linux-kernel - Re: [RFC PATCH v3 8/9] can: slcan: add support to set bit time register (btr)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CABGWkvqF4HSKVrO8W8oyDPCMfx_B2xQZ_EWET11RZb6k8Kmb=w@mail.gmail.com>
Date:   Wed, 27 Jul 2022 19:28:45 +0200
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-can@...r.kernel.org,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        michael@...rulasolutions.com,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        Jeroen Hofstee <jhofstee@...tronenergy.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        netdev@...r.kernel.org,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Max Staudt <max@...as.org>
Subject: Re: [RFC PATCH v3 8/9] can: slcan: add support to set bit time
 register (btr)

On Wed, Jul 27, 2022 at 7:21 PM Marc Kleine-Budde <mkl@...gutronix.de> wrote:
>
> On 27.07.2022 17:55:10, Dario Binacchi wrote:
> > Hello Marc,
> >
> > On Wed, Jul 27, 2022 at 1:31 PM Marc Kleine-Budde <mkl@...gutronix.de> wrote:
> > >
> > > On 26.07.2022 23:02:16, Dario Binacchi wrote:
> > > > It allows to set the bit time register with tunable values.
> > > > The setting can only be changed if the interface is down:
> > > >
> > > > ip link set dev can0 down
> > > > ethtool --set-tunable can0 can-btr 0x31c
> > > > ip link set dev can0 up
> > >
> > > As far as I understand, setting the btr is an alternative way to set the
> > > bitrate, right?
> >
> > I thought of a non-standard bitrate or, in addition to the bitrate, the
> > possibility of enabling some specific CAN controller options. Maybe Oliver
> > could help us come up with the right answer.
> >
> > This is the the slcan source code:
> > https://github.com/linux-can/can-utils/blob/cad1cecf1ca19277b5f5db39f8ef6f8ae426191d/slcand.c#L331
> > btr case cames after speed but they don't seem to be considered alternative.
> >
> > > I don't like the idea of poking arbitrary values into a
> > > hardware from user space.
> >
> > However this is already possible through the slcand and slcan_attach
> > applications.
> > Furthermore, the driver implements the LAWICEL ASCII protocol for CAN
> > frame transport over serial lines,
> > and this is one of the supported commands.
> >
> > >
> > > Do you have a use case for this?
> >
> > I use the applications slcand and slcan_attach as a reference, I try to make the
> > driver independent from them for what concerns the CAN setup. And the bit time
> > register setting is the last dependency.
>
> Ok - We avoided writing bit timing registers from user space into the
> hardware for all existing drivers. If there isn't a specific use case,
> let's skip this patch. If someone comes up with a use case we can think
> of a proper solution.

Ok. So do I also remove the 7/9 "ethtool: add support to get/set CAN
bit time register"
patch ?

Thanks and regards,
Dario

>
> 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 |



-- 

Dario Binacchi

Embedded Linux Developer

dario.binacchi@...rulasolutions.com

__________________________________


Amarula Solutions SRL

Via Le Canevare 30, 31100 Treviso, Veneto, IT

T. +39 042 243 5310
info@...rulasolutions.com

www.amarulasolutions.com