From: Jason Wang <jasowang@xxxxxxxxxx>
Sent: Monday, November 18, 2019 10:08 PM
On 2019/11/16 上午7:25, Parav Pandit wrote:
Hi Jeff,
From: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
Sent: Friday, November 15, 2019 4:34 PM
From: Dave Ertman <david.m.ertman@xxxxxxxxx>
This is the initial implementation of the Virtual Bus, virtbus_device
and virtbus_driver. The virtual bus is a software based bus intended
to support lightweight devices and drivers and provide matching
between them and probing of the registered drivers.
The primary purpose of the virual bus is to provide matching services
and to pass the data pointer contained in the virtbus_device to the
virtbus_driver during its probe call. This will allow two separate
kernel objects to match up and start communication.
It is fundamental to know that rdma device created by virtbus_driver will be
anchored to which bus for an non abusive use.
virtbus or parent pci bus?
I asked this question in v1 version of this patch.
Also since it says - 'to support lightweight devices', documenting that
information is critical to avoid ambiguity.
Since for a while I am working on the subbus/subdev_bus/xbus/mdev [1]
whatever we want to call it, it overlaps with your comment about 'to support
lightweight devices'.
Hence let's make things crystal clear weather the purpose is 'only matching
service' or also 'lightweight devices'.
If this is only matching service, lets please remove lightweight devices part..
Yes, if it's matching + lightweight device, its function is almost a duplication of
mdev. And I'm working on extending mdev[1] to be a generic module to
support any types of virtual devices a while. The advantage of mdev is:
1) ready for the userspace driver (VFIO based)
2) have a sysfs/GUID based management interface
So for 1, it's not clear that how userspace driver would be supported here, or
it's completely not being accounted in this series? For 2, it looks to me that this
series leave it to the implementation, this means management to learn several
vendor specific interfaces which seems a burden.
Note, technically Virtual Bus could be implemented on top of [1] with the full
lifecycle API.
[1] https://lkml.org/lkml/2019/11/18/261
You additionally need modpost support for id table integration to modifo,
modprobe and other tools.
A small patch similar to this one [2] is needed.
Please include in the series.
[..]
And probably a uevent method. But rethinking of this, matching through a
single virtual bus seems not good. What if driver want to do some specific
matching? E.g for virtio, we may want a vhost-net driver that only match
networking device. With a single bus, it probably means you need another bus
on top and provide the virtio specific matching there.
This looks not straightforward as allowing multiple type of buses.
