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         /* Pad the SCSI command with zeros out to 12 bytes
  63          *
  64          * NOTE: This only works because a scsi_cmnd struct field contains
  65          * a unsigned char cmnd[16], so we know we have storage available
  66          */
  67         for (; srb->cmd_len<12; srb->cmd_len++)
  68                 srb->cmnd[srb->cmd_len] = 0;
  69
  70         /* set command length to 12 bytes */
  71         srb->cmd_len = 12;
  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         /* fix some commands -- this is a form of mode translation
  80          * UFI devices only accept 12 byte long commands
  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 (this affects the transport layer) */
  91         srb->cmd_len = 12;
  92
  93         /* XXX We should be constantly re-evaluating the need for these */
  94
  95         /* determine the correct data length for these commands */
  96         switch (srb->cmnd[0]) {
  97
  98                 /* for INQUIRY, UFI devices only ever return 36 bytes */
  99         case INQUIRY:
 100                 srb->cmnd[4] = 36;
 101                 break;
 102
 103                 /* again, for MODE_SENSE_10, we get the minimum (8) */
 104         case MODE_SENSE_10:
 105                 srb->cmnd[7] = 0;
 106                 srb->cmnd[8] = 8;
 107                 break;
 108
 109                 /* for REQUEST_SENSE, UFI devices only ever return 18 bytes */
 110         case REQUEST_SENSE:
 111                 srb->cmnd[4] = 18;
 112                 break;
 113         } /* end switch on cmnd[0] */
 114
 115         /* send the command to the transport layer */
 116         usb_stor_invoke_transport(srb, us);
 117 }
 118
 119 void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
 120                                        struct us_data *us)
 121 {
 122         /* send the command to the transport layer */
 123         usb_stor_invoke_transport(srb, us);
 124 }
 125 EXPORT_SYMBOL_GPL(usb_stor_transparent_scsi_command);
 126
 127 /***********************************************************************
 128  * Scatter-gather transfer buffer access routines
 129  ***********************************************************************/
 130
 131 /* Copy a buffer of length buflen to/from the srb's transfer buffer.
 132  * Update the **sgptr and *offset variables so that the next copy will
 133  * pick up from where this one left off.
 134  */
 135 unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
 136         unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
 137         unsigned int *offset, enum xfer_buf_dir dir)
 138 {
 139         unsigned int cnt;
 140         struct scatterlist *sg = *sgptr;
 141
 142         /* We have to go through the list one entry
 143          * at a time.  Each s-g entry contains some number of pages, and
 144          * each page has to be kmap()'ed separately.  If the page is already
 145          * in kernel-addressable memory then kmap() will return its address.
 146          * If the page is not directly accessible -- such as a user buffer
 147          * located in high memory -- then kmap() will map it to a temporary
 148          * position in the kernel's virtual address space.
 149          */
 150
 151         if (!sg)
 152                 sg = scsi_sglist(srb);
 153
 154         /* This loop handles a single s-g list entry, which may
 155          * include multiple pages.  Find the initial page structure
 156          * and the starting offset within the page, and update
 157          * the *offset and **sgptr values for the next loop.
 158          */
 159         cnt = 0;
 160         while (cnt < buflen && sg) {
 161                 struct page *page = sg_page(sg) +
 162                                 ((sg->offset + *offset) >> PAGE_SHIFT);
 163                 unsigned int poff = (sg->offset + *offset) & (PAGE_SIZE-1);
 164                 unsigned int sglen = sg->length - *offset;
 165
 166                 if (sglen > buflen - cnt) {
 167
 168                         /* Transfer ends within this s-g entry */
 169                         sglen = buflen - cnt;
 170                         *offset += sglen;
 171                 } else {
 172
 173                         /* Transfer continues to next s-g entry */
 174                         *offset = 0;
 175                         sg = sg_next(sg);
 176                 }
 177
 178                 /* Transfer the data for all the pages in this
 179                         * s-g entry.  For each page: call kmap(), do the
 180                         * transfer, and call kunmap() immediately after. */
 181                 while (sglen > 0) {
 182                         unsigned int plen = min(sglen, (unsigned int)
 183                                         PAGE_SIZE - poff);
 184                         unsigned char *ptr = kmap(page);
 185
 186                         if (dir == TO_XFER_BUF)
 187                                 memcpy(ptr + poff, buffer + cnt, plen);
 188                         else
 189                                 memcpy(buffer + cnt, ptr + poff, plen);
 190                         kunmap(page);
 191
 192                         /* Start at the beginning of the next page */
 193                         poff = 0;
 194                         ++page;
 195                         cnt += plen;
 196                         sglen -= plen;
 197                 }
 198         }
 199         *sgptr = sg;
 200
 201         /* Return the amount actually transferred */
 202         return cnt;
 203 }
 204 EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
 205
 206 /* Store the contents of buffer into srb's transfer buffer and set the
 207  * SCSI residue.
 208  */
 209 void usb_stor_set_xfer_buf(unsigned char *buffer,
 210         unsigned int buflen, struct scsi_cmnd *srb)
 211 {
 212         unsigned int offset = 0;
 213         struct scatterlist *sg = NULL;
 214
 215         buflen = min(buflen, scsi_bufflen(srb));
 216         buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
 217                         TO_XFER_BUF);
 218         if (buflen < scsi_bufflen(srb))
 219                 scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
 220 }
 221 EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);