drivers/usb/storage/protocol.c

   1 /*
   2  * Driver for USB Mass Storage compliant devices
   3  *
   4  * Current development and maintenance by:
   5  *   (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
   6  *
   7  * Developed with the assistance of:
   8  *   (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org)
   9  *   (c) 2002 Alan Stern (stern@rowland.org)
  10  *
  11  * Initial work by:
  12  *   (c) 1999 Michael Gee (michael@linuxspecific.com)
  13  *
  14  * This driver is based on the 'USB Mass Storage Class' document. This
  15  * describes in detail the protocol used to communicate with such
  16  * devices.  Clearly, the designers had SCSI and ATAPI commands in
  17  * mind when they created this document.  The commands are all very
  18  * similar to commands in the SCSI-II and ATAPI specifications.
  19  *
  20  * It is important to note that in a number of cases this class
  21  * exhibits class-specific exemptions from the USB specification.
  22  * Notably the usage of NAK, STALL and ACK differs from the norm, in
  23  * that they are used to communicate wait, failed and OK on commands.
  24  *
  25  * Also, for certain devices, the interrupt endpoint is used to convey
  26  * status of a command.
  27  *
  28  * Please see http://www.one-eyed-alien.net/~mdharm/linux-usb for more
  29  * information about this driver.
  30  *
  31  * This program is free software; you can redistribute it and/or modify it
  32  * under the terms of the GNU General Public License as published by the
  33  * Free Software Foundation; either version 2, or (at your option) any
  34  * later version.
  35  *
  36  * This program is distributed in the hope that it will be useful, but
  37  * WITHOUT ANY WARRANTY; without even the implied warranty of
  38  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  39  * General Public License for more details.
  40  *
  41  * You should have received a copy of the GNU General Public License along
  42  * with this program; if not, write to the Free Software Foundation, Inc.,
  43  * 675 Mass Ave, Cambridge, MA 02139, USA.
  44  */
  45
  46 #include <linux/highmem.h>
  47 #include <linux/export.h>
  48 #include <scsi/scsi.h>
  49 #include <scsi/scsi_cmnd.h>
  50
  51 #include "usb.h"
  52 #include "protocol.h"
  53 #include "debug.h"
  54 #include "scsiglue.h"
  55 #include "transport.h"
  56
  57 /***********************************************************************
  58  * Protocol routines
  59  ***********************************************************************/
  60
  61 void usb_stor_pad12_command(struct scsi_cmnd *srb, struct us_data *us)
  62 {
  63         /*
  64          * Pad the SCSI command with zeros out to 12 bytes.  If the
  65          * command already is 12 bytes or longer, leave it alone.
  66          *
  67          * NOTE: This only works because a scsi_cmnd struct field contains
  68          * a unsigned char cmnd[16], so we know we have storage available
  69          */
  70         for (; srb->cmd_len < 12; srb->cmd_len++)
  71                 srb->cmnd[srb->cmd_len] = 0;
  72
  73         /* send the command to the transport layer */
  74         usb_stor_invoke_transport(srb, us);
  75 }
  76
  77 void usb_stor_ufi_command(struct scsi_cmnd *srb, struct us_data *us)
  78 {
  79         /*
  80          * fix some commands -- this is a form of mode translation
  81          * UFI devices only accept 12 byte long commands
  82          *
  83          * NOTE: This only works because a scsi_cmnd struct field contains
  84          * a unsigned char cmnd[16], so we know we have storage available
  85          */
  86
  87         /* Pad the ATAPI command with zeros */
  88         for (; srb->cmd_len < 12; srb->cmd_len++)
  89                 srb->cmnd[srb->cmd_len] = 0;
  90
  91         /* set command length to 12 bytes (this affects the transport layer) */
  92         srb->cmd_len = 12;
  93
  94         /* XXX We should be constantly re-evaluating the need for these */
  95
  96         /* determine the correct data length for these commands */
  97         switch (srb->cmnd[0]) {
  98
  99                 /* for INQUIRY, UFI devices only ever return 36 bytes */
 100         case INQUIRY:
 101                 srb->cmnd[4] = 36;
 102                 break;
 103
 104                 /* again, for MODE_SENSE_10, we get the minimum (8) */
 105         case MODE_SENSE_10:
 106                 srb->cmnd[7] = 0;
 107                 srb->cmnd[8] = 8;
 108                 break;
 109
 110                 /* for REQUEST_SENSE, UFI devices only ever return 18 bytes */
 111         case REQUEST_SENSE:
 112                 srb->cmnd[4] = 18;
 113                 break;
 114         } /* end switch on cmnd[0] */
 115
 116         /* send the command to the transport layer */
 117         usb_stor_invoke_transport(srb, us);
 118 }
 119
 120 void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
 121                                        struct us_data *us)
 122 {
 123         /* send the command to the transport layer */
 124         usb_stor_invoke_transport(srb, us);
 125 }
 126 EXPORT_SYMBOL_GPL(usb_stor_transparent_scsi_command);
 127
 128 /***********************************************************************
 129  * Scatter-gather transfer buffer access routines
 130  ***********************************************************************/
 131
 132 /*
 133  * Copy a buffer of length buflen to/from the srb's transfer buffer.
 134  * Update the **sgptr and *offset variables so that the next copy will
 135  * pick up from where this one left off.
 136  */
 137 unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
 138         unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
 139         unsigned int *offset, enum xfer_buf_dir dir)
 140 {
 141         unsigned int cnt = 0;
 142         struct scatterlist *sg = *sgptr;
 143         struct sg_mapping_iter miter;
 144         unsigned int nents = scsi_sg_count(srb);
 145
 146         if (sg)
 147                 nents = sg_nents(sg);
 148         else
 149                 sg = scsi_sglist(srb);
 150
 151         sg_miter_start(&miter, sg, nents, dir == FROM_XFER_BUF ?
 152                 SG_MITER_FROM_SG: SG_MITER_TO_SG);
 153
 154         if (!sg_miter_skip(&miter, *offset))
 155                 return cnt;
 156
 157         while (sg_miter_next(&miter) && cnt < buflen) {
 158                 unsigned int len = min_t(unsigned int, miter.length,
 159                                 buflen - cnt);
 160
 161                 if (dir == FROM_XFER_BUF)
 162                         memcpy(buffer + cnt, miter.addr, len);
 163                 else
 164                         memcpy(miter.addr, buffer + cnt, len);
 165
 166                 if (*offset + len < miter.piter.sg->length) {
 167                         *offset += len;
 168                         *sgptr = miter.piter.sg;
 169                 } else {
 170                         *offset = 0;
 171                         *sgptr = sg_next(miter.piter.sg);
 172                 }
 173                 cnt += len;
 174         }
 175         sg_miter_stop(&miter);
 176
 177         return cnt;
 178 }
 179 EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
 180
 181 /*
 182  * Store the contents of buffer into srb's transfer buffer and set the
 183  * SCSI residue.
 184  */
 185 void usb_stor_set_xfer_buf(unsigned char *buffer,
 186         unsigned int buflen, struct scsi_cmnd *srb)
 187 {
 188         unsigned int offset = 0;
 189         struct scatterlist *sg = NULL;
 190
 191         buflen = min(buflen, scsi_bufflen(srb));
 192         buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
 193                         TO_XFER_BUF);
 194         if (buflen < scsi_bufflen(srb))
 195                 scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
 196 }
 197 EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);