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s390/docs: mention subchannel types

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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>
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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 channel I/O mechanism described here, there are various other methods
(like the diag interface). These are out of the scope of this document. (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 Some additional information can also be found in the kernel source under
Documentation/s390/driver-model.txt. 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 The ccw bus
=========== ===========