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

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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.)

> 
> 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
> +  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?

But other than that suggestion, everything looks fine.

Reviewed-by: Eric Farman <farman@xxxxxxxxxxxxx>

>  
> @@ -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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