Re: [PATCH] vfio-ccw: document possible errors

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On 5/8/20 6:55 AM, Cornelia Huck wrote:
> On Fri, 17 Apr 2020 12:33:18 -0400
> Eric Farman <farman@xxxxxxxxxxxxx> wrote:
> 
>> On 4/7/20 7:16 AM, Cornelia Huck wrote:
>>> 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.  
>>
>> (Makes a note to myself, to do the same for the schib/crw regions we're
>> adding for channel path handling.)
> 
> Yes, please :) I plan to merge this today, so you can add a patch on
> top.

I finally picked this up and realized that the io and async regions both
document the return codes that would be stored in a field within their
respective regions. The schib/crw regions don't have any such field, so
the only values to be documented are the ones that the .read callback
itself returns. What obvious thing am I missing?

> 
>>
>>>
>>> Signed-off-by: Cornelia Huck <cohuck@xxxxxxxxxx>
>>> ---
>>>  Documentation/s390/vfio-ccw.rst | 54 ++++++++++++++++++++++++++++++++-
>>>  1 file changed, 53 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/s390/vfio-ccw.rst b/Documentation/s390/vfio-ccw.rst
>>> index fca9c4f5bd9c..4538215a362c 100644
>>> --- a/Documentation/s390/vfio-ccw.rst
>>> +++ b/Documentation/s390/vfio-ccw.rst
>>> @@ -210,7 +210,36 @@ 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, did not
>>> +  specify prefetch mode, or the scsw specified a function other than the
> 
> 'did not specify prefetch mode' needs to be dropped now, will do so
> before queuing.
> 
>>> +  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.  
>>
>> Maybe move this little line up between the struct layout and "While
>> starting an I/O request, orb_area ..." instead of being lost way down here?
> 
> Good idea, that also would match the documentation for the async region.
> 
>>
>> But other than that suggestion, everything looks fine.
>>
>> Reviewed-by: Eric Farman <farman@xxxxxxxxxxxxx>
> 
> Thanks!
> 
>>
>>>  
>>> @@ -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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