linux-kernel - Re: [PATCH] can: mcba_usb: Fix termination command argument

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Date:   Thu, 24 Nov 2022 09:53:33 +0900
From:   Vincent Mailhol <vincent.mailhol@...il.com>
To:     Yasushi SHOJI <yasushi.shoji@...il.com>
Cc:     Yasushi SHOJI <yashi@...cecubics.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] can: mcba_usb: Fix termination command argument

On Thu. 24 Nov. 2022 at 04:53, Yasushi SHOJI <yasushi.shoji@...il.com> wrote:
> Microchip USB Analyzer can be set with termination setting ON or OFF.
> As I've observed, both with my oscilloscope and USB packet capture
> below, you must send "0" to turn it ON, and "1" to turn it OFF.
>
> Reverse the argument value to fix this.
>
> These are the two commands sequence, ON then OFF.
>
> > No.     Time           Source                Destination           Protocol Length Info
> >       1 0.000000       host                  1.3.1                 USB      46     URB_BULK out
> >
> > Frame 1: 46 bytes on wire (368 bits), 46 bytes captured (368 bits)
> > USB URB
> > Leftover Capture Data: a80000000000000000000000000000000000a8
> >
> > No.     Time           Source                Destination           Protocol Length Info
> >       2 4.372547       host                  1.3.1                 USB      46     URB_BULK out
> >
> > Frame 2: 46 bytes on wire (368 bits), 46 bytes captured (368 bits)
> > USB URB
> > Leftover Capture Data: a80100000000000000000000000000000000a9
>
> Signed-off-by: Yasushi SHOJI <yashi@...cecubics.com>
> ---
>  drivers/net/can/usb/mcba_usb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
> index 218b098b261d..67beff1a3876 100644
> --- a/drivers/net/can/usb/mcba_usb.c
> +++ b/drivers/net/can/usb/mcba_usb.c
> @@ -785,9 +785,9 @@ static int mcba_set_termination(struct net_device *netdev, u16 term)
>         };
>
>         if (term == MCBA_TERMINATION_ENABLED)
> -               usb_msg.termination = 1;
> -       else
>                 usb_msg.termination = 0;
> +       else
> +               usb_msg.termination = 1;
>
>         mcba_usb_xmit_cmd(priv, (struct mcba_usb_msg *)&usb_msg);

Nitpick: does it make sense to rename the field to something like
usb_msg.termination_disable or usb_msg.termination_off? This would
make it more explicit that this is a "reverse" boolean.