1
2 FreeBSD Quirk Guidelines
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4 Nate Lawson - njl at freebsd org
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60. Introduction
7
8FreeBSD drivers make every attempt possible to support the standards
9behind hardware. Where possible and not in conflict with the standard,
10they also attempt to work around hardware which doesn't strictly
11conform. However, some devices have flaws which can't be worked
12around while keeping the driver compatible with the standard. For
13these devices, we have created a quirks mechanism to indicate to
14the driver that it must avoid certain commands or use them differently
15with a specific model and/or version of hardware. This document
16focuses on identifying and committing quirks for storage hardware
17involving CAM and UMASS but is applicable to other areas.
18
19CAM provides a generic transport for SCSI-like devices. Many different
20transports use SCSI command sets including parallel SCSI, firewire
21(1394), USB UMASS, fibre channel, and ATAPI. For block devices (i.e.
22hard drives, flash adapters, cameras) there are two standards, SBC
23and RBC. SCSI hard drives are usually SBC-compliant and smaller
24devices like flash drives are usually RBC-compliant. Multimedia
25devices including CDROMs and DVD-RW are usually MMC-compliant.
26
27Please follow these guidelines to get your device working as soon
28as possible. If you are a committer, please do NOT commit quirks
29directly but follow this process also.
30
311. Determing the problem
32
33The first step is to determine what's wrong. If the device should
34be supported but hangs while attaching, it's possible a quirk can
35help. The types of things a quirk can fix are:
36`
37 * cam/cam_xpt.c quirks
38
39 o CAM_QUIRK_NOLUNS - do not probe luns other than 0 since device
40 responds to all inquiries with "lun present".
41
42 o CAM_QUIRK_NOSERIAL - do not send an inquiry for serial number.
43
44 o CAM_QUIRK_HILUNS - probe all luns even if some respond "not present"
45 since device has a sparse lun space.
46
47 * cam/scsi/scsi_da.c quirks
48
49 o DA_Q_NO_SYNC_CACHE - The sync cache command is used to force a
50 drive to write out all changes to disk before shutting down. Some
51 drives hang when receiving this command even though it is required
52 by all SBC and RBC standards. Note that a warning message on
53 console is NOT sufficient to add this quirk. The warning messages
54 are harmless and only a device or system hang is cause for adding
55 this quirk.
56
57 o DA_Q_NO_6_BYTE - The RBC spec (see Links below) does not allow
58 for 6-byte READ/WRITE commands. Some manufacturers took that too
59 literally and crash when receiving 6-byte commands. This quirk
60 causes FreeBSD to only send 10-byte commands. Since the CAM subsystem
61 has been modified to not send 6-byte commands to USB, 1394, and
62 other transports that don't support SBC, this quirk should be very
63 rare.
64
65 o DA_Q_NO_PREVENT - Don't use the prevent/allow commands to keep a
66 removable medium from being ejected. Some systems can't handle these
67 commands (rare).
68
69 * cam/scsi/scsi_cd.c quirks
70
71 o CD_Q_NO_TOUCH - not implemented
72
73 o CD_Q_BCD_TRACKS - convert start/end track to BCD
74
75 o CD_Q_NO_CHANGER - never treat as a changer
76
77 o CD_Q_CHANGER - always treat as a changer
78
79 * cam/scsi/scsi_ch.c quirks
80 o CH_Q_NO_DBD - disable block descriptors in mode sense
81
82 * cam/scsi/scsi_sa.c quirks
83
84 o SA_QUIRK_NOCOMP - Can't deal with compression at all
85
86 o SA_QUIRK_FIXED - Force fixed mode
87
88 o SA_QUIRK_VARIABLE - Force variable mode
89
90 o SA_QUIRK_2FM - Needs Two File Marks at EOD
91
92 o SA_QUIRK_1FM - No more than 1 File Mark at EOD
93
94 o SA_QUIRK_NODREAD - Don't try and dummy read density
95
96 o SA_QUIRK_NO_MODESEL - Don't do mode select at all
97
98 o SA_QUIRK_NO_CPAGE - Don't use DEVICE COMPRESSION page
99
100 * dev/usb/umass.c quirks
101
102 o NO_TEST_UNIT_READY - The drive does not support Test Unit Ready.
103 Convert to Start Unit. This command is a simple no-op for most
104 firmware but some of them hang when this command is sent.
105
106 o RS_NO_CLEAR_UA - The drive does not reset the Unit Attention state
107 after REQUEST SENSE has been sent. The INQUIRY command does not
108 reset the UA either, and so CAM runs in circles trying to retrieve
109 the initial INQUIRY data. This quirk signifies that after a unit
110 attention condition, don't try to clear the condition with a request
111 sense command.
