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