netdev - Re: [PATCH net-next] mlx5: count all link events

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Date:   Wed, 19 May 2021 22:36:10 -0700
From:   Saeed Mahameed <saeed@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Lijun Pan <ljp@...ux.vnet.ibm.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] mlx5: count all link events

On Wed, 2021-05-19 at 13:56 -0700, Jakub Kicinski wrote:
> On Wed, 19 May 2021 13:18:36 -0700 Saeed Mahameed wrote:
> > On Wed, 2021-05-19 at 12:51 -0700, Jakub Kicinski wrote:
> > > 
> > > 
> > > I assumed netif_carrier_event() would be used specifically in
> > > places
> > > driver is actually servicing a link event from the device, and
> > > therefore is relatively certain that _something_ has happened.  
> > 
> > then according to the above assumption it is safe to make
> > netif_carrier_event() do everything.
> > 
> > netif_carrier_event(netdev, up) {
> >         if (dev->reg_state == NETREG_UNINITIALIZED)
> >                 return;
> > 
> >         if (up == netif_carrier_ok(netdev) {
> >                 atomic_inc(&netdev->carrier_up_count);
> >                 atomic_inc(&netdev->carrier_down_count);
> >                 linkwatch_fire_event(netdev);
> >         }
> > 
> >         if (up) {
> >                 netdev_info(netdev, "Link up\n");
> >                 netif_carrier_on(netdev);
> >         } else {
> >                 netdev_info(netdev, "Link down\n");
> >                 netif_carrier_off(netdev);
> >         }
> > }
> 
> Two things to consider are:
>  - some drivers print more info than just "link up/link down" so
> they'd
>    have to drop that extra stuff (as much as I'd like the
> consistency)

+1 for the consistency

>  - again with the unnecessary events I was afraid that drivers reuse 
>    the same handler for device events and to read the state in which
>    case we may do something like:
> 
>         if (from_event && up == netif_carrier_ok(netdev)
> 

I don't actually understand your point here .. what kind of scenarios
it is wrong to use this function ? 

But anyway, the name of the function makes it very clear this is from
event.. 
also we can document this.

> Maybe we can revisit when there's more users?
goes both ways :), we can do what fits the requirement for mlx5 now and
revisit in the future, if we do believe this should be general behavior
for all/most vendors of-course!