                assert ( cmd->offset <= cmd->scsi.data_in_len );
                remaining += ( cmd->scsi.data_in_len - cmd->offset );
        }
        max = ( ( remaining + USBBLK_MAX_LEN - 1 ) / USBBLK_MAX_LEN );

        /* Refill bulk IN endpoint */
        if ( ( rc = usb_refill_limit ( &usbblk->in, max ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Complete bulk IN transfer
 *
 * @v ep                USB endpoint
 * @v iobuf             I/O buffer
 * @v rc                Completion status code
 */
static void usbblk_in_complete ( struct usb_endpoint *ep,
                                 struct io_buffer *iobuf, int rc ) {
        struct usbblk_device *usbblk =
                container_of ( ep, struct usbblk_device, in );
        struct usbblk_command *cmd = &usbblk->cmd;
        size_t remaining;
        size_t len;

        /* Ignore cancellations after closing endpoint */
        if ( ! ep->open )
                goto drop;

        /* Sanity check */
        assert ( cmd->tag );

        /* Handle errors */
        if ( rc != 0 ) {
                DBGC ( usbblk, "USBBLK %s bulk IN failed: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err;
        }

        /* Trigger refill process */
        process_add ( &usbblk->process );

        /* Handle data portion, if any */
        if ( cmd->scsi.data_in_len ) {
                assert ( cmd->offset <= cmd->scsi.data_in_len );
                remaining = ( cmd->scsi.data_in_len - cmd->offset );
                len = iob_len ( iobuf );
                if ( len > remaining )
                        len = remaining;
                if ( len ) {
                        if ( ( rc = usbblk_in_data ( usbblk, iobuf->data,
                                                     len ) ) != 0 )
                                goto err;
                        iob_pull ( iobuf, len );
                }
        }

        /* Handle status portion, if any */
        len = iob_len ( iobuf );
        if ( len ) {
                if ( ( rc = usbblk_in_status ( usbblk, iobuf->data,
                                               len ) ) != 0 )
                        goto err;
        }

 drop:
        /* Free I/O buffer */
        free_iob ( iobuf );

        return;

 err:
        free_iob ( iobuf );
        usbblk_stop ( usbblk, rc );
}

/** Bulk IN endpoint operations */
static struct usb_endpoint_driver_operations usbblk_in_operations = {
        .complete = usbblk_in_complete,
};

/******************************************************************************
 *
 * Refill process
 *
 ******************************************************************************
 */

/**
 * Refill endpoints
 *
 * @v usbblk            USB block device
 */
static void usbblk_step ( struct usbblk_device *usbblk ) {

        /* Refill bulk OUT endpoint */
        usbblk_out_refill ( usbblk );

        /* Refill bulk IN endpoint */
        usbblk_in_refill ( usbblk );
}

/** Refill process descriptor */
static struct process_descriptor usbblk_process_desc =
        PROC_DESC ( struct usbblk_device, process, usbblk_step );

/******************************************************************************
 *
 * SCSI command management
 *
 ******************************************************************************
 */

/** Next command tag */
static uint16_t usbblk_tag;

/**
 * Stop SCSI command
 *
 * @v usbblk            USB block device
 * @v rc                Reason for stop
 */
static void usbblk_stop ( struct usbblk_device *usbblk, int rc ) {

        /* Stop process */
        process_del ( &usbblk->process );

        /* Reset command */
        memset ( &usbblk->cmd, 0, sizeof ( usbblk->cmd ) );

        /* Close endpoints if an error occurred */
        if ( rc != 0 ) {
                DBGC ( usbblk, "USBBLK %s closing for error recovery\n",
                       usbblk->func->name );
                usbblk_close ( usbblk );
        }

        /* Terminate command */
        intf_restart ( &usbblk->data, rc );
}

/**
 * Start new SCSI command
 *
 * @v usbblk            USB block device
 * @v scsicmd           SCSI command
 * @ret rc              Return status code
 */
static int usbblk_start ( struct usbblk_device *usbblk,
                          struct scsi_cmd *scsicmd ) {
        struct usbblk_command *cmd = &usbblk->cmd;
        int rc;

        /* Fail if command is in progress */
        if ( cmd->tag ) {
                rc = -EBUSY;
                DBGC ( usbblk, "USBBLK %s cannot support multiple commands\n",
                       usbblk->func->name );
                goto err_busy;
        }

        /* Refuse bidirectional commands */
        if ( scsicmd->data_in_len && scsicmd->data_out_len ) {
                rc = -EOPNOTSUPP;
                DBGC ( usbblk, "USBBLK %s cannot support bidirectional "
                       "commands\n", usbblk->func->name );
                goto err_bidirectional;
        }

