Commit 430220b0 authored by Cornelia Huck's avatar Cornelia Huck
Browse files

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: default avatarCornelia Huck <cohuck@redhat.com>
Reviewed-by: default avatarEric Farman <farman@linux.ibm.com>
Message-Id: <20200407111605.1795-1-cohuck@redhat.com>
parent 725b94d7

Documentation/s390/vfio-ccw.rst

+54 −2
Original line number Diff line number Diff line
@@ -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

--------------------------

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