On 1/17/2018 4:05 PM, Stephen Hemminger wrote:
> On Wed, 17 Jan 2018 14:32:17 +0000
> Ferruh Yigit <ferruh.yi...@intel.com> wrote:
>
>> On 1/17/2018 7:56 AM, Andrew Rybchenko wrote:
>>> On 01/16/2018 09:37 PM, Stephen Hemminger wrote:
>>>> While reviewing drivers, noticed a lot of unnecessary
>>>> duplication of code in drivers for handling the eth_dev link status
>>>> information. While consolidating this, it also became obvious that
>>>> some drivers behave differently for no good reason.
>>>>
>>>> It also was a good chance to introduce atomic exchange primitives
>>>> in EAL because there are other places using cmpset where not
>>>> necessary (such as bonding).
>>>>
>>>> Mostly only compile tested only, don't have all of the hardware
>>>> available (except ixgbe and virtio) to test.
>>>>
>>>> Note: the eth_dev_link_update function return value is inconsistent
>>>> across drivers. Should be changed to be void.
>>>
>>> I would say "link_update" callback return value is inconsistent across
>>> drivers. I'm not sure which direction is right here: make it consistent
>>> or make it void. Also any changes in link information could be
>>> important. As I understand it should not happen without up/down,
>>> but bugs with loss of intermediate transitions are definitely possible.
>>> So, notifying about any changes in link information is definitely safer.
>>> May be not now.
>>
>> Again, why not return previous link status, it is simple enough to prevent
>> inconsistent usage.
>>
>> rte_eth_link_get() already discards the return value, so won't be a problem
>> there.
>>
>> For the cases PMD would like know about link changes, they will need to
>> implement almost same link_update function with a return value, so why not
>> use
>> existing link_update function?
>>
>> Like been in virtio, link_update() used in interrupt handler, and calls a
>> callback process if status changes. When link_update() return status changed
>> to
>> void, I guess they will need to implement another version of the link_update
>> with return and use it.
>
> The interrupt and non-interrupt model are different.
Yes. But for virtio specific usage:
virtio_interrupt_handler()
virtio_dev_link_update() == 0
_rte_eth_dev_callback_process()
meantime same exact virtio_dev_link_update() used as:
.link_update = virtio_dev_link_update,
so updating virtio_dev_link_update() to not return status change, will update
logic in virtio_interrupt_handler(), no?
> Also the driver internally may want to do something different, this is about
> the return value for dev_ops->link_update.
Agreed, driver may do something different. And the function needs to be
implemented will be very close to dev_ops->link_update. I thought making
dev_ops->link_update more generic can prevent duplication there. And aligns with
virtio usage..
> The code in rte_eth_dev never
> used the return value. The bonding driver was expecting it to work but it
> doesn't.
Agreed.
> Anyway drivers shouldn't in general be directly calling other
> devices eth_dev_ops
I guess now there are a few overlay PMDs does this.
