drivers/usb/storage/protocol.c

   1 /* Driver for USB Mass Storage compliant devices
   2  *
   3  * $Id: protocol.c,v 1.14 2002/04/22 03:39:43 mdharm Exp $
   4  *
   5  * Current development and maintenance by:
   6  *   (c) 1999-2002 Matthew Dharm (mdharm-usb@one-eyed-alien.net)
   7  *
   8  * Developed with the assistance of:
   9  *   (c) 2000 David L. Brown, Jr. (usb-storage@davidb.org)
  10  *   (c) 2002 Alan Stern (stern@rowland.org)
  11  *
  12  * Initial work by:
  13  *   (c) 1999 Michael Gee (michael@linuxspecific.com)
  14  *
  15  * This driver is based on the 'USB Mass Storage Class' document. This
  16  * describes in detail the protocol used to communicate with such
  17  * devices.  Clearly, the designers had SCSI and ATAPI commands in
  18  * mind when they created this document.  The commands are all very
  19  * similar to commands in the SCSI-II and ATAPI specifications.
  20  *
  21  * It is important to note that in a number of cases this class
  22  * exhibits class-specific exemptions from the USB specification.
  23  * Notably the usage of NAK, STALL and ACK differs from the norm, in
  24  * that they are used to communicate wait, failed and OK on commands.
  25  *
  26  * Also, for certain devices, the interrupt endpoint is used to convey
  27  * status of a command.
  28  *
  29  * Please see http://www.one-eyed-alien.net/~mdharm/linux-usb for more
  30  * information about this driver.
  31  *
  32  * This program is free software; you can redistribute it and/or modify it
  33  * under the terms of the GNU General Public License as published by the
  34  * Free Software Foundation; either version 2, or (at your option) any
  35  * later version.
  36  *
  37  * This program is distributed in the hope that it will be useful, but
  38  * WITHOUT ANY WARRANTY; without even the implied warranty of
  39  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  40  * General Public License for more details.
  41  *
  42  * You should have received a copy of the GNU General Public License along
  43  * with this program; if not, write to the Free Software Foundation, Inc.,
  44  * 675 Mass Ave, Cambridge, MA 02139, USA.
  45  */
  46
  47 #include <linux/highmem.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_qic157_command(struct scsi_cmnd *srb, struct us_data *us)
  62 {
  63         /* Pad the ATAPI command with zeros
  64          *
  65          * NOTE: This only works because a scsi_cmnd struct field contains
  66          * a unsigned char cmnd[16], so we know we have storage available
  67          */
  68         for (; srb->cmd_len<12; srb->cmd_len++)
  69                 srb->cmnd[srb->cmd_len] = 0;
  70
  71         /* set command length to 12 bytes */
  72         srb->cmd_len = 12;
  73
  74         /* send the command to the transport layer */
  75         usb_stor_invoke_transport(srb, us);
  76 }
  77
  78 void usb_stor_ATAPI_command(struct scsi_cmnd *srb, struct us_data *us)
  79 {
  80         /* Pad the ATAPI command with zeros
  81          *
  82          * NOTE: This only works because a scsi_cmnd struct field contains
  83          * a unsigned char cmnd[16], so we know we have storage available
  84          */
  85
  86         /* Pad the ATAPI command with zeros */
  87         for (; srb->cmd_len<12; srb->cmd_len++)
  88                 srb->cmnd[srb->cmd_len] = 0;
  89
  90         /* set command length to 12 bytes */
  91         srb->cmd_len = 12;
  92
  93         /* send the command to the transport layer */
  94         usb_stor_invoke_transport(srb, us);
  95 }
  96
  97
  98 void usb_stor_ufi_command(struct scsi_cmnd *srb, struct us_data *us)
  99 {
 100         /* fix some commands -- this is a form of mode translation
 101          * UFI devices only accept 12 byte long commands
 102          *
 103          * NOTE: This only works because a scsi_cmnd struct field contains
 104          * a unsigned char cmnd[16], so we know we have storage available
 105          */
 106
 107         /* Pad the ATAPI command with zeros */
 108         for (; srb->cmd_len<12; srb->cmd_len++)
 109                 srb->cmnd[srb->cmd_len] = 0;
 110
 111         /* set command length to 12 bytes (this affects the transport layer) */
 112         srb->cmd_len = 12;
 113
 114         /* XXX We should be constantly re-evaluating the need for these */
 115
 116         /* determine the correct data length for these commands */
 117         switch (srb->cmnd[0]) {
 118
 119                 /* for INQUIRY, UFI devices only ever return 36 bytes */
 120         case INQUIRY:
 121                 srb->cmnd[4] = 36;
 122                 break;
 123
 124                 /* again, for MODE_SENSE_10, we get the minimum (8) */
 125         case MODE_SENSE_10:
 126                 srb->cmnd[7] = 0;
 127                 srb->cmnd[8] = 8;
 128                 break;
 129
 130                 /* for REQUEST_SENSE, UFI devices only ever return 18 bytes */
 131         case REQUEST_SENSE:
 132                 srb->cmnd[4] = 18;
 133                 break;
 134         } /* end switch on cmnd[0] */
 135
 136         /* send the command to the transport layer */
 137         usb_stor_invoke_transport(srb, us);
 138 }
 139
 140 void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
 141                                        struct us_data *us)
 142 {
 143         /* send the command to the transport layer */
 144         usb_stor_invoke_transport(srb, us);
 145 }
 146
 147 /***********************************************************************
 148  * Scatter-gather transfer buffer access routines
 149  ***********************************************************************/
 150
 151 /* Copy a buffer of length buflen to/from the srb's transfer buffer.
