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 (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
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(cmd: srb);
129
130 if (sg)
131 nents = sg_nents(sg);
132 else
133 sg = scsi_sglist(cmd: srb);
134
135 sg_miter_start(miter: &miter, sgl: sg, nents, flags: dir == FROM_XFER_BUF ?
136 SG_MITER_FROM_SG: SG_MITER_TO_SG);
137
138 if (!sg_miter_skip(miter: &miter, offset: *offset))
139 return cnt;
140
141 while (sg_miter_next(miter: &miter) && cnt < buflen) {
142 unsigned int len = min_t(unsigned int, miter.length,
143 buflen - cnt);
144
145 if (dir == FROM_XFER_BUF)
146 memcpy(to: buffer + cnt, from: miter.addr, len);
147 else
148 memcpy(to: miter.addr, from: buffer + cnt, len);
149
150 if (*offset + len < miter.piter.sg->length) {
151 *offset += len;
152 *sgptr = miter.piter.sg;
153 } else {
154 *offset = 0;
155 *sgptr = sg_next(sg: miter.piter.sg);
156 }
157 cnt += len;
158 }
159 sg_miter_stop(miter: &miter);
160
161 return cnt;
162}
163EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
164
165/*
166 * Store the contents of buffer into srb's transfer buffer and set the
167 * SCSI residue.
168 */
169void usb_stor_set_xfer_buf(unsigned char *buffer,
170 unsigned int buflen, struct scsi_cmnd *srb)
171{
172 unsigned int offset = 0;
173 struct scatterlist *sg = NULL;
174
175 buflen = min(buflen, scsi_bufflen(srb));
176 buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
177 TO_XFER_BUF);
178 if (buflen < scsi_bufflen(cmd: srb))
179 scsi_set_resid(cmd: srb, resid: scsi_bufflen(cmd: srb) - buflen);
180}
181EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);
182