[dpdk-dev] [PATCH] app/testpmd: change port detach interface

[Nithin Dabilpuram]

On Wed, May 15, 2019 at 09:27:22AM +0200, Thomas Monjalon wrote:
> 15/05/2019 08:52, Nithin Dabilpuram:
> > Hi Thomas,
> > On Tue, May 14, 2019 at 05:39:30PM +0200, Thomas Monjalon wrote:
> > > Hi,
> > > 
> > > 13/05/2019 13:21, Nithin Dabilpuram:
> > > > With the latest published interface of
> > > > rte_eal_hotplug_[add,remove](), and rte_eth_dev_close(),
> > > > rte_eth_dev_close() would cleanup all the data structures of
> > > > port's eth dev leaving the device common resource intact
> > > > if RTE_ETH_DEV_CLOSE_REMOVE is set in dev flags.
> > > > So "port detach" (~hotplug remove) should be able to work,
> > > > with device identifier like "port attach" as eth_dev could have
> > > > been closed already and rte_eth_devices[port_id] reused.
> > > 
> > > "port attach" uses devargs as identifier because there
> > > is no port id before creating it. But "detach port" uses
> > > logically the port id to close.
> > 
> > But if "port close" was already called on that port,
> > eth_dev->state would be set as RTE_ETH_DEV_UNUSED and
> > that port id could be reused.
> > So after "port close" if we call "port detach", isn't it
> > incorrect to use the same port id ?
> 
> Yes it is incorrect to close a port which is already closed :)
> 
> > > > This change alters "port detach" cmdline interface to
> > > > work with device identifier like "port attach".
> > > 
> > > The word "port" means an ethdev port, so it should be
> > > referenced with a port id.
> > > If you want to close an EAL rte_device, then you should
> > > rename the command.
> > > But testpmd purpose should be to work with ethdev ports only.
> > 
> > Renaming the command to "detach <identifier>" ?
> 
> Yes something like that.
> But why do you want to manage rte_device in testpmd?
> Being able to close ports in not enough?
> Please describe a scenario.
>

We just want to support testing hotplug detach along with
hotplug attach from testpmd. Currently there is no way to detach
if we close the port first.

Another reason is that in our new PMD, for detaching one specific port,
we need more than one try as the PMD might return -EAGAIN.
So with the current "port detach" implementation, after closing the port,
if PMD returns -EAGAIN for rte_dev_remove() call, there is no way to
try it again.
>