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s390/docs: mention subchannel types 

Since the original inception of the s390-drivers document, the
common I/O layer has grown support for more types of subchannels.
Give at least a pointer for the various types.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
pull/30/head
Cornelia Huck 2017-07-11 15:44:09 +02:00 committed by Martin Schwidefsky
parent f3ea8419b9
commit 7ddd091341
1 changed files with 19 additions and 0 deletions
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19
Documentation/driver-api/s390-drivers.rst
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@ -22,9 +22,28 @@ While most I/O devices on a s390 system are typically driven through the
channel I/O mechanism described here, there are various other methods
(like the diag interface). These are out of the scope of this document.
The s390 common I/O layer also provides access to some devices that are
not strictly considered I/O devices. They are considered here as well,
although they are not the focus of this document.
Some additional information can also be found in the kernel source under
Documentation/s390/driver-model.txt.
The css bus
===========
The css bus contains the subchannels available on the system. They fall
into several categories:
* Standard I/O subchannels, for use by the system. They have a child
device on the ccw bus and are described below.
* I/O subchannels bound to the vfio-ccw driver. See
Documentation/s390/vfio-ccw.txt.
* Message subchannels. No Linux driver currently exists.
* CHSC subchannels (at most one). The chsc subchannel driver can be used
to send asynchronous chsc commands.
* eADM subchannels. Used for talking to storage class memory.
The ccw bus
===========