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

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Date:   Tue, 20 Dec 2022 14:27:17 +0900
From:   Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To:     Frank Jungclaus <frank.jungclaus@....eu>
Cc:     linux-can@...r.kernel.org, Marc Kleine-Budde <mkl@...gutronix.de>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Stefan Mätje <stefan.maetje@....eu>,
        netdev@...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

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

That said, this is not a criticism of this patch but more something to
be addressed in a separate clean-up patch.

>                 netdev_dbg(priv->netdev,
>                            "CAN_ERR_EV_EXT: dlc=%#02x state=%02x ecc=%02x rec=%02x tec=%02x\n",
> --
> 2.25.1
>