// SPDX-License-Identifier: GPL-2.0+
/*
 * Driver for USB Mass Storage compliant devices
 *
 * Current development and maintenance by:
 *   (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
 *
 * Developed with the assistance of:
 *   (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org)
 *   (c) 2002 Alan Stern (stern@rowland.org)
 *
 * Initial work by:
 *   (c) 1999 Michael Gee (michael@linuxspecific.com)
 *
 * This driver is based on the 'USB Mass Storage Class' document. This
 * describes in detail the protocol used to communicate with such
 * devices.  Clearly, the designers had SCSI and ATAPI commands in
 * mind when they created this document.  The commands are all very
 * similar to commands in the SCSI-II and ATAPI specifications.
 *
 * It is important to note that in a number of cases this class
 * exhibits class-specific exemptions from the USB specification.
 * Notably the usage of NAK, STALL and ACK differs from the norm, in
 * that they are used to communicate wait, failed and OK on commands.
 *
 * Also, for certain devices, the interrupt endpoint is used to convey
 * status of a command.
 */

#include <linux/highmem.h>
#include <linux/export.h>
#include <scsi/scsi.h>
#include <scsi/scsi_cmnd.h>

#include "usb.h"
#include "protocol.h"
#include "debug.h"
#include "scsiglue.h"
#include "transport.h"

/***********************************************************************
 * Protocol routines
 ***********************************************************************/

void usb_stor_pad12_command(struct scsi_cmnd *srb, struct us_data *us)
{
        /*
         * Pad the SCSI command with zeros out to 12 bytes.  If the
         * command already is 12 bytes or longer, leave it alone.
         *
         * NOTE: This only works because a scsi_cmnd struct field contains
         * a unsigned char cmnd[16], so we know we have storage available
         */
        for (; srb->cmd_len < 12; srb->cmd_len++)
                srb->cmnd[srb->cmd_len] = 0;

        /* send the command to the transport layer */
        usb_stor_invoke_transport(srb, us);
}

void usb_stor_ufi_command(struct scsi_cmnd *srb, struct us_data *us)
{
        /*
         * fix some commands -- this is a form of mode translation
         * UFI devices only accept 12 byte long commands
         *
         * NOTE: This only works because a scsi_cmnd struct field contains
         * a unsigned char cmnd[16], so we know we have storage available
         */

        /* Pad the ATAPI command with zeros */
        for (; srb->cmd_len < 12; srb->cmd_len++)
                srb->cmnd[srb->cmd_len] = 0;

        /* set command length to 12 bytes (this affects the transport layer) */
        srb->cmd_len = 12;

        /* XXX We should be constantly re-evaluating the need for these */

        /* determine the correct data length for these commands */
        switch (srb->cmnd[0]) {

                /* for INQUIRY, UFI devices only ever return 36 bytes */
        case INQUIRY:
                srb->cmnd[4] = 36;
                break;

                /* again, for MODE_SENSE_10, we get the minimum (8) */
        case MODE_SENSE_10:
                srb->cmnd[7] = 0;
                srb->cmnd[8] = 8;
                break;

                /* for REQUEST_SENSE, UFI devices only ever return 18 bytes */
        case REQUEST_SENSE:
                srb->cmnd[4] = 18;
                break;
        } /* end switch on cmnd[0] */

        /* send the command to the transport layer */
        usb_stor_invoke_transport(srb, us);
}

void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
                                       struct us_data *us)
{
        /* send the command to the transport layer */
        usb_stor_invoke_transport(srb, us);
}
EXPORT_SYMBOL_GPL(usb_stor_transparent_scsi_command);

/***********************************************************************
 * Scatter-gather transfer buffer access routines
 ***********************************************************************/

/*
 * Copy a buffer of length buflen to/from the srb's transfer buffer.
 * Update the **sgptr and *offset variables so that the next copy will
 * pick up from where this one left off.
 */
unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
        unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
        unsigned int *offset, enum xfer_buf_dir dir)
{
        unsigned int cnt = 0;
        struct scatterlist *sg = *sgptr;
        struct sg_mapping_iter miter;
        unsigned int nents = scsi_sg_count(srb);

        if (sg)
                nents = sg_nents(sg);
        else
                sg = scsi_sglist(srb);

        sg_miter_start(&miter, sg, nents, dir == FROM_XFER_BUF ?
                SG_MITER_FROM_SG: SG_MITER_TO_SG);

        if (!sg_miter_skip(&miter, *offset))
                return cnt;

        while (sg_miter_next(&miter) && cnt < buflen) {
                unsigned int len = min(miter.length, buflen - cnt);

                if (dir == FROM_XFER_BUF)
                        memcpy(buffer + cnt, miter.addr, len);
                else
                        memcpy(miter.addr, buffer + cnt, len);

                if (*offset + len < miter.piter.sg->length) {
                        *offset += len;
                        *sgptr = miter.piter.sg;
                } else {
                        *offset = 0;
                        *sgptr = sg_next(miter.piter.sg);
                }
                cnt += len;
        }
        sg_miter_stop(&miter);

        return cnt;
}
EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);

/*
 * Store the contents of buffer into srb's transfer buffer and set the
 * SCSI residue.
 */
void usb_stor_set_xfer_buf(unsigned char *buffer,
        unsigned int buflen, struct scsi_cmnd *srb)
{
        unsigned int offset = 0;
        struct scatterlist *sg = NULL;

        buflen = min(buflen, scsi_bufflen(srb));
        buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
                        TO_XFER_BUF);
        if (buflen < scsi_bufflen(srb))
                scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
}
EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);