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From: Thomas Monjalon <thomas@monjalon.net>
To: "Tan, Jianfeng" <jianfeng.tan@intel.com>
Cc: dev@dpdk.org
Date: Fri, 01 Dec 2017 09:42:15 +0100
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Subject: Re: [dpdk-dev] [PATCH] bus/vdev: add custom scan hook
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Hi,

01/12/2017 06:48, Tan, Jianfeng:
> Hi Thomas,
> 
> Please help us to understand why we need this.
> 
> 
> On 12/1/2017 8:36 AM, Thomas Monjalon wrote:
> > The scan callback allows to spawn a vdev automatically
> > given some custom scan rules.
> 
> These two new APIs (rte_vdev_add_custom_scan and 
> rte_vdev_remove_custom_scan) are called by applications?

Yes, the application can use it but it can also be used by a DPDK
driver or library.

> If so, why not just constructing them in the parameters before passing 
> to rte_eal_init?

It is not only for initialization because it will also work when
we will have some hotplug mechanism where the scan is run during run-time.

> > It is especially useful to create a TAP device automatically
> > connected to a netdevice as remote.
> 
> It sounds like an use case. Without this patch, I suppose we can already 
> do this?

Yes we can already update the devargs list.
But this hook will help to do it on hotplug events.