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 
usb_stor_pad12_command(struct scsi_cmnd * srb,struct us_data * us)45 void 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 
usb_stor_ufi_command(struct scsi_cmnd * srb,struct us_data * us)61 void 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 
usb_stor_transparent_scsi_command(struct scsi_cmnd * srb,struct us_data * us)104 void 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 }
110 EXPORT_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  */
usb_stor_access_xfer_buf(unsigned char * buffer,unsigned int buflen,struct scsi_cmnd * srb,struct scatterlist ** sgptr,unsigned int * offset,enum xfer_buf_dir dir)121 unsigned 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_t(unsigned int, miter.length,
143 				buflen - cnt);
144 
145 		if (dir == FROM_XFER_BUF)
146 			memcpy(buffer + cnt, miter.addr, len);
147 		else
148 			memcpy(miter.addr, 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(miter.piter.sg);
156 		}
157 		cnt += len;
158 	}
159 	sg_miter_stop(&miter);
160 
161 	return cnt;
162 }
163 EXPORT_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  */
usb_stor_set_xfer_buf(unsigned char * buffer,unsigned int buflen,struct scsi_cmnd * srb)169 void 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(srb))
179 		scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
180 }
181 EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);
182