Re: [yang-doctors] A compact way to compare a type in YANG

[Martin Björklund <[e-mail]>]

Hi,

Scott Mansfield <scott.mansfield=[e-mail]> wrote:
> Yang Doctors,
> 
>  
> 
> The IEEE has been working on the IEEE 802.1 bridge model and while updating
> some when statements in  YANG models ieee802-dot1q-bridge and
> ieee802-dot1q-pb to select conditions for certain types of bridge components
> we had a question. 
> 
>  
> 
> The pertinent part of the bridge tree is this:
> 
>  
> 
> module: ieee802-dot1q-bridge
> 
>   +--rw bridges
> 
>      +--rw bridge* [name]
> 
>         +--rw name           dot1qtypes:name-type
> 
>         +--rw address        ieee:mac-address
> 
>         +--rw bridge-type    identityref
> 
>         +--ro ports?         uint16
> 
>         +--ro up-time?       yang:zero-based-counter32
> 
>         +--ro components?    uint32
> 
>         +--rw component* [name]
> 
>            +--rw name                     string
> 
>            +--rw id?                      uint32
> 
>            +--rw type                     identityref <- This is the type we
> want to test.
> 
>            +--rw address?                 ieee:mac-address
> 
>  
> 
>  
> 
>  
> 
> And later in the same file an augmented interface tree looks like  this:
> 
>  
> 
>  
> 
> augment /if:interfaces/if:interface:
> 
>     +--rw bridge-port
> 
>        +--rw bridge-name?                           -> /bridges/bridge/name
> 
>        +--rw component-name?                        ->
> /bridges/bridge[dot1q:name=current()/../bridge-name]/component/name
> 
>  
> 
>  
> 
> In several places we are using a when statement with an xpath condition
> while in the interface tree context: (This is what it looks like in the
> ieee802-dot1q-pb module)
> 
> when
> 
>  
> "/dot1q:bridges/dot1q:bridge[dot1q:name=current()/../dot1q:bridge-name]/dot1
> q:component[dot1q:name=current()/../dot1q:component-name]/dot1q:type =
> 'dot1q:c-vlan-component'
> 
>  
> 
> We had a discussion on our Yangsters meeting this seem rather cumbersome and
> whether the component type value could be locally instantiated with the
> value of the respective component type to reduce the when statement to: 
> 
>  
> 
> when " ../dot1q:component-type = 'dot1q:c-vlan-component' "
> 
>  
> 
> The suggestion was adding this:
> 
>  
> 
>       leaf component-type {
> 
>         type leafref {
> 
>           path
> "/dot1q:bridges/dot1q:bridge[dot1q:name=current()/../bridge-name]/dot1q:comp
> onent[dot1q:name=current()/../component-name]/dot1q:type";  
> 
>         }
> 
>         description
> 
>           "Used to reference the Component type.";
> 
>       }
> 
>  
> 
> However I don't think this works it seems to only make the leafref type of
> component-type the same as the dot1q type of ../component/type which is an
> identityref. (type-of-component) . Other attempts to make this work failed
> too.

This works, but it requires the operator to explicitly set this leaf,
which probably is not what you want.



> Does YANG offer another mechanism for a more compact form to do what we
> want? 

Not that I can think of.


/martin


> 
>  
> 
> Thanks for your consideration!
> 
>  
> 
> Regards,
> 
> -scott.
> 
>  
>