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vfio-ccw: document possible errors 

Interacting with the I/O and the async regions can yield a number
of errors, which had been undocumented so far. These are part of
the api, so remedy that.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Message-Id: <20200407111605.1795-1-cohuck@redhat.com>
This commit is contained in:
Cornelia Huck 2020-04-07 13:16:05 +02:00
parent 725b94d741
commit 430220b0bb
1 changed files with 54 additions and 2 deletions
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56
Documentation/s390/vfio-ccw.rst
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@ -204,15 +204,44 @@ definition of the region is::
__u32 ret_code;
} __packed;
This region is always available.
While starting an I/O request, orb_area should be filled with the
guest ORB, and scsw_area should be filled with the SCSW of the Virtual
Subchannel.
irb_area stores the I/O result.
ret_code stores a return code for each access of the region.
ret_code stores a return code for each access of the region. The following
values may occur:
``0``
The operation was successful.
``-EOPNOTSUPP``
The orb specified transport mode or an unidentified IDAW format, or the
scsw specified a function other than the start function.
``-EIO``
A request was issued while the device was not in a state ready to accept
requests, or an internal error occurred.
``-EBUSY``
The subchannel was status pending or busy, or a request is already active.
``-EAGAIN``
A request was being processed, and the caller should retry.
``-EACCES``
The channel path(s) used for the I/O were found to be not operational.
``-ENODEV``
The device was found to be not operational.
``-EINVAL``
The orb specified a chain longer than 255 ccws, or an internal error
occurred.
This region is always available.
vfio-ccw cmd region
-------------------
@ -231,6 +260,29 @@ This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD.
Currently, CLEAR SUBCHANNEL and HALT SUBCHANNEL use this region.
command specifies the command to be issued; ret_code stores a return code
for each access of the region. The following values may occur:
``0``
The operation was successful.
``-ENODEV``
The device was found to be not operational.
``-EINVAL``
A command other than halt or clear was specified.
``-EIO``
A request was issued while the device was not in a state ready to accept
requests.
``-EAGAIN``
A request was being processed, and the caller should retry.
``-EBUSY``
The subchannel was status pending or busy while processing a halt request.
vfio-ccw operation details
--------------------------