Re: [dpdk-dev] [PATCH v10 20/20] ethdev: add control interface support

[Yuanhan Liu <yliu@fridaylinux.org>]

On Tue, Jul 04, 2017 at 05:13:37PM +0100, Ferruh Yigit wrote:
> @@ -157,8 +164,12 @@ rte_eth_dev_pci_generic_probe(struct rte_pci_device *pci_dev,
>  
>  	RTE_FUNC_PTR_OR_ERR_RET(*dev_init, -EINVAL);
>  	ret = dev_init(eth_dev);
> -	if (ret)
> +	if (ret) {
>  		rte_eth_dev_pci_release(eth_dev);
> +		return ret;
> +	}
> +
> +	rte_eth_control_interface_create(eth_dev->data->port_id);

Hi,

So you are creating a virtual kernel interface for each PCI port. What
about the VDEVs? If you plan to create one for each port, why not create
it at the stage while allocating the eth device, or at the stage while
starting the port if the former is too earlier?

Another thing comes to my mind is have you tried it with multi-process
model? Looks like it will create the control interface twice? Or it will
just be failed since the interface already exists?


I also have few questions regarding the whole design. So seems that the
ctrl_if only exports two APIs and they all will be only used in the EAL
layer. Thus, one question is did you plan to let APP use them? Judging
EAL already calls them automatically, I don't think it makes sense to
let the APP call it again. That being said, what's the point of the making
it be an lib? Why not just put it under EAL or somewhere else, and let
EAL invoke it as normal helper functions (instead of by public APIs)?

I will avoid adding a new lib if possible. Otherwise, it increases the
chance of ABI/API breakage is needed in future for extensions.

The same question goes to the ethtool lib. Since your solution can work
well with the well-known ethtool, which is also way more widely available
than the DPDK ethtool app, what's the point of keeping the ethtool app
then? Like above, I also don't think those APIs are meant for APPs (or
are they?). Thus, with the ethtool app removed, we then could again avoid
introducing a new lib.

	--yliu