linux-kernel - Re: [PATCH v3 15/15] can: grcan: Update echo skb handling to match variable length CANFD frame

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Message-ID: <20260123-jolly-orangutan-of-finesse-5a9bb3-mkl@pengutronix.de>
Date: Fri, 23 Jan 2026 15:17:32 +0100
From: Marc Kleine-Budde <mkl@...gutronix.de>
To: Arun Muthusamy <arun.muthusamy@...sler.com>
Cc: robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	mailhol@...nel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-can@...r.kernel.org
Subject: Re: [PATCH v3 15/15] can: grcan: Update echo skb handling to match
 variable length CANFD frame

On 22.01.2026 13:10:38, Arun Muthusamy wrote:
[...]

> @@ -1575,7 +1591,16 @@ static netdev_tx_t grcan_start_xmit(struct sk_buff *skb,
>  	 * can_put_echo_skb would be an error unless other measures are
>  	 * taken.
>  	 */
> -	can_put_echo_skb(skb, dev, slotindex, 0);
> +
> +	priv->echo_skb_idx = priv->next_echo_idx;
> +
> +	can_put_echo_skb(skb, dev, priv->next_echo_idx, 0);
> +
> +	/* Move to the next index in the echo skb buffer */
> +	priv->next_echo_idx = (priv->next_echo_idx + 1) % priv->can.echo_skb_max;
> +
> +	if (priv->can.echo_skb[priv->echo_skb_idx])
> +		netif_stop_queue(dev);

You also use "if (unlikely(space == 1)) netif_stop_queue(dev);", that
looks suspicious. Why have 2 independent ways to check if the TX queue
is full?

Marc

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