linux-kernel - Re: [PATCH 0/3] Add NETIF_F_HW

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Date:   Fri, 23 Aug 2019 01:09:50 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>,
        roopa@...ulusnetworks.com, davem@...emloft.net,
        UNGLinuxDriver@...rochip.com, alexandre.belloni@...tlin.com,
        allan.nielsen@...rochip.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH 0/3] Add NETIF_F_HW_BRIDGE feature

On 22/08/2019 22:07, Horatiu Vultur wrote:
> Current implementation of the SW bridge is setting the interfaces in
> promisc mode when they are added to bridge if learning of the frames is
> enabled.
> In case of Ocelot which has HW capabilities to switch frames, it is not
> needed to set the ports in promisc mode because the HW already capable of
> doing that. Therefore add NETIF_F_HW_BRIDGE feature to indicate that the
> HW has bridge capabilities. Therefore the SW bridge doesn't need to set
> the ports in promisc mode to do the switching.
> This optimization takes places only if all the interfaces that are part
> of the bridge have this flag and have the same network driver.
> 
> If the bridge interfaces is added in promisc mode then also the ports part
> of the bridge are set in promisc mode.
> 
> Horatiu Vultur (3):
>   net: Add HW_BRIDGE offload feature
>   net: mscc: Use NETIF_F_HW_BRIDGE
>   net: mscc: Implement promisc mode.
> 
>  drivers/net/ethernet/mscc/ocelot.c | 26 ++++++++++++++++++++++++--
>  include/linux/netdev_features.h    |  3 +++
>  net/bridge/br_if.c                 | 29 ++++++++++++++++++++++++++++-
>  net/core/ethtool.c                 |  1 +
>  4 files changed, 56 insertions(+), 3 deletions(-)
> 

IMO the name is misleading.
Why do the devices have to be from the same driver ? This is too specific targeting some
devices. The bridge should not care what's the port device, it should be the other way
around, so adding device-specific code to the bridge is not ok. Isn't there a solution
where you can use NETDEV_JOIN and handle it all from your driver ?
Would all HW-learned entries be hidden from user-space in this case ?