        /* Sanity checks */
        assert ( ! process_running ( &usbblk->process ) );
        assert ( cmd->offset == 0 );

        /* Initialise command */
        memcpy ( &cmd->scsi, scsicmd, sizeof ( cmd->scsi ) );
        cmd->tag = ( USBBLK_TAG_MAGIC | ++usbblk_tag );

        /* Issue bulk OUT command */
        if ( ( rc = usbblk_out_command ( usbblk ) ) != 0 )
                goto err_command;

        /* Start refill process */
        process_add ( &usbblk->process );

        return 0;

 err_command:
        memset ( &usbblk->cmd, 0, sizeof ( usbblk->cmd ) );
 err_bidirectional:
 err_busy:
        return rc;
}

/******************************************************************************
 *
 * SCSI interfaces
 *
 ******************************************************************************
 */

/** SCSI data interface operations */
static struct interface_operation usbblk_data_operations[] = {
        INTF_OP ( intf_close, struct usbblk_device *, usbblk_stop ),
};

/** SCSI data interface descriptor */
static struct interface_descriptor usbblk_data_desc =
        INTF_DESC ( struct usbblk_device, data, usbblk_data_operations );

/**
 * Check SCSI command flow-control window
 *
 * @v usbblk            USB block device
 * @ret len             Length of window
 */
static size_t usbblk_scsi_window ( struct usbblk_device *usbblk ) {
        struct usbblk_command *cmd = &usbblk->cmd;

        /* Allow a single command if no command is currently in progress */
        return ( cmd->tag ? 0 : 1 );
}

/**
 * Issue SCSI command
 *
 * @v usbblk            USB block device
 * @v data              SCSI data interface
 * @v scsicmd           SCSI command
 * @ret tag             Command tag, or negative error
 */
static int usbblk_scsi_command ( struct usbblk_device *usbblk,
                                 struct interface *data,
                                 struct scsi_cmd *scsicmd ) {
        struct usbblk_command *cmd = &usbblk->cmd;
        int rc;

        /* (Re)open endpoints if needed */
        if ( ( ! usbblk->in.open ) && ( ( rc = usbblk_open ( usbblk ) ) != 0 ) )
                goto err_open;

        /* Start new command */
        if ( ( rc = usbblk_start ( usbblk, scsicmd ) ) != 0 )
                goto err_start;

        /* Attach to parent interface and return */
        intf_plug_plug ( &usbblk->data, data );
        return cmd->tag;

        usbblk_stop ( usbblk, rc );
 err_start:
        usbblk_close ( usbblk );
 err_open:
        return rc;
}

/**
 * Close SCSI interface
 *
 * @v usbblk            USB block device
 * @v rc                Reason for close
 */
static void usbblk_scsi_close ( struct usbblk_device *usbblk, int rc ) {

        /* Restart interfaces */
        intfs_restart ( rc, &usbblk->scsi, &usbblk->data, NULL );

        /* Stop any in-progress command */
        usbblk_stop ( usbblk, rc );

        /* Close endpoints */
        usbblk_close ( usbblk );

        /* Flag as closed */
        usbblk->opened = 0;
}

/**
 * Describe as an EFI device path
 *
 * @v usbblk            USB block device
 * @ret path            EFI device path, or NULL on error
 */
static EFI_DEVICE_PATH_PROTOCOL *
usbblk_efi_describe ( struct usbblk_device *usbblk ) {

        return efi_usb_path ( usbblk->func );
}

/** SCSI command interface operations */
static struct interface_operation usbblk_scsi_operations[] = {
        INTF_OP ( scsi_command, struct usbblk_device *, usbblk_scsi_command ),
        INTF_OP ( xfer_window, struct usbblk_device *, usbblk_scsi_window ),
        INTF_OP ( intf_close, struct usbblk_device *, usbblk_scsi_close ),
        EFI_INTF_OP ( efi_describe, struct usbblk_device *,
                      usbblk_efi_describe ),
};

/** SCSI command interface descriptor */
static struct interface_descriptor usbblk_scsi_desc =
        INTF_DESC ( struct usbblk_device, scsi, usbblk_scsi_operations );

/******************************************************************************
 *
 * SAN device interface
 *
 ******************************************************************************
 */

/**
 * Find USB block device
 *
 * @v name              USB block device name
 * @ret usbblk          USB block device, or NULL
 */
static struct usbblk_device * usbblk_find ( const char *name ) {
        struct usbblk_device *usbblk;

        /* Look for matching device */
        list_for_each_entry ( usbblk, &usbblk_devices, list ) {
                if ( strcmp ( usbblk->func->name, name ) == 0 )
                        return usbblk;
        }

        return NULL;
}

/**
 * Open USB block device URI
 *
 * @v parent            Parent interface
 * @v uri               URI
 * @ret rc              Return status code
 */
static int usbblk_open_uri ( struct interface *parent, struct uri *uri ) {
        static struct scsi_lun lun;
        struct usbblk_device *usbblk;
        int rc;

