linux-kernel - Re: [PATCH v3 3/4] can: skb:: move can_dropped_invalid_skb and can_skb_headroom

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Date:   Wed, 18 May 2022 15:28:11 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Oliver Hartkopp <socketcan@...tkopp.net>
Cc:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>,
        Max Staudt <max@...as.org>, linux-can@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 3/4] can: skb:: move can_dropped_invalid_skb and
 can_skb_headroom_valid to skb.c

On 18.05.2022 15:10:44, Oliver Hartkopp wrote:
> On 18.05.22 14:03, Vincent MAILHOL wrote:
> > I didn't think this would trigger such a passionate discussion!
> 
> :-D
>
> Maybe your change was the drop that let the bucket run over ;-)

It's so trivial that everybody feels the urge to say something. :D

> > > But e.g. the people that are running Linux instances in a cloud only
> > > using vcan and vxcan would not need to carry the entire infrastructure
> > > of CAN hardware support and rx-offload.
> > 
> > Are there really some people running custom builds of the Linux kernel
> > in a cloud environment? The benefit of saving a few kilobytes by not
> > having to carry the entire CAN hardware infrastructure is blown away
> > by the cost of having to maintain a custom build.
> 
> When looking to the current Kconfig and Makefile content in
> drivers/net/can(/dev) there is also some CONFIG_CAN_LEDS which "depends on
> BROKEN" and builds a leds.o from a non existing leds.c ?!?
> 
> Oh leds.c is in drivers/net/can/leds.c but not in drivers/net/can/dev/leds.c
> where it could build ... ?
> 
> So what I would suggest is that we always build a can-dev.ko when a CAN
> driver is needed.
> 
> Then we have different options that may be built-in:
> 
> 1. netlink hw config interface
> 2. bitrate calculation
> 3. rx-offload
> 4. leds
> 
> E.g. having the netlink interface without bitrate calculation does not make
> sense to me too.

ACK

> > I perfectly follow the idea to split rx-offload. Integrators building
> > some custom firmware for an embedded device might want to strip out
> > any unneeded piece. But I am not convinced by this same argument when
> > applied to v(x)can.
> 
> It does. I've seen CAN setups (really more than one or two!) in VMs and
> container environments that are fed by Ethernet tunnels - sometimes also in
> embedded devices.
> 
> > A two level split (with or without rx-offload) is what makes the most
> > sense to me.
> > 
> > Regardless, having the three level split is not harmful. And because
> > there seems to be a consensus on that, I am fine to continue in this
> > direction.
> 
> Thanks!
> 
> Should we remove the extra option for the bitrate calculation then?

+1

> And what about the LEDS support depending on BROKEN?
> That was introduced by commit 30f3b42147ba6f ("can: mark led trigger as
> broken") from Uwe as it seems there were some changes in 2018.

There's a proper generic LED trigger now for network devices. So remove
LED triggers, too.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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