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  * (Note: for scatter-gather transfers (srb->use_sg > 0), srb->request_buffer
 153  * points to a list of s-g entries and we ignore srb->request_bufflen.
 154  * For non-scatter-gather transfers, srb->request_buffer points to the
 155  * transfer buffer itself and srb->request_bufflen is the buffer's length.)
 156  * Update the *index and *offset variables so that the next copy will
 157  * pick up from where this one left off. */
 158
 159 unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
 160         unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
 161         unsigned int *offset, enum xfer_buf_dir dir)
 162 {
 163         unsigned int cnt;
 164
 165         /* If not using scatter-gather, just transfer the data directly.
 166          * Make certain it will fit in the available buffer space. */
 167         if (srb->use_sg == 0) {
 168                 if (*offset >= srb->request_bufflen)
 169                         return 0;
 170                 cnt = min(buflen, srb->request_bufflen - *offset);
 171                 if (dir == TO_XFER_BUF)
 172                         memcpy((unsigned char *) srb->request_buffer + *offset,
 173                                         buffer, cnt);
 174                 else
 175                         memcpy(buffer, (unsigned char *) srb->request_buffer +
 176                                         *offset, cnt);
 177                 *offset += cnt;
 178
 179         /* Using scatter-gather.  We have to go through the list one entry
 180          * at a time.  Each s-g entry contains some number of pages, and
 181          * each page has to be kmap()'ed separately.  If the page is already
 182          * in kernel-addressable memory then kmap() will return its address.
 183          * If the page is not directly accessible -- such as a user buffer
 184          * located in high memory -- then kmap() will map it to a temporary
 185          * position in the kernel's virtual address space. */
 186         } else {
 187                 struct scatterlist *sg = *sgptr;
 188
 189                 if (!sg)
 190                         sg = (struct scatterlist *) srb->request_buffer;
 191
 192                 /* This loop handles a single s-g list entry, which may
 193                  * include multiple pages.  Find the initial page structure
 194                  * and the starting offset within the page, and update
 195                  * the *offset and *index values for the next loop. */
 196                 cnt = 0;
 197                 while (cnt < buflen) {
 198                         struct page *page = sg_page(sg) +
 199                                         ((sg->offset + *offset) >> PAGE_SHIFT);
 200                         unsigned int poff =
 201                                         (sg->offset + *offset) & (PAGE_SIZE-1);
 202                         unsigned int sglen = sg->length - *offset;
 203
 204                         if (sglen > buflen - cnt) {
 205
 206                                 /* Transfer ends within this s-g entry */
 207                                 sglen = buflen - cnt;
 208                                 *offset += sglen;
 209                         } else {
 210
 211                                 /* Transfer continues to next s-g entry */
 212                                 *offset = 0;
 213                                 sg = sg_next(sg);
 214                         }
 215
 216                         /* Transfer the data for all the pages in this
 217                          * s-g entry.  For each page: call kmap(), do the
 218                          * transfer, and call kunmap() immediately after. */
 219                         while (sglen > 0) {
 220                                 unsigned int plen = min(sglen, (unsigned int)
 221                                                 PAGE_SIZE - poff);
 222                                 unsigned char *ptr = kmap(page);
 223
 224                                 if (dir == TO_XFER_BUF)
 225                                         memcpy(ptr + poff, buffer + cnt, plen);
 226                                 else
 227                                         memcpy(buffer + cnt, ptr + poff, plen);
 228                                 kunmap(page);
 229
 230                                 /* Start at the beginning of the next page */
 231                                 poff = 0;
 232                                 ++page;
 233                                 cnt += plen;
 234                                 sglen -= plen;
 235                         }
 236                 }
 237                 *sgptr = sg;
 238         }
 239
 240         /* Return the amount actually transferred */
 241         return cnt;
 242 }
 243
 244 /* Store the contents of buffer into srb's transfer buffer and set the
 245  * SCSI residue. */
 246 void usb_stor_set_xfer_buf(unsigned char *buffer,
 247         unsigned int buflen, struct scsi_cmnd *srb)
 248 {
 249         unsigned int offset = 0;
 250         struct scatterlist *sg = NULL;
 251
 252         usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
 253                         TO_XFER_BUF);
 254         if (buflen < srb->request_bufflen)
 255                 srb->resid = srb->request_bufflen - buflen;
 256 }