[dpdk-dev] [PATCH v1] eal: add manual probing option

[Gaëtan Rivet]

On Mon, Sep 30, 2019 at 11:53:33AM -0700, Stephen Hemminger wrote:
> On Mon, 30 Sep 2019 14:51:03 +0200
> Gaetan Rivet <gaetan.rivet at 6wind.com> wrote:
> 
> > Add a new EAL option enabling manual probing in the EAL.
> > This command line option will configure the EAL so that buses
> > will not trigger their probe step on their own.
> > 
> > Applications are then expected to hotplug devices as they see fit.
> > 
> > Devices declared on the command line by the user (using -w and --vdev),
> > will be probed using the hotplug API, in the order they are declared.
> > 
> > This has the effect of offering a way for users to control probe order
> > of their devices, for drivers requiring it.
> > 
> > Signed-off-by: Gaetan Rivet <gaetan.rivet at 6wind.com>
> 
> I have no problems with the patch, but it would help if there was better
> way to handle device naming policy in DPDK. Applications that depend on
> particular port number are prone to get broken by changes in surrounding
> OS or hardware environment. Just like Linux applications that are built
> to depend on "eth0"; which is unfortunately all too common.

Hello Stephen,

This patch is a way to avoid having the PCI bus defining the probe order
with the current hardware environment. It seems to be a step in the
right direction for the issue you identify.

There is a tight coupling between device names and driver matches for
the vdev bus, but that seems difficult to avoid.

Do you see other EAL APIs fostering an over reliance of downstream
systems on device names?

I pushed a few months back a way to iterate / match devices by their
properties. If you identify other pain points, this could certainly be
improved as well.

-- 
Gaëtan Rivet
6WIND