        /* Sanity check */
        if ( ! uri->opaque )
                return -EINVAL;

        /* Find matching device */
        usbblk = usbblk_find ( uri->opaque );
        if ( ! usbblk )
                return -ENOENT;

        /* Fail if device is already open */
        if ( usbblk->opened )
                return -EBUSY;

        /* Open SCSI device */
        if ( ( rc = scsi_open ( parent, &usbblk->scsi, &lun ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not open SCSI device: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                return rc;
        }

        /* Mark as opened */
        usbblk->opened = 1;

        return 0;
}

/** USB block device URI opener */
struct uri_opener usbblk_uri_opener __uri_opener = {
        .scheme = "usb",
        .open = usbblk_open_uri,
};

/******************************************************************************
 *
 * USB interface
 *
 ******************************************************************************
 */

/**
 * Probe device
 *
 * @v func              USB function
 * @v config            Configuration descriptor
 * @ret rc              Return status code
 */
static int usbblk_probe ( struct usb_function *func,
                          struct usb_configuration_descriptor *config ) {
        struct usb_device *usb = func->usb;
        struct usbblk_device *usbblk;
        struct usb_interface_descriptor *desc;
        int rc;

        /* Allocate and initialise structure */
        usbblk = zalloc ( sizeof ( *usbblk ) );
        if ( ! usbblk ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        usbblk->func = func;
        usb_endpoint_init ( &usbblk->out, usb, &usbblk_out_operations );
        usb_endpoint_init ( &usbblk->in, usb, &usbblk_in_operations );
        usb_refill_init ( &usbblk->in, 0, USBBLK_MAX_LEN, USBBLK_MAX_FILL );
        intf_init ( &usbblk->scsi, &usbblk_scsi_desc, &usbblk->refcnt );
        intf_init ( &usbblk->data, &usbblk_data_desc, &usbblk->refcnt );
        process_init_stopped ( &usbblk->process, &usbblk_process_desc,
                               &usbblk->refcnt );

        /* Locate interface descriptor */
        desc = usb_interface_descriptor ( config, func->interface[0], 0 );
        if ( ! desc ) {
                DBGC ( usbblk, "USBBLK %s missing interface descriptor\n",
                       usbblk->func->name );
                rc = -ENOENT;
                goto err_desc;
        }

        /* Describe endpoints */
        if ( ( rc = usb_endpoint_described ( &usbblk->out, config, desc,
                                             USB_BULK_OUT, 0 ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not describe bulk OUT: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_out;
        }
        if ( ( rc = usb_endpoint_described ( &usbblk->in, config, desc,
                                             USB_BULK_IN, 0 ) ) != 0 ) {
                DBGC ( usbblk, "USBBLK %s could not describe bulk IN: %s\n",
                       usbblk->func->name, strerror ( rc ) );
                goto err_in;
        }

        /* Add to list of devices */
        list_add_tail ( &usbblk->list, &usbblk_devices );

        usb_func_set_drvdata ( func, usbblk );
        return 0;

 err_in:
 err_out:
 err_desc:
        ref_put ( &usbblk->refcnt );
 err_alloc:
        return rc;
}

/**
 * Remove device
 *
 * @v func              USB function
 */
static void usbblk_remove ( struct usb_function *func ) {
        struct usbblk_device *usbblk = usb_func_get_drvdata ( func );

        /* Remove from list of devices */
        list_del ( &usbblk->list );

        /* Close all interfaces */
        usbblk_scsi_close ( usbblk, -ENODEV );

        /* Shut down interfaces */
        intfs_shutdown ( -ENODEV, &usbblk->scsi, &usbblk->data, NULL );

        /* Drop reference */
        ref_put ( &usbblk->refcnt );
}

/** Mass storage class device IDs */
static struct usb_device_id usbblk_ids[] = {
        {
                .name = "usbblk",
                .vendor = USB_ANY_ID,
                .product = USB_ANY_ID,
        },
};

/** Mass storage driver */
struct usb_driver usbblk_driver __usb_driver = {
        .ids = usbblk_ids,
        .id_count = ( sizeof ( usbblk_ids ) / sizeof ( usbblk_ids[0] ) ),
        .class = USB_CLASS_ID ( USB_CLASS_MSC, USB_SUBCLASS_MSC_SCSI,
                                USB_PROTOCOL_MSC_BULK ),
        .score = USB_SCORE_NORMAL,
        .probe = usbblk_probe,
        .remove = usbblk_remove,
};