 152  * Update the **sgptr and *offset variables so that the next copy will
 153  * pick up from where this one left off.
 154  */
 155 unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
 156         unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
 157         unsigned int *offset, enum xfer_buf_dir dir)
 158 {
 159         unsigned int cnt;
 160         struct scatterlist *sg = *sgptr;
 161
 162         /* We have to go through the list one entry
 163          * at a time.  Each s-g entry contains some number of pages, and
 164          * each page has to be kmap()'ed separately.  If the page is already
 165          * in kernel-addressable memory then kmap() will return its address.
 166          * If the page is not directly accessible -- such as a user buffer
 167          * located in high memory -- then kmap() will map it to a temporary
 168          * position in the kernel's virtual address space.
 169          */
 170
 171         if (!sg)
 172                 sg = scsi_sglist(srb);
 173
 174         /* This loop handles a single s-g list entry, which may
 175          * include multiple pages.  Find the initial page structure
 176          * and the starting offset within the page, and update
 177          * the *offset and **sgptr values for the next loop.
 178          */
 179         cnt = 0;
 180         while (cnt < buflen && sg) {
 181                 struct page *page = sg_page(sg) +
 182                                 ((sg->offset + *offset) >> PAGE_SHIFT);
 183                 unsigned int poff = (sg->offset + *offset) & (PAGE_SIZE-1);
 184                 unsigned int sglen = sg->length - *offset;
 185
 186                 if (sglen > buflen - cnt) {
 187
 188                         /* Transfer ends within this s-g entry */
 189                         sglen = buflen - cnt;
 190                         *offset += sglen;
 191                 } else {
 192
 193                         /* Transfer continues to next s-g entry */
 194                         *offset = 0;
 195                         sg = sg_next(sg);
 196                 }
 197
 198                 /* Transfer the data for all the pages in this
 199                         * s-g entry.  For each page: call kmap(), do the
 200                         * transfer, and call kunmap() immediately after. */
 201                 while (sglen > 0) {
 202                         unsigned int plen = min(sglen, (unsigned int)
 203                                         PAGE_SIZE - poff);
 204                         unsigned char *ptr = kmap(page);
 205
 206                         if (dir == TO_XFER_BUF)
 207                                 memcpy(ptr + poff, buffer + cnt, plen);
 208                         else
 209                                 memcpy(buffer + cnt, ptr + poff, plen);
 210                         kunmap(page);
 211
 212                         /* Start at the beginning of the next page */
 213                         poff = 0;
 214                         ++page;
 215                         cnt += plen;
 216                         sglen -= plen;
 217                 }
 218         }
 219         *sgptr = sg;
 220
 221         /* Return the amount actually transferred */
 222         return cnt;
 223 }
 224
 225 /* Store the contents of buffer into srb's transfer buffer and set the
 226  * SCSI residue.
 227  */
 228 void usb_stor_set_xfer_buf(unsigned char *buffer,
 229         unsigned int buflen, struct scsi_cmnd *srb)
 230 {
 231         unsigned int offset = 0;
 232         struct scatterlist *sg = NULL;
 233
 234         buflen = min(buflen, scsi_bufflen(srb));
 235         buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
 236                         TO_XFER_BUF);
 237         if (buflen < scsi_bufflen(srb))
 238                 scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
 239 }