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