linux-kernel - Re: [PATCH 3/3] can: esd_usb: Improved decoding for ESD_EV_CAN_ERROR

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Date:   Wed, 21 Dec 2022 18:01:50 +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 3/3] can: esd_usb: Improved decoding for
 ESD_EV_CAN_ERROR_EXT messages

On Tue, 2022-12-20 at 17:53 +0900, Vincent MAILHOL wrote:
> On Tue. 20 Dec. 2022 at 14:27, Vincent MAILHOL
> <mailhol.vincent@...adoo.fr> wrote:
> > Le mar. 20 déc. 2022 à 06:28, Frank Jungclaus <frank.jungclaus@....eu> a écrit :
> > > As suggested by Marc there now is a union plus a struct ev_can_err_ext
> > > for easier decoding of an ESD_EV_CAN_ERROR_EXT event message (which
> > > simply is a rx_msg with some dedicated data).
> > > 
> > > Suggested-by: Marc Kleine-Budde <mkl@...gutronix.de>
> > > Link: https://lore.kernel.org/linux-can/20220621071152.ggyhrr5sbzvwpkpx@pengutronix.de/
> > > Signed-off-by: Frank Jungclaus <frank.jungclaus@....eu>
> > > ---
> > >  drivers/net/can/usb/esd_usb.c | 18 +++++++++++++-----
> > >  1 file changed, 13 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/net/can/usb/esd_usb.c b/drivers/net/can/usb/esd_usb.c
> > > index 09745751f168..f90bb2c0ba15 100644
> > > --- a/drivers/net/can/usb/esd_usb.c
> > > +++ b/drivers/net/can/usb/esd_usb.c
> > > @@ -127,7 +127,15 @@ struct rx_msg {
> > >         u8 dlc;
> > >         __le32 ts;
> > >         __le32 id; /* upper 3 bits contain flags */
> > > -       u8 data[8];
> > > +       union {
> > > +               u8 data[8];
> > > +               struct {
> > > +                       u8 status; /* CAN Controller Status */
> > > +                       u8 ecc;    /* Error Capture Register */
> > > +                       u8 rec;    /* RX Error Counter */
> > > +                       u8 tec;    /* TX Error Counter */
> > > +               } ev_can_err_ext;  /* For ESD_EV_CAN_ERROR_EXT */
> > > +       };
> > >  };
> > > 
> > >  struct tx_msg {
> > > @@ -229,10 +237,10 @@ static void esd_usb_rx_event(struct esd_usb_net_priv *priv,
> > >         u32 id = le32_to_cpu(msg->msg.rx.id) & ESD_IDMASK;
> > > 
> > >         if (id == ESD_EV_CAN_ERROR_EXT) {
> > > -               u8 state = msg->msg.rx.data[0];
> > > -               u8 ecc = msg->msg.rx.data[1];
> > > -               u8 rxerr = msg->msg.rx.data[2];
> > > -               u8 txerr = msg->msg.rx.data[3];
> > > +               u8 state = msg->msg.rx.ev_can_err_ext.status;
> > > +               u8 ecc = msg->msg.rx.ev_can_err_ext.ecc;
> > > +               u8 rxerr = msg->msg.rx.ev_can_err_ext.rec;
> > > +               u8 txerr = msg->msg.rx.ev_can_err_ext.tec;
> > 
> > I do not like how you have to write msg->msg.rx.something. I think it
> > would be better to make the union within struct esd_usb_msg anonymous:
> > 
> >   https://elixir.bootlin.com/linux/latest/source/drivers/net/can/usb/esd_usb.c#L169
> 
> Or maybe just declare esd_usb_msg as an union instead of a struct:
> 
>   union esd_usb_msg {
>           struct header_msg hdr;
>           struct version_msg version;
>           struct version_reply_msg version_reply;
>           struct rx_msg rx;
>           struct tx_msg tx;
>           struct tx_done_msg txdone;
>           struct set_baudrate_msg setbaud;
>           struct id_filter_msg filter;
>   };

Apart from the fact that this change would probably require several
dozen lines of code to be adjusted, I like the idea ;)