netdev - Re: [PATCH net-next v4 00/24] switchdev: spring cleanup

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Message-ID: <552CAA0C.3030009@cumulusnetworks.com>
Date:	Mon, 13 Apr 2015 22:47:56 -0700
From:	roopa <roopa@...ulusnetworks.com>
To:	sfeldma@...il.com
CC:	netdev@...r.kernel.org, jiri@...nulli.us, linux@...ck-us.net,
	f.fainelli@...il.com, sridhar.samudrala@...el.com,
	ronen.arad@...el.com, andrew@...n.ch
Subject: Re: [PATCH net-next v4 00/24] switchdev: spring cleanup

On 4/12/15, 11:16 PM, sfeldma@...il.com wrote:
> From: Scott Feldman <sfeldma@...il.com>
>
> v4:
>
> Well, it was a lot of work, but now prepare-commit transaction model is how
> davem advises: if prepare fails, abort the transaction.  The driver must do
> resource reservations up front in prepare phase and return those resources if
> aborting.  Commit phase would use reserved resources.  The good news is the
> driver code (for rocker) now handles resource allocation failures better by not
> leaving partially device or driver states.  This is a side-effect of the
> prepare phase where state isn't modified; only validation of inputs and
> resource reservations happen in the prepare phase.  Since we're supporting
> setting attrs and add objs across lower devs in the stacked case, we need to
> hold rtnl_lock (or ensure rtnl_lock is held) so lower devs don't move on us
> during the prepare-commit transaction.  DSA driver code skips the prepare phase
> and goes straight for the commit phase since no up-front allocations are done
> and no device failures (that could be detected in the prepare phase) can
> happen.

thanks for the series. It definitely does look cleaner and less 
confusing now!.
I do love the abstraction but i was one of the people voting against 
duplicating the
kernel objects into swdev objs which this patches does (which i am still 
not convinced
we should have).

>
> Remove NETIF_F_HW_SWITCH_OFFLOAD from rocker and the swdev_attr_set/get
> wrappers.  DSA doesn't set NETIF_F_HW_SWITCH_OFFLOAD, so it can't be in
> swdev_attr_set/get.  rocker doesn't need it; or rather can't support
> NETIF_F_HW_SWITCH_OFFLOAD being set/cleared at run-time after the device
> port is already up and offloading L2/L3.  NETIF_F_HW_SWITCH_OFFLOAD is still
> left as a feature flag for drivers that can use it.

I see that this series removes all uses of it in the switchdev api 
later. I had summarized
the need for the flag in reply to one of your questions a few weeks 
back. Since you have moved all
ndo ops to swdev ops (including ndo_bridge_setlink/dellink), I don't 
want to hold on to the
  feature flag if no one is using it. yes, my userspace driver uses it 
today.
I will come back with stronger justification to keep it or
will submit a patch to remove it and add it back at a later point if needed.


Thanks,
Roopa

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