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 <scsi/scsi.h>
  47 #include <scsi/scsi_cmnd.h>
  48
  49 #include "usb.h"
  50 #include "protocol.h"
  51 #include "debug.h"
  52 #include "scsiglue.h"
  53 #include "transport.h"
  54
  55 /***********************************************************************
  56  * Protocol routines
  57  ***********************************************************************/
  58
  59 void usb_stor_pad12_command(struct scsi_cmnd *srb, struct us_data *us)
  60 {
  61         /*
  62          * Pad the SCSI command with zeros out to 12 bytes.  If the
  63          * command already is 12 bytes or longer, leave it alone.
  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         /* send the command to the transport layer */
  72         usb_stor_invoke_transport(srb, us);
  73 }
  74
  75 void usb_stor_ufi_command(struct scsi_cmnd *srb, struct us_data *us)
  76 {
  77         /* fix some commands -- this is a form of mode translation
  78          * UFI devices only accept 12 byte long commands
  79          *
  80          * NOTE: This only works because a scsi_cmnd struct field contains
  81          * a unsigned char cmnd[16], so we know we have storage available
  82          */
  83
  84         /* Pad the ATAPI command with zeros */
  85         for (; srb->cmd_len<12; srb->cmd_len++)
  86                 srb->cmnd[srb->cmd_len] = 0;
  87
  88         /* set command length to 12 bytes (this affects the transport layer) */
  89         srb->cmd_len = 12;
  90
  91         /* XXX We should be constantly re-evaluating the need for these */
  92
  93         /* determine the correct data length for these commands */
  94         switch (srb->cmnd[0]) {
  95
  96                 /* for INQUIRY, UFI devices only ever return 36 bytes */
  97         case INQUIRY:
  98                 srb->cmnd[4] = 36;
  99                 break;
 100
 101                 /* again, for MODE_SENSE_10, we get the minimum (8) */
 102         case MODE_SENSE_10:
 103                 srb->cmnd[7] = 0;
 104                 srb->cmnd[8] = 8;
 105                 break;
 106
 107                 /* for REQUEST_SENSE, UFI devices only ever return 18 bytes */
 108         case REQUEST_SENSE:
 109                 srb->cmnd[4] = 18;
 110                 break;
 111         } /* end switch on cmnd[0] */
 112
 113         /* send the command to the transport layer */
 114         usb_stor_invoke_transport(srb, us);
 115 }
 116
 117 void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
 118                                        struct us_data *us)
 119 {
 120         /* send the command to the transport layer */
 121         usb_stor_invoke_transport(srb, us);
 122 }
 123 EXPORT_SYMBOL_GPL(usb_stor_transparent_scsi_command);
 124
 125 /***********************************************************************
 126  * Scatter-gather transfer buffer access routines
 127  ***********************************************************************/
 128
 129 /* Copy a buffer of length buflen to/from the srb's transfer buffer.
 130  * Update the **sgptr and *offset variables so that the next copy will
 131  * pick up from where this one left off.
 132  */
 133 unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
 134         unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
 135         unsigned int *offset, enum xfer_buf_dir dir)
 136 {
 137         unsigned int cnt;
 138         struct scatterlist *sg = *sgptr;
 139
 140         /* We have to go through the list one entry
 141          * at a time.  Each s-g entry contains some number of pages, and
 142          * each page has to be kmap()'ed separately.  If the page is already
 143          * in kernel-addressable memory then kmap() will return its address.
 144          * If the page is not directly accessible -- such as a user buffer
 145          * located in high memory -- then kmap() will map it to a temporary
 146          * position in the kernel's virtual address space.
 147          */
 148
 149         if (!sg)
 150                 sg = scsi_sglist(srb);
 151
 152         /* This loop handles a single s-g list entry, which may
 153          * include multiple pages.  Find the initial page structure
 154          * and the starting offset within the page, and update
 155          * the *offset and **sgptr values for the next loop.
 156          */
 157         cnt = 0;
 158         while (cnt < buflen && sg) {
 159                 struct page *page = sg_page(sg) +
 160                                 ((sg->offset + *offset) >> PAGE_SHIFT);
 161                 unsigned int poff = (sg->offset + *offset) & (PAGE_SIZE-1);
 162                 unsigned int sglen = sg->length - *offset;
 163
 164                 if (sglen > buflen - cnt) {
 165
 166                         /* Transfer ends within this s-g entry */
 167                         sglen = buflen - cnt;
 168                         *offset += sglen;
 169                 } else {
 170
 171                         /* Transfer continues to next s-g entry */
 172                         *offset = 0;
 173                         sg = sg_next(sg);
 174                 }
 175
 176                 /* Transfer the data for all the pages in this
 177                         * s-g entry.  For each page: call kmap(), do the
 178                         * transfer, and call kunmap() immediately after. */
 179                 while (sglen > 0) {
 180                         unsigned int plen = min(sglen, (unsigned int)
 181                                         PAGE_SIZE - poff);
 182                         unsigned char *ptr = kmap(page);
 183
 184                         if (dir == TO_XFER_BUF)
 185                                 memcpy(ptr + poff, buffer + cnt, plen);
 186                         else
 187                                 memcpy(buffer + cnt, ptr + poff, plen);
 188                         kunmap(page);
 189
 190                         /* Start at the beginning of the next page */
 191                         poff = 0;
 192                         ++page;
 193                         cnt += plen;
 194                         sglen -= plen;
 195                 }
 196         }
 197         *sgptr = sg;
 198
 199         /* Return the amount actually transferred */
 200         return cnt;
 201 }
 202 EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
 203
 204 /* Store the contents of buffer into srb's transfer buffer and set the
 205  * SCSI residue.
 206  */
 207 void usb_stor_set_xfer_buf(unsigned char *buffer,
 208         unsigned int buflen, struct scsi_cmnd *srb)
 209 {
 210         unsigned int offset = 0;
 211         struct scatterlist *sg = NULL;
 212
 213         buflen = min(buflen, scsi_bufflen(srb));
 214         buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
 215                         TO_XFER_BUF);
 216         if (buflen < scsi_bufflen(srb))
 217                 scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
 218 }
 219 EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);