Re: [PATCH v1 2/2] transport-pci: Move transitional device id to legacy section

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Feb 27, 2023 at 02:54:09AM +0000, Parav Pandit wrote:
> 
> 
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Saturday, February 25, 2023 6:00 PM
> > 
> > On Sun, Feb 26, 2023 at 12:06:36AM +0200, Parav Pandit wrote:
> > > Currently PCI device requirements section contains mix of normative
> > > statements for for regular (non transitional) device and transitional
> > > device under one section.
> > >
> > > Some requirements of the transitional device are also located in
> > > legacy interface section which is the right section for it.
> > >
> > > Hence,
> > > 1. Move transitional device requirements to their designated Legacy
> > >    interface section
> > > 2. Describe regular device requirements without quoting it as "non
> > >    transitional device"
> > >
> > > While at it, write the description using a singular object definition.
> > >
> > > This is only an editorial change.
> > >
> > > This patch is on top of [1].
> > >
> > > [1]
> > > https://lists.oasis-open.org/archives/virtio-dev/202302/msg00578.html
> > >
> > > Signed-off-by: Parav Pandit <parav@nvidia.com>
> > 
> > nack I already answered this. legacy sections describe legacy interface of
> > transitional devices.
> > 
> Legacy device id of the transitional device is 0x1000 for net. 
> Legacy revision id of the transitional device is 0x0.
> Why revision id belongs to legacy section, but device id doesn't?
> Still trying to understand this convoluted policy.
> Will re-read your email again if that is explained somehow without bringing the driver in context.

It's convoluted because legacy is convoluted. It's a bolt-on.
We have a modern description. Is says e.g. "A".
Then legacy chapter comes and say "yea but legacy is B".
This is not how spec normally works.


The rule is this: one should be able to ignore legacy
sections if not building a legacy driver/device.

If you are building a modern driver it must support transitional
devices. Thus is must know about id 0x1000.
Conclusion - 0x1000 is out of legacy section.


If you are building a modern driver it ignores revision.
But legacy drivers used revision 0.
So a transitional device has 0 to make legacy drivers work.
Conclusion - revision 0 is in the legacy section.






-- 
MST