From: Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: linux-can <linux-can@vger.kernel.org>
Subject: Re: [PATCH 1/2] can: netlink: clear data_bittiming if fd is turned off
Date: Fri, 18 Jun 2021 18:58:28 +0900 [thread overview]
Message-ID: <CAMZ6RqJY5+UOGY8gBEQ76H8h09jeRaBkXRx6G4AhesLEM3Uoag@mail.gmail.com> (raw)
In-Reply-To: <20210618091015.kioemxe3j3cbx6qg@pengutronix.de>
On Fri. 18 juin 2021 at 18:10, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
>
> On 18.06.2021 17:19:03, Vincent Mailhol wrote:
> > When the FD is turned off through the netlink interface, the value
>
> values
>
> > still remain in data_bittiming and are displayed despite of the
> > feature being disabled.
> >
> > Example:
> >
> > $ ip link set can0 type can bitrate 500000 dbitrate 2000000 fd on
> > $ ip --details link show can0
> > 1: can0: <NOARP,ECHO> mtu 72 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 10
> > link/can promiscuity 0 minmtu 0 maxmtu 0
> > can <FD> state STOPPED restart-ms 0
> > bitrate 500000 sample-point 0.875
> > tq 12 prop-seg 69 phase-seg1 70 phase-seg2 20 sjw 1
> > ES582.1/ES584.1: tseg1 2..256 tseg2 2..128 sjw 1..128 brp 1..512 brp-inc 1
> > dbitrate 2000000 dsample-point 0.750
> > dtq 12 dprop-seg 14 dphase-seg1 15 dphase-seg2 10 dsjw 1
> > ES582.1/ES584.1: dtseg1 2..32 dtseg2 1..16 dsjw 1..8 dbrp 1..32 dbrp-inc 1
> > clock 80000000 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
> >
> > $ ip link set can0 type can bitrate 500000 fd off
> > $ ip --details link show can0
> > 1: can0: <NOARP,ECHO> mtu 16 qdisc pfifo_fast state DOWN mode DEFAULT group default qlen 10
> > link/can promiscuity 0 minmtu 0 maxmtu 0
> > can state STOPPED restart-ms 0
> > bitrate 500000 sample-point 0.875
> > tq 12 prop-seg 69 phase-seg1 70 phase-seg2 20 sjw 1
> > ES582.1/ES584.1: tseg1 2..256 tseg2 2..128 sjw 1..128 brp 1..512 brp-inc 1
> > dbitrate 2000000 dsample-point 0.750
> > dtq 12 dprop-seg 14 dphase-seg1 15 dphase-seg2 10 dsjw 1
> > ES582.1/ES584.1: dtseg1 2..32 dtseg2 1..16 dsjw 1..8 dbrp 1..32 dbrp-inc 1
> > clock 80000000 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
> >
> > Remark: once FD is turned off, it is not possible to just turn fd back
> > on and reuse the previously input data bittiming values:
>
> > $ ip link set can0 type can bitrate 500000 fd on
> > RTNETLINK answers: Operation not supported
> >
> > This means that the user will need to overwrite data bittiming with
> ^^^^^^^^^
> set
>
> At least with your change it's more a "set again" than to overwrite.
>
> > fresh values in order to turn fd on again.
> >
> > Because old data bittiming values can not be reused, this patch just
> > clears priv->data_bittiming whenever FD is turned off. This way, the
> > data bittiming variables are not displayed anymore.
> >
> > Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
> > ---
> > Hi Marc,
> >
> > I suggest to rebase this patch before the netlink TDC series.
>
> makes sense - If you're OK with the changes, I'll add them while
> applying.
I am OK with the changes.
> Your patch makes the interface consistent, another option would be to
> allow FD mode if the data bit timing values have been set before.
> Opinions?
One part of me says it would make sense but let's also try to be
realistic. The only reason I spotted this issue is because I was
actively trying to find defects while testing my TDC
implementation. Under normal usage, I never had have such needs.
How many people will need to set fd on, then off, then on again?
Too few I think. Let's force those few people to always provide
the data bittiming values. The overhead which would be needed to
implement this in drivers/net/can/dev/netlink.c is just not worth it.
> 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 |
next prev parent reply other threads:[~2021-06-18 9:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-18 8:19 [PATCH 0/2] Stop showing data bittiming if FD is turned off Vincent Mailhol
2021-06-18 8:19 ` [PATCH 1/2] can: netlink: clear data_bittiming if fd " Vincent Mailhol
2021-06-18 9:10 ` Marc Kleine-Budde
2021-06-18 9:58 ` Vincent MAILHOL [this message]
2021-06-18 8:19 ` [PATCH 2/2] can: netlink: clear tdc " Vincent Mailhol
2021-06-18 9:11 ` Marc Kleine-Budde
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