xref: /openbmc/linux/drivers/usb/storage/protocol.c (revision fb960bd2)
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  * Please see http://www.one-eyed-alien.net/~mdharm/linux-usb for more
30  * information about this driver.
31  */
32 
33 #include <linux/highmem.h>
34 #include <linux/export.h>
35 #include <scsi/scsi.h>
36 #include <scsi/scsi_cmnd.h>
37 
38 #include "usb.h"
39 #include "protocol.h"
40 #include "debug.h"
41 #include "scsiglue.h"
42 #include "transport.h"
43 
44 /***********************************************************************
45  * Protocol routines
46  ***********************************************************************/
47 
48 void usb_stor_pad12_command(struct scsi_cmnd *srb, struct us_data *us)
49 {
50 	/*
51 	 * Pad the SCSI command with zeros out to 12 bytes.  If the
52 	 * command already is 12 bytes or longer, leave it alone.
53 	 *
54 	 * NOTE: This only works because a scsi_cmnd struct field contains
55 	 * a unsigned char cmnd[16], so we know we have storage available
56 	 */
57 	for (; srb->cmd_len < 12; srb->cmd_len++)
58 		srb->cmnd[srb->cmd_len] = 0;
59 
60 	/* send the command to the transport layer */
61 	usb_stor_invoke_transport(srb, us);
62 }
63 
64 void usb_stor_ufi_command(struct scsi_cmnd *srb, struct us_data *us)
65 {
66 	/*
67 	 * fix some commands -- this is a form of mode translation
68 	 * UFI devices only accept 12 byte long commands
69 	 *
70 	 * NOTE: This only works because a scsi_cmnd struct field contains
71 	 * a unsigned char cmnd[16], so we know we have storage available
72 	 */
73 
74 	/* Pad the ATAPI command with zeros */
75 	for (; srb->cmd_len < 12; srb->cmd_len++)
76 		srb->cmnd[srb->cmd_len] = 0;
77 
78 	/* set command length to 12 bytes (this affects the transport layer) */
79 	srb->cmd_len = 12;
80 
81 	/* XXX We should be constantly re-evaluating the need for these */
82 
83 	/* determine the correct data length for these commands */
84 	switch (srb->cmnd[0]) {
85 
86 		/* for INQUIRY, UFI devices only ever return 36 bytes */
87 	case INQUIRY:
88 		srb->cmnd[4] = 36;
89 		break;
90 
91 		/* again, for MODE_SENSE_10, we get the minimum (8) */
92 	case MODE_SENSE_10:
93 		srb->cmnd[7] = 0;
94 		srb->cmnd[8] = 8;
95 		break;
96 
97 		/* for REQUEST_SENSE, UFI devices only ever return 18 bytes */
98 	case REQUEST_SENSE:
99 		srb->cmnd[4] = 18;
100 		break;
101 	} /* end switch on cmnd[0] */
102 
103 	/* send the command to the transport layer */
104 	usb_stor_invoke_transport(srb, us);
105 }
106 
107 void usb_stor_transparent_scsi_command(struct scsi_cmnd *srb,
108 				       struct us_data *us)
109 {
110 	/* send the command to the transport layer */
111 	usb_stor_invoke_transport(srb, us);
112 }
113 EXPORT_SYMBOL_GPL(usb_stor_transparent_scsi_command);
114 
115 /***********************************************************************
116  * Scatter-gather transfer buffer access routines
117  ***********************************************************************/
118 
119 /*
120  * Copy a buffer of length buflen to/from the srb's transfer buffer.
121  * Update the **sgptr and *offset variables so that the next copy will
122  * pick up from where this one left off.
123  */
124 unsigned int usb_stor_access_xfer_buf(unsigned char *buffer,
125 	unsigned int buflen, struct scsi_cmnd *srb, struct scatterlist **sgptr,
126 	unsigned int *offset, enum xfer_buf_dir dir)
127 {
128 	unsigned int cnt = 0;
129 	struct scatterlist *sg = *sgptr;
130 	struct sg_mapping_iter miter;
131 	unsigned int nents = scsi_sg_count(srb);
132 
133 	if (sg)
134 		nents = sg_nents(sg);
135 	else
136 		sg = scsi_sglist(srb);
137 
138 	sg_miter_start(&miter, sg, nents, dir == FROM_XFER_BUF ?
139 		SG_MITER_FROM_SG: SG_MITER_TO_SG);
140 
141 	if (!sg_miter_skip(&miter, *offset))
142 		return cnt;
143 
144 	while (sg_miter_next(&miter) && cnt < buflen) {
145 		unsigned int len = min_t(unsigned int, miter.length,
146 				buflen - cnt);
147 
148 		if (dir == FROM_XFER_BUF)
149 			memcpy(buffer + cnt, miter.addr, len);
150 		else
151 			memcpy(miter.addr, buffer + cnt, len);
152 
153 		if (*offset + len < miter.piter.sg->length) {
154 			*offset += len;
155 			*sgptr = miter.piter.sg;
156 		} else {
157 			*offset = 0;
158 			*sgptr = sg_next(miter.piter.sg);
159 		}
160 		cnt += len;
161 	}
162 	sg_miter_stop(&miter);
163 
164 	return cnt;
165 }
166 EXPORT_SYMBOL_GPL(usb_stor_access_xfer_buf);
167 
168 /*
169  * Store the contents of buffer into srb's transfer buffer and set the
170  * SCSI residue.
171  */
172 void usb_stor_set_xfer_buf(unsigned char *buffer,
173 	unsigned int buflen, struct scsi_cmnd *srb)
174 {
175 	unsigned int offset = 0;
176 	struct scatterlist *sg = NULL;
177 
178 	buflen = min(buflen, scsi_bufflen(srb));
179 	buflen = usb_stor_access_xfer_buf(buffer, buflen, srb, &sg, &offset,
180 			TO_XFER_BUF);
181 	if (buflen < scsi_bufflen(srb))
182 		scsi_set_resid(srb, scsi_bufflen(srb) - buflen);
183 }
184 EXPORT_SYMBOL_GPL(usb_stor_set_xfer_buf);
185