netdev - Re: [PATCH] net: can: Add support for aliases in CAN

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Date: Thu, 4 Jan 2024 17:19:40 +0000
From: Simon Horman <horms@...nel.org>
To: Bhavya Kapoor <b-kapoor@...com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-can@...r.kernel.org, mailhol.vincent@...adoo.fr,
	rcsekar@...sung.com, pabeni@...hat.com, kuba@...nel.org,
	edumazet@...gle.com, davem@...emloft.net, mkl@...gutronix.de,
	wg@...ndegger.com, vigneshr@...com, u-kumar1@...com
Subject: Re: [PATCH] net: can: Add support for aliases in CAN

On Tue, Jan 02, 2024 at 03:59:49PM +0530, Bhavya Kapoor wrote:
> When multiple CAN's are present, then names that are getting assigned
> changes after every boot even after providing alias in the device tree.
> Thus, Add support for implementing CAN aliasing so that names or
> alias for CAN will now be provided from device tree.
> 
> Signed-off-by: Bhavya Kapoor <b-kapoor@...com>

Hi Bhavya,

some minor feedback from my side.

...

> diff --git a/drivers/net/can/dev/dev.c b/drivers/net/can/dev/dev.c
> index 3a3be5cdfc1f..ed483c23ec79 100644
> --- a/drivers/net/can/dev/dev.c
> +++ b/drivers/net/can/dev/dev.c
> @@ -247,12 +247,14 @@ void can_setup(struct net_device *dev)
>  
>  /* Allocate and setup space for the CAN network device */
>  struct net_device *alloc_candev_mqs(int sizeof_priv, unsigned int echo_skb_max,
> -				    unsigned int txqs, unsigned int rxqs)
> +					unsigned int txqs, unsigned int rxqs,
> +					struct device *candev)
>  {
>  	struct can_ml_priv *can_ml;
>  	struct net_device *dev;
>  	struct can_priv *priv;
> -	int size;
> +	int size, aliasid;
> +	char devname[6] = "can%d";

nit: Please consider arranging local variables in Networking code
     in reverse xmas tree order - longest line to shortest.

>  
>  	/* We put the driver's priv, the CAN mid layer priv and the
>  	 * echo skb into the netdevice's priv. The memory layout for
> @@ -273,7 +275,14 @@ struct net_device *alloc_candev_mqs(int sizeof_priv, unsigned int echo_skb_max,
>  		size = ALIGN(size, sizeof(struct sk_buff *)) +
>  			echo_skb_max * sizeof(struct sk_buff *);
>  
> -	dev = alloc_netdev_mqs(size, "can%d", NET_NAME_UNKNOWN, can_setup,
> +	if (candev) {
> +		aliasid = of_alias_get_id(candev->of_node, "can");
> +		if (aliasid >= 0)
> +			snprintf(devname, sizeof(devname), "%s%d", "can", aliasid);

The size of devname is 6 bytes (can%d\0).
This means that snprintf() will truncate devname if alias is greater than 99.
Is this a concern?

If so, perhaps devname could be declared to be IFNAMSIZ bytes long?

Flagged by gcc-13 -Wformat-truncation

> +	}
> +	dev_dbg(candev, "Name of CAN assigned is : %s\n", devname);
> +
> +	dev = alloc_netdev_mqs(size, devname, NET_NAME_UNKNOWN, can_setup,
>  			       txqs, rxqs);
>  	if (!dev)
>  		return NULL;

...