Re: [dpdk-dev] [RFC] ethdev: complete closing to free all resources

[Thomas Monjalon <thomas@monjalon.net>]

28/09/2018 14:46, Ferruh Yigit:
> On 9/8/2018 12:39 AM, Thomas Monjalon wrote:
> > After closing a port, it cannot be restarted.
> > So there is no reason to not free all associated resources.
> > 
> > The last step was done with rte_eth_dev_detach() which is deprecated.
> > Instead of removing the associated rte_device, the driver should check
> > if no more port (ethdev, cryptodev, etc) is still open for the device.
> > Then the device resources can be freed by the driver inside the
> > dev_close() driver callback operation.
> > 
> > The last ethdev freeing (dev_private and final release), which were done
> > by rte_eth_dev_detach(), are now done at the end of rte_eth_dev_close().
> > 
> > Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> > ---
> > This patch contains only the change in the close function as RFC.
> > 
> > This idea was presented at Dublin during the "hotplug talk".
> > ---
> > @@ -1372,6 +1373,10 @@ rte_eth_dev_close(uint16_t port_id)
> >  	dev->data->nb_tx_queues = 0;
> >  	rte_free(dev->data->tx_queues);
> >  	dev->data->tx_queues = NULL;
> > +
> > +	rte_free(dev->data->dev_private);
> > +
> > +	rte_eth_dev_release_port(dev);
> 
> These already done in:
> rte_eth_dev_pci_generic_remove()
> 	rte_eth_dev_pci_release()
> 
> Perhaps all content of rte_eth_dev_pci_release(), including above updates,
> should move to rte_eth_dev_close() and rte_eth_dev_pci_generic_remove() call
> rte_eth_dev_close() directly.

Yes I think it is the way to go:
	- when removing a rte_device, close all associated ports.
and the reverse can be done in addition:
	- when closing the last port of a rte_device, remove it.

> Just thinking aloud,
> 
> driver->probe() called when a new device added.
> Application startup can be thought as all devices added one by one. [Perhaps
> this can be change in the future to add devices only when explicitly stated]
> 
> driver->remove() called when device removed.
> When application terminated this path not called at all, perhaps we need a way
> to remove all devices one by one on exit.
> 
> eth_dev_close(), when eth_dev removed in ethdev layer but device is not removed
> in eal level,
> 
> I think it make sense for eth_dev_close():
> - It does more cleanup, free resources and port_id
> - but it may need to do more clean up, like call uninit() and do more driver
> internal clean up too, and clean up the hw.
> - so call stack can be:
>   driver->remove()
>     rte_eth_dev_pci_generic_remove()
>       eth_dev_close()
>         dev_uninit() [driver unint function ]
> 
> 
> Another question, after eth_dev_close() ethdev is not usable and not able to
> restart it back. So why we need eth_dev_close() in addition to dev remove, why
> not directly call rte_eth_dev_detach()?

rte_eth_dev_detach is assuming a 1:1 mapping between
EAL rte_device and rte_eth_dev port.
That's why it is deprecated and going to be removed.