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         /* Pad the SCSI command with zeros out to 12 bytes
  62          *
  63          * NOTE: This only works because a scsi_cmnd struct field contains
  64          * a unsigned char cmnd[16], so we know we have storage available
  65          */
  66         for (; srb->cmd_len<12; srb->cmd_len++)
  67                 srb->cmnd[srb->cmd_len] = 0;
  68
  69         /* set command length to 12 bytes */
  70         srb->cmd_len = 12;
  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;
 139         struct scatterlist *sg = *sgptr;
 140
 141         /* We have to go through the list one entry
 142          * at a time.  Each s-g entry contains some number of pages, and
 143          * each page has to be kmap()'ed separately.  If the page is already
 144          * in kernel-addressable memory then kmap() will return its address.
 145          * If the page is not directly accessible -- such as a user buffer
 146          * located in high memory -- then kmap() will map it to a temporary
 147          * position in the kernel's virtual address space.
 148          */
 149
 150         if (!sg)
 151                 sg = scsi_sglist(srb);
 152
 153         /* This loop handles a single s-g list entry, which may
 154          * include multiple pages.  Find the initial page structure
 155          * and the starting offset within the page, and update
 156          * the *offset and **sgptr values for the next loop.
 157          */
 158         cnt = 0;
 159         while (cnt < buflen && sg) {
 160                 struct page *page = sg_page(sg) +
 161                                 ((sg->offset + *offset) >> PAGE_SHIFT);
 162                 unsigned int poff = (sg->offset + *offset) & (PAGE_SIZE-1);
 163                 unsigned int sglen = sg->length - *offset;
 164
 165                 if (sglen > buflen - cnt) {
 166
 167                         /* Transfer ends within this s-g entry */
 168                         sglen = buflen - cnt;
 169                         *offset += sglen;
 170                 } else {
 171
 172                         /* Transfer continues to next s-g entry */
 173                         *offset = 0;
 174                         sg = sg_next(sg);
 175                 }
 176
 177                 /* Transfer the data for all the pages in this
 178                         * s-g entry.  For each page: call kmap(), do the
 179                         * transfer, and call kunmap() immediately after. */
 180                 while (sglen > 0) {
 181                         unsigned int plen = min(sglen, (unsigned int)
 182                                         PAGE_SIZE - poff);
 183                         unsigned char *ptr = kmap(page);
 184
 185                         if (dir == TO_XFER_BUF)
 186                                 memcpy(ptr + poff, buffer + cnt, plen);
 187                         else
 188                                 memcpy(buffer + cnt, ptr + poff, plen);
 189                         kunmap(page);
 190
 191                         /* Start at the beginning of the next page */
 192                         poff = 0;
 193                         ++page;
 194                         cnt += plen;
 195                         sglen -= plen;
 196                 }
 197         }
 198         *sgptr = sg;
 199
 200         /* Return the amount actually transferred */
 201         return cnt;
 202 }
 203 EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
 204
 205 /* Store the contents of buffer into srb's transfer buffer and set the
 206  * SCSI residue.
 207  */
 208 void usb_stor_set_xfer_buf(unsigned char *buffer,
 209         unsigned int buflen, struct scsi_cmnd *srb)
 210 {
 211         unsigned int offset = 0;
 212         struct scatterlist *sg = NULL;
 213
 214         buflen = min(buflen, scsi_bufflen(srb));
 215         buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
 216                         TO_XFER_BUF);
 217         if (buflen < scsi_bufflen(srb))
 218                 scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
 219 }
 220 EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);