drivers/usb/storage/protocol.c

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