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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Driver for USB Mass Storage compliant devices
4 *
5 * Current development and maintenance by:
6 * (c) 1999-2002 Matthew Dharm ([email protected])
7 *
8 * Developed with the assistance of:
9 * (c) 2000 David L. Brown, Jr. ([email protected])
10 * (c) 2002 Alan Stern ([email protected])
11 *
12 * Initial work by:
13 * (c) 1999 Michael Gee ([email protected])
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
30#include <linux/highmem.h>
31#include <linux/export.h>
32#include <scsi/scsi.h>
33#include <scsi/scsi_cmnd.h>
34
35#include "usb.h"
36#include "protocol.h"
37#include "debug.h"
38#include "scsiglue.h"
39#include "transport.h"
40
41/***********************************************************************
42 * Protocol routines
43 ***********************************************************************/
44
45void usb_stor_pad12_command(struct scsi_cmnd *srb, struct us_data *us)
46{
47 /*
48 * Pad the SCSI command with zeros out to 12 bytes. If the
49 * command already is 12 bytes or longer, leave it alone.
50 *
51 * NOTE: This only works because a scsi_cmnd struct field contains
52 * a unsigned char cmnd[16], so we know we have storage available
53 */
54 for (; srb->cmd_len < 12; srb->cmd_len++)
55 srb->cmnd[srb->cmd_len] = 0;
56
57 /* send the command to the transport layer */
58 usb_stor_invoke_transport(srb, us);
59}
60
61void usb_stor_ufi_command(struct scsi_cmnd *srb, struct us_data *us)
62{
63 /*
64 * fix some commands -- this is a form of mode translation
65 * UFI devices only accept 12 byte long commands
66 *
67 * NOTE: This only works because a scsi_cmnd struct field contains
68 * a unsigned char cmnd[16], so we know we have storage available
69 */
70
71 /* Pad the ATAPI command with zeros */
72 for (; srb->cmd_len < 12; srb->cmd_len++)
73 srb->cmnd[srb->cmd_len] = 0;
74
75 /* set command length to 12 bytes (this affects the transport layer) */
76 srb->cmd_len = 12;
77
78 /* XXX We should be constantly re-evaluating the need for these */
79
80 /* determine the correct data length for these commands */
81 switch (srb->cmnd[0]) {
82
83 /* for INQUIRY, UFI devices only ever return 36 bytes */
84 case INQUIRY:
85 srb->cmnd[4] = 36;
86 break;
87
88 /* again, for MODE_SENSE_10, we get the minimum (8) */
89 case MODE_SENSE_10:
90 srb->cmnd[7] = 0;
91 srb->cmnd[8] = 8;
92 break;
93
94 /* for REQUEST_SENSE, UFI devices only ever return 18 bytes */
95 case REQUEST_SENSE:
96 srb->cmnd[4] = 18;
97 break;
98 } /* end switch on cmnd[0] */
99
100 /* send the command to the transport layer */
101 usb_stor_invoke_transport(srb, us);
102}
103
104void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
105 struct us_data *us)
106{
107 /* send the command to the transport layer */
108 usb_stor_invoke_transport(srb, us);
109}
110EXPORT_SYMBOL_GPL(usb_stor_transparent_scsi_command);
111
112/***********************************************************************
113 * Scatter-gather transfer buffer access routines
114 ***********************************************************************/
115
116/*
117 * Copy a buffer of length buflen to/from the srb's transfer buffer.
118 * Update the **sgptr and *offset variables so that the next copy will
119 * pick up from where this one left off.
120 */
121unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
122 unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
123 unsigned int *offset, enum xfer_buf_dir dir)
124{
125 unsigned int cnt = 0;
126 struct scatterlist *sg = *sgptr;
127 struct sg_mapping_iter miter;
128 unsigned int nents = scsi_sg_count(srb);
129
130 if (sg)
131 nents = sg_nents(sg);
132 else
133 sg = scsi_sglist(srb);
134
135 sg_miter_start(&miter, sg, nents, dir == FROM_XFER_BUF ?
136 SG_MITER_FROM_SG: SG_MITER_TO_SG);
137
138 if (!sg_miter_skip(&miter, *offset))
139 return cnt;
140
141 while (sg_miter_next(&miter) && cnt < buflen) {
142 unsigned int len = min(miter.length, buflen - cnt);
143
144 if (dir == FROM_XFER_BUF)
145 memcpy(buffer + cnt, miter.addr, len);
146 else
147 memcpy(miter.addr, buffer + cnt, len);
148
149 if (*offset + len < miter.piter.sg->length) {
150 *offset += len;
151 *sgptr = miter.piter.sg;
152 } else {
153 *offset = 0;
154 *sgptr = sg_next(miter.piter.sg);
155 }
156 cnt += len;
157 }
158 sg_miter_stop(&miter);
159
160 return cnt;
161}
162EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
163
164/*
165 * Store the contents of buffer into srb's transfer buffer and set the
166 * SCSI residue.
167 */
168void usb_stor_set_xfer_buf(unsigned char *buffer,
169 unsigned int buflen, struct scsi_cmnd *srb)
170{
171 unsigned int offset = 0;
172 struct scatterlist *sg = NULL;
173
174 buflen = min(buflen, scsi_bufflen(srb));
175 buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
176 TO_XFER_BUF);
177 if (buflen < scsi_bufflen(srb))
178 scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
179}
180EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);