[dpdk-dev] [PATCH v8 5/5] doc: add description of the NIC reset API

[Remy Horton]

Unless the plan is for this patch to be squashed, ought to have a brief 
commit message..

On 17/07/2017 16:15, Wei Dai wrote:
> Signed-off-by: Wei Dai <wei.dai at intel.com>
> ---
>  doc/guides/prog_guide/poll_mode_drv.rst | 40 +++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)

Reviewed-by: Remy Horton <remy.horton at intel.com>


> +.. code-block:: c
> +
> +    int rte_eth_dev_reset(uint8_t port_id);
> +

Suggest following text:

Sometimes a port has to be reset passively. For example when a PF is 
reset, all its VFs should also be reset by the application to make them 
consistent with the PF. A DPDK application also can call this function 
to trigger a port reset. Normally, a DPDK application would invokes this 
function when an RTE_ETH_EVENT_INTR_RESET event is detected.

It is the duty of the PMD to trigger RTE_ETH_EVENT_INTR_RESET events and 
the application should register a callback function to handle these 
events. When a PMD needs to trigger a reset, it can trigger an 
RTE_ETH_EVENT_INTR_RESET event. On receiving an RTE_ETH_EVENT_INTR_RESET 
event, applications can handle it as follows: Stop working queues, stop 
calling Rx and Tx functions, and then call rte_eth_dev_reset( ). For 
thread safety all these operations should be called from the same thread.

For example when PF is reset, the PF sends a message to notify VFs of 
this event and also trigger an interrupt to VFs. Then in the interrupt 
service routine the VFs detects this notification message and calls 
_rte_eth_dev_callback_process(dev, RTE_ETH_EVENT_INTR_RESET, NULL, 
NULL). This means that a PF reset triggers an RTE_ETH_EVENT_INTR_RESET 
event within VFs. The function _rte_eth_dev_callback_process( ) will 
call the registered callback function. The callback function can trigger 
the application to handle all operations the VF reset requires including 
stopping Rx/Tx queues and calling rte_eth_dev_reset().

The rte_eth_dev_reset( ) itself is a generic function which only does 
some hardware reset operations through calling dev_unint() and 
dev_init(), and itself does not handle synchronization, which is handled 
by application.

The PMD itself should not call rte_eth_dev_reset( ). The PMD can trigger 
the application to handle reset event. It is duty of application to 
handle all synchronization before it calls rte_eth_dev_reset( ).


..Remy