Re: [dpdk-dev] [PATCH v2 2/3] net/mlx5: fix link status behavior

[Yongseok Koh <yskoh@mellanox.com>]

On Mon, Mar 12, 2018 at 02:43:18PM +0100, Nelio Laranjeiro wrote:
> This behavior is mixed between what should be handled by the application
> and what is under PMD responsibility.
> 
> According to DPDK API:
> - link_update() should only query the link status [1]
> - link_set_{up,down}() should only set the link to the according status [1]
> - dev_{start,stop}() should enable/disable traffic reception/emission [2]

The description of rte_eth_dev_set_link_up() is [1] :
	The device rx/tx functionality will be disabled if success, and it can
	be re-enabled with a call to rte_eth_dev_set_link_up()

This means, if user runs "set link-down port 0" on testpmd, traffic should stop
by disabling Rx/Tx on device. But unfortunately, mlx5 doesn't have a way to stop
device but it rather relies on kernel implementation - e.g. SIOCSIFFLAGS. So,
even if the command is run, traffic goes on. I guess the original
implementation might be needed to workaround this situation.

Shall we talk to HW and driver people regarding how to access dev (or PHY) from
user-level?

[1] http://dpdk.org/doc/api/rte__ethdev_8h.html#a51d7a0d2bb4202f9ebf9f174ba1f6e5c

Thanks,
Yongseok