Documentation/s390/CommonIO

   1 S/390 common I/O-Layer - command line parameters, procfs and debugfs entries
   2 ============================================================================
   3
   4 Command 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
 103 debugfs 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.