Re: [dpdk-dev] [PATCH v4 1/3] lib/librte_ether: add support for port reset

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2017-04-14 01:29, Zhao1, Wei:
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > 2017-04-13 08:55, Zhao1, Wei:
> > > From: Ananyev, Konstantin
> > > > From: Zhao1, Wei
> > > > > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > > > > > 2017-04-06 02:57, Zhao1, Wei:
> > > > > > > >   /**
> > > > > > > > > + * Reset an ethernet device when it's not working. One
> > > > > > > > > + scenario is, after PF
> > > > > > > > > + * port is down and up, the related VF port should be reset.
> > > > > > > > > + * The API will stop the port, clear the rx/tx queues,
> > > > > > > > > + re-setup the rx/tx
> > > > > > > > > + * queues, restart the port.
> > > > > > > >
> > > > > > > > s/The API/This function/
> > > > > > > >
> > > > > > > > Please explain exactly the responsibility of this function,
> > > > > > > > and how it is different from calling stop/configure/start.
> > > > > > >
> > > > > > > In this reset feature, reset function can do the calling
> > > > > > > stop/configure/start process, but also It can also do some
> > > > > > > restore work for the port, for example, it can restore the
> > > > > > > added parameters  of
> > > > > > vlan,  mac_addrs, promisc_unicast_enabled falg and
> > > > > > promisc_multicast_enabled flag.
> > > >
> > > > Ok, but why start/stop can't do these things?
> > > > Konstantin
> > >
> > > This is because in i40e PMD code, start and stop process do not have
> > > the process of store and restore the added key parameters. Not  only
> > > i40e but also other PMD code. So, in the function pointed to by dev_reset,
> > we add specific function do store and restore of some of the important
> > parameters  listed above.
> > 
> > Why store and restore cannot be implemented in start/stop functions?
> 
> Because reset and  start/stop are used for two purposes,  for example:
> Some user maybe just start/stop the port  and he do not care what key parameters
> has been configuration last time, and even worse when he want to clear all the configuration last time ,
> if we add specific function do store and restore in  that two function, it is useless for them,
> and may cause a result that user do not expect.

Is it said somewhere in the doc that the configuration is lost when
stopping a device?
Can we say which configuration parameter is kept and which one is lost?

rte_eth_dev_config_restore() is called in rte_eth_dev_start().