Channel subsystem view

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest KVM guest

The channel subsystem view shows the relationship between subchannels and devices.

The channel subsystem view is of the form:

/sys/devices/css0/<subchannel>

where:

<subchannel>: is a subchannel number with a leading 0.<n>., where <n> is the subchannel set ID.

I/O subchannels show the devices in relation to their respective subchannel sets and subchannels. An I/O subchannel is of the form:

/sys/devices/css0/<subchannel>/<device_bus_id>

where:

<subchannel>: is a subchannel number with a leading 0.<n>., where <n> is the subchannel set ID.
<device_bus_id>: is a device number with a leading 0.<n>., where <n> is the subchannel set ID.

Examples

This example shows a CCW device with device number 0xb100 that is associated with a subchannel 0x0001.
```
/sys/devices/css0/0.0.0001/0.0.b100
```
This example shows a CCW device with device number 0xb200 that is associated with a subchannel 0x0001 in subchannel set 1.
```
/sys/devices/css0/0.1.0001/0.1.b200
```
The entries for a group device show as separate subchannels. If a CCW group device uses three subchannels 0x0002, 0x0003, and 0x0004 the subchannel information could be:
```
/sys/devices/css0/0.0.0002/0.0.a100
/sys/devices/css0/0.0.0003/0.0.a101
/sys/devices/css0/0.0.0004/0.0.a102
```
Each subchannel is associated with a device number. Only the primary device number is used for the bus ID of the device in the device driver view and the device view.
This example lists the information available for a non-I/O subchannel with which no device is associated:
```
ls /sys/devices/css0/0.0.ff00/
bus  driver  modalias  subsystem  type  uevent
```