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diff --git a/Documentation/s390/common_io.rst b/Documentation/s390/common_io.rst new file mode 100644 index 000000000000..846485681ce7 --- /dev/null +++ b/Documentation/s390/common_io.rst @@ -0,0 +1,140 @@ +====================== +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 = device[,device[,..]] + + device := {all | [!]ipldev | [!]condev | [!]<devno> | [!]<devno>-<devno>} + + 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 'ipldev' and 'condev' + keywords can be used to refer to the CCW based boot device and CCW console + device respectively (these are probably useful only when combined with the '!' + operator). 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.rst) + for details. |