[dpdk-dev] [PATCH v7 13/15] eal: add hotplug add/remove functions

[Gaëtan Rivet]

On Fri, Jun 30, 2017 at 06:03:17PM +0200, Thomas Monjalon wrote:
> 30/06/2017 17:44, Jan Blunck:
> > On Fri, Jun 30, 2017 at 11:20 AM, Bruce Richardson
> > <bruce.richardson at intel.com> wrote:
> > > On Fri, Jun 30, 2017 at 11:11:42AM +0200, Gaėtan Rivet wrote:
> > >> On Fri, Jun 30, 2017 at 11:06:03AM +0200, Thomas Monjalon wrote:
> > >> > 29/06/2017 20:22, Jan Blunck:
> > >> > >  /**
> > >> > > + * Hotplug add a given device to a specific bus.
> > >> > > + *
> > >> > > + * @param busname
> > >> > > + *   The bus name the device is added to.
> > >> > > + * @param devname
> > >> > > + *   The device name. Based on this device name, eal will identify a driver
> > >> > > + *   capable of handling it and pass it to the driver probing function.
> > >> > > + * @param devargs
> > >> > > + *   Device arguments to be passed to the driver.
> > >> > > + * @return
> > >> > > + *   0 on success, negative on error.
> > >> > > + */
> > >> > > +int rte_eal_hotplug_add(const char *busname, const char *devname,
> > >> > > +                 const char *devargs);
> > >> >
> > >> > After the hotplug, we may need to get the rte_device.
> > >> > Should we add a struct **rte_device as parameter,
> > >> > or should we add a helper function to get the rte_device
> > >> > from busname and devname?
> > >>
> > >> Also possible: return a struct *rte_device and set rte_errno on error.
> > >>
> > > +1 for this option.
> > 
> > Given that the caller of this is usually something that injects events
> > from the system I wonder what it is going to do with a rte_device
> > reference. Additionally to what the caller knows anyway (name,
> > numa_node, devargs) it can check if a driver got assigned. Sure the
> > caller could upcast conditionally based on the busname ...
> > 
> > At this point I guess the control plane would anyway want to get
> > access to a high-level object, e.g. the rte_ethdev. I believe it is
> > better to decouple this through callbacks that can get registered with
> > individual buses.
> 
> I think Gaetan has an example of use of rte_device after plugging
> with the failsafe PMD (managing slaves).
> Anyway, it can be discussed later with a real example of use if needed.
> We have a couple of weeks before freezing the API.

The rte_device should be accessible from the rte_eth_dev anyway so it
does not make much difference. As long as a handle on the device is
available. It is of course possible to add yet another callback to
search the device just plugged, but I don't see a reason here not to do
it in one pass.

-- 
Gaëtan Rivet
6WIND