linux-kernel - Re: [PATCH v3 13/13] can: slcan: extend the protocol with CAN state info

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Date:   Mon, 13 Jun 2022 09:37:06 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org, michael@...rulasolutions.com,
        Amarula patchwork <linux-amarula@...rulasolutions.com>,
        Oliver Hartkopp <socketcan@...tkopp.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 13/13] can: slcan: extend the protocol with CAN state
 info

On 12.06.2022 23:39:27, Dario Binacchi wrote:
> It extends the protocol to receive the adapter CAN state changes
> (warning, busoff, etc.) and forward them to the netdev upper levels.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> 
> ---
> 
> Changes in v3:
> - Drop the patch "can: slcan: simplify the device de-allocation".
> - Add the patch "can: netlink: dump bitrate 0 if can_priv::bittiming.bitrate is -1U".
> 
> Changes in v2:
> - Continue error handling even if no skb can be allocated.
> 
>  drivers/net/can/slcan/slcan-core.c | 66 ++++++++++++++++++++++++++++++
>  1 file changed, 66 insertions(+)
> 
> diff --git a/drivers/net/can/slcan/slcan-core.c b/drivers/net/can/slcan/slcan-core.c
> index 48077edb9497..5ba1c141f942 100644
> --- a/drivers/net/can/slcan/slcan-core.c
> +++ b/drivers/net/can/slcan/slcan-core.c
> @@ -78,6 +78,9 @@ MODULE_PARM_DESC(maxdev, "Maximum number of slcan interfaces");
>  #define SLC_CMD_LEN 1
>  #define SLC_SFF_ID_LEN 3
>  #define SLC_EFF_ID_LEN 8
> +#define SLC_STATE_LEN 1
> +#define SLC_STATE_BE_RXCNT_LEN 3
> +#define SLC_STATE_BE_TXCNT_LEN 3
>  
>  struct slcan {
>  	struct can_priv         can;
> @@ -175,6 +178,67 @@ int slcan_enable_err_rst_on_open(struct net_device *ndev, bool on)
>    *			STANDARD SLCAN DECAPSULATION			 *
>    ************************************************************************/
>  
> +static void slc_bump_state(struct slcan *sl)
> +{
> +	struct net_device *dev = sl->dev;
> +	struct sk_buff *skb;
> +	struct can_frame *cf;
> +	char *cmd = sl->rbuff;
> +	u32 rxerr, txerr;
> +	enum can_state state, rx_state, tx_state;
> +
> +	if (*cmd != 's')
> +		return;

Checked by the caller?

> +
> +	cmd += SLC_CMD_LEN;
> +	switch (*cmd) {
> +	case 'a':
> +		state = CAN_STATE_ERROR_ACTIVE;
> +		break;
> +	case 'w':
> +		state = CAN_STATE_ERROR_WARNING;
> +		break;
> +	case 'p':
> +		state = CAN_STATE_ERROR_PASSIVE;
> +		break;
> +	case 'f':
> +		state = CAN_STATE_BUS_OFF;
> +		break;
> +	default:
> +		return;
> +	}
> +
> +	if (state == sl->can.state)
> +		return;
> +
> +	cmd += SLC_STATE_BE_RXCNT_LEN + 1;

Have you checked that you have received that much data?

> +	cmd[SLC_STATE_BE_TXCNT_LEN] = 0;
> +	if (kstrtou32(cmd, 10, &txerr))
> +		return;
> +
> +	*cmd = 0;
> +	cmd -= SLC_STATE_BE_RXCNT_LEN;
> +	if (kstrtou32(cmd, 10, &rxerr))
> +		return;

Why do you parse TX first and then RX?

> +
> +	skb = alloc_can_err_skb(dev, &cf);
> +
> +	if (skb) {
> +		cf->data[6] = txerr;
> +		cf->data[7] = rxerr;
> +	}
> +
> +	tx_state = txerr >= rxerr ? state : 0;
> +	rx_state = txerr <= rxerr ? state : 0;
> +	can_change_state(dev, skb ? cf : NULL, tx_state, rx_state);

alloc_can_err_skb() set cf to NULL if no skb can be allocated.

> +
> +	if (state == CAN_STATE_BUS_OFF)
> +		can_bus_off(dev);
> +
> +	if (skb)
> +		netif_rx(skb);
> +}
> +
>  static void slc_bump_err(struct slcan *sl)
>  {
>  	struct net_device *dev = sl->dev;
> @@ -378,6 +442,8 @@ static void slc_bump(struct slcan *sl)
>  		return slc_bump_frame(sl);
>  	case 'e':
>  		return slc_bump_err(sl);
> +	case 's':
> +		return slc_bump_state(sl);
>  	default:
>  		return;
>  	}
> -- 
> 2.32.0
> 
> 

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
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