Messages in this thread | | | Subject | Re: [PATCH V2 3/5] vDPA: introduce vDPA bus | From | Jason Wang <> | Date | Thu, 13 Feb 2020 22:58:44 +0800 |
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On 2020/2/13 下午9:41, Jason Gunthorpe wrote: > On Thu, Feb 13, 2020 at 11:34:10AM +0800, Jason Wang wrote: > >>> You have dev, type or >>> class to choose from. Type is rarely used and doesn't seem to be used >>> by vdpa, so class seems the right choice >>> >>> Jason >> Yes, but my understanding is class and bus are mutually exclusive. So we >> can't add a class to a device which is already attached on a bus. > While I suppose there are variations, typically 'class' devices are > user facing things and 'bus' devices are internal facing (ie like a > PCI device)
Though all vDPA devices have the same programming interface, but the semantic is different. So it looks to me that use bus complies what class.rst said:
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Each device class defines a set of semantics and a programming interface that devices of that class adhere to. Device drivers are the implementation of that programming interface for a particular device on a particular bus.
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> > So why is this using a bus? VDPA is a user facing object, so the > driver should create a class vhost_vdpa device directly, and that > driver should live in the drivers/vhost/ directory.
This is because we want vDPA to be generic for being used by different drivers which is not limited to vhost-vdpa. E.g in this series, it allows vDPA to be used by kernel virtio drivers. And in the future, we will probably introduce more drivers in the future.
> > For the PCI VF case this driver would bind to a PCI device like > everything else > > For our future SF/ADI cases the driver would bind to some > SF/ADI/whatever device on a bus.
All these driver will still be bound to their own bus (PCI or other). And what the driver needs is to present a vDPA device to virtual vDPA bus on top.
Thanks
> > I don't see a reason for VDPA to be creating busses.. > > Jason >
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