common_io.rst

  1======================
  2S/390 common I/O-Layer
  3======================
  4
  5command line parameters, procfs and debugfs entries
  6===================================================
  7
  8Command line parameters
  9-----------------------
 10
 11* ccw_timeout_log
 12
 13  Enable logging of debug information in case of ccw device timeouts.
 14
 15* cio_ignore = device[,device[,..]]
 16
 17	device := {all | [!]ipldev | [!]condev | [!]<devno> | [!]<devno>-<devno>}
 18
 19  The given devices will be ignored by the common I/O-layer; no detection
 20  and device sensing will be done on any of those devices. The subchannel to
 21  which the device in question is attached will be treated as if no device was
 22  attached.
 23
 24  An ignored device can be un-ignored later; see the "/proc entries"-section for
 25  details.
 26
 27  The devices must be given either as bus ids (0.x.abcd) or as hexadecimal
 28  device numbers (0xabcd or abcd, for 2.4 backward compatibility). If you
 29  give a device number 0xabcd, it will be interpreted as 0.0.abcd.
 30
 31  You can use the 'all' keyword to ignore all devices. The 'ipldev' and 'condev'
 32  keywords can be used to refer to the CCW based boot device and CCW console
 33  device respectively (these are probably useful only when combined with the '!'
 34  operator). The '!' operator will cause the I/O-layer to _not_ ignore a device.
 35  The command line
 36  is parsed from left to right.
 37
 38  For example::
 39
 40	cio_ignore=0.0.0023-0.0.0042,0.0.4711
 41
 42  will ignore all devices ranging from 0.0.0023 to 0.0.0042 and the device
 43  0.0.4711, if detected.
 44
 45  As another example::
 46
 47	cio_ignore=all,!0.0.4711,!0.0.fd00-0.0.fd02
 48
 49  will ignore all devices but 0.0.4711, 0.0.fd00, 0.0.fd01, 0.0.fd02.
 50
 51  By default, no devices are ignored.
 52
 53
 54/proc entries
 55-------------
 56
 57* /proc/cio_ignore
 58
 59  Lists the ranges of devices (by bus id) which are ignored by common I/O.
 60
 61  You can un-ignore certain or all devices by piping to /proc/cio_ignore.
 62  "free all" will un-ignore all ignored devices,
 63  "free <device range>, <device range>, ..." will un-ignore the specified
 64  devices.
 65
 66  For example, if devices 0.0.0023 to 0.0.0042 and 0.0.4711 are ignored,
 67
 68  - echo free 0.0.0030-0.0.0032 > /proc/cio_ignore
 69    will un-ignore devices 0.0.0030 to 0.0.0032 and will leave devices 0.0.0023
 70    to 0.0.002f, 0.0.0033 to 0.0.0042 and 0.0.4711 ignored;
 71  - echo free 0.0.0041 > /proc/cio_ignore will furthermore un-ignore device
 72    0.0.0041;
 73  - echo free all > /proc/cio_ignore will un-ignore all remaining ignored
 74    devices.
 75
 76  When a device is un-ignored, device recognition and sensing is performed and
 77  the device driver will be notified if possible, so the device will become
 78  available to the system. Note that un-ignoring is performed asynchronously.
 79
 80  You can also add ranges of devices to be ignored by piping to
 81  /proc/cio_ignore; "add <device range>, <device range>, ..." will ignore the
 82  specified devices.
 83
 84  Note: While already known devices can be added to the list of devices to be
 85	ignored, there will be no effect on then. However, if such a device
 86	disappears and then reappears, it will then be ignored. To make
 87	known devices go away, you need the "purge" command (see below).
 88
 89  For example::
 90
 91	"echo add 0.0.a000-0.0.accc, 0.0.af00-0.0.afff > /proc/cio_ignore"
 92
 93  will add 0.0.a000-0.0.accc and 0.0.af00-0.0.afff to the list of ignored
 94  devices.
 95
 96  You can remove already known but now ignored devices via::
 97
 98	"echo purge > /proc/cio_ignore"
 99
100  All devices ignored but still registered and not online (= not in use)
101  will be deregistered and thus removed from the system.
102
103  The devices can be specified either by bus id (0.x.abcd) or, for 2.4 backward
104  compatibility, by the device number in hexadecimal (0xabcd or abcd). Device
105  numbers given as 0xabcd will be interpreted as 0.0.abcd.
106
107* /proc/cio_settle
108
109  A write request to this file is blocked until all queued cio actions are
110  handled. This will allow userspace to wait for pending work affecting
111  device availability after changing cio_ignore or the hardware configuration.
112
113* For some of the information present in the /proc filesystem in 2.4 (namely,
114  /proc/subchannels and /proc/chpids), see driver-model.txt.
115  Information formerly in /proc/irq_count is now in /proc/interrupts.
116
117
118debugfs entries
119---------------
120
121* /sys/kernel/debug/s390dbf/cio_*/ (S/390 debug feature)
122
123  Some views generated by the debug feature to hold various debug outputs.
124
125  - /sys/kernel/debug/s390dbf/cio_crw/sprintf
126    Messages from the processing of pending channel report words (machine check
127    handling).
128
129  - /sys/kernel/debug/s390dbf/cio_msg/sprintf
130    Various debug messages from the common I/O-layer.
131
132  - /sys/kernel/debug/s390dbf/cio_trace/hex_ascii
133    Logs the calling of functions in the common I/O-layer and, if applicable,
134    which subchannel they were called for, as well as dumps of some data
135    structures (like irb in an error case).
136
137  The level of logging can be changed to be more or less verbose by piping to
138  /sys/kernel/debug/s390dbf/cio_*/level a number between 0 and 6; see the
139  documentation on the S/390 debug feature (Documentation/arch/s390/s390dbf.rst)
140  for details.