linux-kernel - Re: [PATCH 2/3] can: esd_usb: Improved behavior on esd CAN_ERROR

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Message-ID: <a1d253bacdf296947a45fb069a0fd64eabb7e117.camel@esd.eu>
Date:   Wed, 21 Dec 2022 18:29:23 +0000
From:   Frank Jungclaus <Frank.Jungclaus@....eu>
To:     "mailhol.vincent@...adoo.fr" <mailhol.vincent@...adoo.fr>
CC:     Stefan Mätje <Stefan.Maetje@....eu>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        "mkl@...gutronix.de" <mkl@...gutronix.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "wg@...ndegger.com" <wg@...ndegger.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] can: esd_usb: Improved behavior on esd CAN_ERROR_EXT
 event (2)

On Tue, 2022-12-20 at 14:49 +0900, Vincent MAILHOL wrote:
> On Tue. 20 Dec. 2022 at 06:29, Frank Jungclaus <frank.jungclaus@....eu> wrote:
> > Started a rework initiated by Vincents remarks "You should not report
> > the greatest of txerr and rxerr but the one which actually increased."
> > [1]
> 
> I do not see this comment being addressed. You are still assigning the
> flags depending on the highest value, not the one which actually
> changed.


Yes, I'm assigning depending on the highest value, but from my point of
view doing so is analogue to what is done by can_change_state(). And
it should be fine, because e.g. my "case ESD_BUSSTATE_WARN:" is reached
exactly once while the transition from ERROR_ACTIVE to
ERROR_WARN. Than one of rec or tec is responsible for this
transition.
There is no second pass for "case ESD_BUSSTATE_WARN:"
when e.g. rec is already on WARN (or above) and now tec also reaches
WARN.
Man, this is even difficult to explain in German language ;)


> 
> > and "As far as I understand, those flags should be set only when
> > the threshold is *reached*" [2] .
> > 
> > Now setting the flags for CAN_ERR_CRTL_[RT]X_WARNING and
> > CAN_ERR_CRTL_[RT]X_PASSIVE regarding REC and TEC, when the
> > appropriate threshold is reached.
> > 
> > Fixes: 96d8e90382dc ("can: Add driver for esd CAN-USB/2 device")
> > Signed-off-by: Frank Jungclaus <frank.jungclaus@....eu>
> > Link: [1] https://lore.kernel.org/all/CAMZ6RqKGBWe15aMkf8-QLf-cOQg99GQBebSm+1wEzTqHgvmNuw@mail.gmail.com/
> > Link: [2] https://lore.kernel.org/all/CAMZ6Rq+QBO1yTX_o6GV0yhdBj-RzZSRGWDZBS0fs7zbSTy4hmA@mail.gmail.com/
> > ---
> >  drivers/net/can/usb/esd_usb.c | 14 ++++++++------
> >  1 file changed, 8 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/net/can/usb/esd_usb.c b/drivers/net/can/usb/esd_usb.c
> > index 5e182fadd875..09745751f168 100644
> > --- a/drivers/net/can/usb/esd_usb.c
> > +++ b/drivers/net/can/usb/esd_usb.c
> > @@ -255,10 +255,18 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
> >                                 can_bus_off(priv->netdev);
> >                                 break;
> >                         case ESD_BUSSTATE_WARN:
> > +                               cf->can_id |= CAN_ERR_CRTL;
> > +                               cf->data[1] = (txerr > rxerr) ?
> > +                                               CAN_ERR_CRTL_TX_WARNING :
> > +                                               CAN_ERR_CRTL_RX_WARNING;
> 
> Nitpick: when a ternary operator is too long to fit on one line,
> prefer an if/else.

AFAIR line length up to 120 chars is tolerated nowadays. So putting
this on a single line might also be an option!(?)
How will this be handled in the CAN sub tree?


> 
> >                                 priv->can.state = CAN_STATE_ERROR_WARNING;
> >                                 priv->can.can_stats.error_warning++;
> >                                 break;
> >                         case ESD_BUSSTATE_ERRPASSIVE:
> > +                               cf->can_id |= CAN_ERR_CRTL;
> > +                               cf->data[1] = (txerr > rxerr) ?
> > +                                               CAN_ERR_CRTL_TX_PASSIVE :
> > +                                               CAN_ERR_CRTL_RX_PASSIVE;
> 
> Same.
> 
> >                                 priv->can.state = CAN_STATE_ERROR_PASSIVE;
> >                                 priv->can.can_stats.error_passive++;
> >                                 break;
> > @@ -296,12 +304,6 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
> >                         /* Bit stream position in CAN frame as the error was detected */
> >                         cf->data[3] = ecc & SJA1000_ECC_SEG;
> > 
> > -                       if (priv->can.state == CAN_STATE_ERROR_WARNING ||
> > -                           priv->can.state == CAN_STATE_ERROR_PASSIVE) {
> > -                               cf->data[1] = (txerr > rxerr) ?
> > -                                       CAN_ERR_CRTL_TX_PASSIVE :
> > -                                       CAN_ERR_CRTL_RX_PASSIVE;
> > -                       }
> >                         cf->data[6] = txerr;
> >                         cf->data[7] = rxerr;
> >                 }
> 
> Yours sincerely,
> Vincent Mailhol