[dpdk-dev] [PATCH] bus/vdev: add custom scan hook

[Tan, Jianfeng]

 > From: Thomas Monjalon [mailto:thomas at monjalon.net]
 > Sent: Tuesday, December 5, 2017 11:21 PM
 > To: Tan, Jianfeng
 > Cc: dev at dpdk.org
 > Subject: Re: [PATCH] bus/vdev: add custom scan hook
 >
 > 05/12/2017 14:56, Tan, Jianfeng:
 > >
 > > On 12/5/2017 4:41 PM, Thomas Monjalon wrote:
 > > >
 > > > 05/12/2017 09:27, Tan, Jianfeng:
 > > >
 > > > >
 > > >
 > > > > On 12/4/2017 5:31 PM, Thomas Monjalon wrote:
 > > >
 > > > > >
 > > >
 > > > > > The hook is in bus->scan().
 > > >
 > > > > > I think we should launch a bus scan when there is a new 
device event.
 > > >
 > > > >
 > > >
 > > > > That's what I'm trying to say. We finally need to execute a 
handler as
 > > >
 > > > > of a device event to finish the job.
 > > >
 > > > Please be more specific, I am not sure to understand.
 > > >
 > >
 > > By the handler, I mean when we monitor the udev by 
select/poll/epoll and
 > > device uevents come, the application will execute a handler (or just a
 > > function) for each of such uevent. Then why not adding the vdev there?
 >
 > Because it must work for hotplug, and initial scan too.
 > We can also think to application requiring a manual scan.
 > The bus scan is the right place to have every scans called. That's 
simple.

Yes, the logic is simpler; anything changes, appication just invokes a 
scan.Then we will have a somewhat complex hook that: (1) scan all 
devices and identify added/removed devices; (2) and add vdev for added 
device; (3) remove vdev for removed device.

Compared to that, we can separate the implementation for hotplug and 
initial scan:
   * For initial scan, iterate all devices to add vdev for each of them.
   * For hotplug, based on which device is added/removed, we just 
add/remove the corresponding vdev for that device.

Anyway, since this patch does provide a new way; and will not affect the 
other way. So I think it's OK to add this.

Thank you for your clarification.

Thanks,
Jianfeng