Re: [Qemu-devel] [PATCH v8 4/6] docs: Add Documentation for Mediated devices

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 12 Oct 2016 20:43:48 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 10/12/2016 7:22 AM, Tian, Kevin wrote:
> >> From: Kirti Wankhede [mailto:kwankhede@nvidia.com]
> >> Sent: Wednesday, October 12, 2016 4:45 AM  
> >>>> +* mdev_supported_types:
> >>>> +    List of current supported mediated device types and its details are added
> >>>> +in this directory in following format:
> >>>> +
> >>>> +|- <parent phy device>
> >>>> +|--- Vendor-specific-attributes [optional]
> >>>> +|--- mdev_supported_types
> >>>> +|     |--- <type id>
> >>>> +|     |   |--- create
> >>>> +|     |   |--- name
> >>>> +|     |   |--- available_instances
> >>>> +|     |   |--- description /class
> >>>> +|     |   |--- [devices]
> >>>> +|     |--- <type id>
> >>>> +|     |   |--- create
> >>>> +|     |   |--- name
> >>>> +|     |   |--- available_instances
> >>>> +|     |   |--- description /class
> >>>> +|     |   |--- [devices]
> >>>> +|     |--- <type id>
> >>>> +|          |--- create
> >>>> +|          |--- name
> >>>> +|          |--- available_instances
> >>>> +|          |--- description /class
> >>>> +|          |--- [devices]
> >>>> +
> >>>> +[TBD : description or class is yet to be decided. This will change.]  
> >>>
> >>> I thought that in previous discussions we had agreed to drop
> >>> the <type id> concept and use the name as the unique identifier.
> >>> When reporting these types in libvirt we won't want to report
> >>> the type id values - we'll want the name strings to be unique.
> >>>  
> >>
> >> The 'name' might not be unique but type_id will be. For example that Neo
> >> pointed out in earlier discussion, virtual devices can come from two
> >> different physical devices, end user would be presented with what they
> >> had selected but there will be internal implementation differences. In
> >> that case 'type_id' will be unique.
> >>  
> > 
> > Hi, Kirti, my understanding is that Neo agreed to use an unique type
> > string (if you still called it <type id>), and then no need of additional
> > 'name' field which can be put inside 'description' field. See below quote:
> >   
> 
> We had internal discussions about this within NVIDIA and found that
> 'name' might not be unique where as 'type_id' would be unique. I'm
> refering to Neo's mail after that, where Neo do pointed that out.
> 
> https://lists.gnu.org/archive/html/qemu-devel/2016-09/msg07714.html

Everyone not privy to those internal discussions, including me, seems to
think we dropped type_id and that if a vendor does not have a stable
name, they can compose some sort of stable type description based on the
name+id, or even vendor+id, ex. NVIDIA-11.  So please share why we
haven't managed to kill off type_id yet.  No matter what internal
representation each vendor driver has of "type_id" it seems possible
for it to come up with stable string to define a given configuration.
Thanks,

Alex