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-S/390 common I/O-Layer - command line parameters, procfs and debugfs entries
-============================================================================
-
-Command line parameters
------------------------
-
-* ccw_timeout_log
-
- Enable logging of debug information in case of ccw device timeouts.
-
-* cio_ignore = {all} |
- {<device> | <range of devices>} |
- {!<device> | !<range of devices>}
-
- The given devices will be ignored by the common I/O-layer; no detection
- and device sensing will be done on any of those devices. The subchannel to
- which the device in question is attached will be treated as if no device was
- attached.
-
- An ignored device can be un-ignored later; see the "/proc entries"-section for
- details.
-
- The devices must be given either as bus ids (0.x.abcd) or as hexadecimal
- device numbers (0xabcd or abcd, for 2.4 backward compatibility). If you
- give a device number 0xabcd, it will be interpreted as 0.0.abcd.
-
- You can use the 'all' keyword to ignore all devices.
- The '!' operator will cause the I/O-layer to _not_ ignore a device.
- The command line is parsed from left to right.
-
- For example,
- cio_ignore=0.0.0023-0.0.0042,0.0.4711
- will ignore all devices ranging from 0.0.0023 to 0.0.0042 and the device
- 0.0.4711, if detected.
- As another example,
- cio_ignore=all,!0.0.4711,!0.0.fd00-0.0.fd02
- will ignore all devices but 0.0.4711, 0.0.fd00, 0.0.fd01, 0.0.fd02.
-
- By default, no devices are ignored.
-
-
-/proc entries
--------------
-
-* /proc/cio_ignore
-
- Lists the ranges of devices (by bus id) which are ignored by common I/O.
-
- You can un-ignore certain or all devices by piping to /proc/cio_ignore.
- "free all" will un-ignore all ignored devices,
- "free <device range>, <device range>, ..." will un-ignore the specified
- devices.
-
- For example, if devices 0.0.0023 to 0.0.0042 and 0.0.4711 are ignored,
- - echo free 0.0.0030-0.0.0032 > /proc/cio_ignore
- will un-ignore devices 0.0.0030 to 0.0.0032 and will leave devices 0.0.0023
- to 0.0.002f, 0.0.0033 to 0.0.0042 and 0.0.4711 ignored;
- - echo free 0.0.0041 > /proc/cio_ignore will furthermore un-ignore device
- 0.0.0041;
- - echo free all > /proc/cio_ignore will un-ignore all remaining ignored
- devices.
-
- When a device is un-ignored, device recognition and sensing is performed and
- the device driver will be notified if possible, so the device will become
- available to the system. Note that un-ignoring is performed asynchronously.
-
- You can also add ranges of devices to be ignored by piping to
- /proc/cio_ignore; "add <device range>, <device range>, ..." will ignore the
- specified devices.
-
- Note: While already known devices can be added to the list of devices to be
- ignored, there will be no effect on then. However, if such a device
- disappears and then reappears, it will then be ignored. To make
- known devices go away, you need the "purge" command (see below).
-
- For example,
- "echo add 0.0.a000-0.0.accc, 0.0.af00-0.0.afff > /proc/cio_ignore"
- will add 0.0.a000-0.0.accc and 0.0.af00-0.0.afff to the list of ignored
- devices.
-
- You can remove already known but now ignored devices via
- "echo purge > /proc/cio_ignore"
- All devices ignored but still registered and not online (= not in use)
- will be deregistered and thus removed from the system.
-
- The devices can be specified either by bus id (0.x.abcd) or, for 2.4 backward
- compatibility, by the device number in hexadecimal (0xabcd or abcd). Device
- numbers given as 0xabcd will be interpreted as 0.0.abcd.
-
-* /proc/cio_settle
-
- A write request to this file is blocked until all queued cio actions are
- handled. This will allow userspace to wait for pending work affecting
- device availability after changing cio_ignore or the hardware configuration.
-
-* For some of the information present in the /proc filesystem in 2.4 (namely,
- /proc/subchannels and /proc/chpids), see driver-model.txt.
- Information formerly in /proc/irq_count is now in /proc/interrupts.
-
-
-debugfs entries
----------------
-
-* /sys/kernel/debug/s390dbf/cio_*/ (S/390 debug feature)
-
- Some views generated by the debug feature to hold various debug outputs.
-
- - /sys/kernel/debug/s390dbf/cio_crw/sprintf
- Messages from the processing of pending channel report words (machine check
- handling).
-
- - /sys/kernel/debug/s390dbf/cio_msg/sprintf
- Various debug messages from the common I/O-layer.
-
- - /sys/kernel/debug/s390dbf/cio_trace/hex_ascii
- Logs the calling of functions in the common I/O-layer and, if applicable,
- which subchannel they were called for, as well as dumps of some data
- structures (like irb in an error case).
-
- The level of logging can be changed to be more or less verbose by piping to
- /sys/kernel/debug/s390dbf/cio_*/level a number between 0 and 6; see the
- documentation on the S/390 debug feature (Documentation/s390/s390dbf.txt)
- for details.