112
113 o NO_START_STOP - Like test unit ready, don't send this command if it hangs the device.
114
115 o FORCE_SHORT_INQUIRY - Don't ask for full inquiry data (256
116 bytes). Some drives can only handle the shorter inquiry length
117 (36 bytes).
118
119 o SHUTTLE_INIT - Needs to be initialised the Shuttle way. Haven't
120 looked into what this does but apparently it's mostly Shuttle
121 devices.
122
123 o ALT_IFACE_1 - Drive needs to be switched to alternate interface 1. Rare.
124
125 o FLOPPY_SPEED - Drive does not do 1Mb/s, but just floppy speeds (20kb/s).
126
127 o IGNORE_RESIDUE - The device can't count and gets the residue
128 of transfers wrong. This is sometimes needed for devices where
129 large transfers cause stalls.
130
131 o NO_GETMAXLUN - Get maximum LUN is a command to identify multiple
132 devices sharing the same ID. For instance, a multislot compact
133 flash reader might be on two LUNS. Some non-standard devices hang
134 when receiving this command so this quirk disables it.
135
136 o WRONG_CSWSIG - The device uses a weird CSWSIGNATURE. Rare.
137
138 o NO_INQUIRY - Device cannot handle INQUIRY so fake a generic
139 response. INQUIRY is one of the most basic commands but some
140 drives can't even handle it. (No idea how such devices even work
141 at all on other OS's.) This quirk fakes up a valid but generic
142 response for devices that can't handle INQUIRY.
143
144 o NO_INQUIRY_EVPD - Device cannot handle an extended INQUIRY
145 asking for vital product data (EVPD) so just return a "no data"
146 response (check condition) without sending the command to the
147 device.
148
1492. Testing a Quirk
150
151After you have an idea what you want to try, edit the proper file
152above, using wildcarding to be sure your device is matched. Here
153is a list of the common things to try. Note that some devices require
154multiple quirks or quirks in different drivers. For example, some
155USB pen drives or flash readers require quirks in both da(4) and
156umass(4).
157
158* umass(4) device (sys/dev/usb/umass.c) -- this quirk matches an Asahi Optical device with any product ID or revision ID.
159*
160* { USB_VENDOR_ASAHIOPTICAL, PID_WILDCARD, RID_WILDCARD,
161* UMASS_PROTO_ATAPI | UMASS_PROTO_CBI_I,
162* RS_NO_CLEAR_UA
163* },
164* da(4) device (sys/cam/scsi/scsi_da.c) -- this quirk matches a Creative device with a name of "NOMAD_MUVO" and any revision.
165*
166* {
167* /*
168* * Creative Nomad MUVO mp3 player (USB)
169* * PR: kern/53094
170* */
171* {T_DIRECT, SIP_MEDIA_REMOVABLE, "CREATIVE", "NOMAD_MUVO", "*"},
172* /*quirks*/ DA_Q_NO_SYNC_CACHE|DA_Q_NO_PREVENT
173* },
174
1753. Filing a PR
176
177All quirk submissions MUST go through GNATS. For information on how
178to submit a PR, see this page.
179
180Please include the following in your PR:
181
182 * Subject: QUIRK: FooCo USB DVD-RAM drive
183 * Output of "camcontrol inquiry yourdevice"
184 * Manufacturer name, model number, etc.
185 * Transport type (FC, SCSI, USB, Firewire)
186 * Output from dmesg for failed attach attempts
187 * Output from dmesg for successful attach attempts (after quirk added)
188 * Output of "usbdevs -v" with device attached
189 * Valid email address
190
191Here are some examples of well-formed PRs:
192
193 * kern/43580
194 * kern/49054
195
1964. What happens next
197
198I will review your submission, respond with comments, and once the
199quirk is deemed necessary and ready for committing, I'll commit it,
200referencing the PR. (Again, all quirks must be submitted as PRs).
201Questions? Email njl AT freebsd.org.
202
2035. Note to Committers
204
205Please insert quirks in the right section in scsi_da.c, sorted by
206PR number. Always include the name and PR number for scsi_da.c (see
207above for an example.) Please sort quirks alphabetically in umass.c.
208Follow the surrounding style in all drivers. Be sure to correspond
209with the submitter to be sure the quirk you are adding is the minimum
210necessary, not quirking other useful features and not overly broad
211(i.e., too many wildcards).
212