netdev - Re: [PATCH v2 01/12] can: Add LIN bus as CAN abstraction

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Message-ID: <20240504124904.GJ3167983@kernel.org>
Date: Sat, 4 May 2024 13:49:04 +0100
From: Simon Horman <horms@...nel.org>
To: Christoph Fritz <christoph.fritz@...dev.de>
Cc: Oliver Hartkopp <socketcan@...tkopp.net>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Vincent Mailhol <mailhol.vincent@...adoo.fr>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	Benjamin Tissoires <bentiss@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Sebastian Reichel <sre@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Andreas Lauser <andreas.lauser@...cedes-benz.com>,
	Jonathan Corbet <corbet@....net>,
	Pavel Pisa <pisa@....felk.cvut.cz>, linux-can@...r.kernel.org,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-input@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 01/12] can: Add LIN bus as CAN abstraction

On Thu, May 02, 2024 at 09:55:23AM +0200, Christoph Fritz wrote:
> This patch adds a LIN (local interconnect network) bus abstraction on
> top of CAN.  It is a glue driver adapting CAN on one side while offering
> LIN abstraction on the other side. So that upcoming LIN device drivers
> can make use of it.
> 
> Tested-by: Andreas Lauser <andreas.lauser@...cedes-benz.com>
> Signed-off-by: Christoph Fritz <christoph.fritz@...dev.de>

...

> diff --git a/drivers/net/can/lin.c b/drivers/net/can/lin.c

...

> +struct lin_device *register_lin(struct device *dev,
> +				const struct lin_device_ops *ldops)
> +{
> +	struct net_device *ndev;
> +	struct lin_device *ldev;
> +	int ret;
> +
> +	if (!ldops || !ldops->ldo_tx || !ldops->update_bitrate  ||
> +	    !ldops->ldo_open || !ldops->ldo_stop) {
> +		netdev_err(ndev, "missing mandatory lin_device_ops\n");

Hi Christoph,

The line above uses ndev, but ndev is not initialised
until a few lines further down.

Flagged by Smatch.

> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	ndev = alloc_candev(sizeof(struct lin_device), 1);
> +	if (!ndev)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ldev = netdev_priv(ndev);
> +
> +	ldev->ldev_ops = ldops;
> +	ndev->netdev_ops = &lin_netdev_ops;
> +	ndev->flags |= IFF_ECHO;
> +	ndev->mtu = CANFD_MTU;
> +	ldev->can.bittiming.bitrate = LIN_DEFAULT_BAUDRATE;
> +	ldev->can.ctrlmode = CAN_CTRLMODE_LIN;
> +	ldev->can.ctrlmode_supported = 0;
> +	ldev->can.bitrate_const = lin_bitrate;
> +	ldev->can.bitrate_const_cnt = ARRAY_SIZE(lin_bitrate);
> +	ldev->can.do_set_bittiming = lin_set_bittiming;
> +	ldev->ndev = ndev;
> +	ldev->dev = dev;
> +
> +	SET_NETDEV_DEV(ndev, dev);
> +
> +	ret = lin_set_bittiming(ndev);
> +	if (ret) {
> +		netdev_err(ndev, "set bittiming failed\n");
> +		goto exit_candev;
> +	}
> +
> +	ret = register_candev(ndev);
> +	if (ret)
> +		goto exit_candev;
> +
> +	ldev->lin_ids_kobj = kobject_create_and_add("lin_ids", &ndev->dev.kobj);
> +	if (!ldev->lin_ids_kobj) {
> +		netdev_err(ndev, "Failed to create sysfs directory\n");
> +		ret = -ENOMEM;
> +		goto exit_unreg;
> +	}
> +
> +	ret = lin_create_sysfs_id_files(ndev);
> +	if (ret) {
> +		netdev_err(ndev, "Failed to create sysfs entry: %d\n", ret);
> +		goto exit_kobj_put;
> +	}
> +
> +	/* Using workqueue as tx over USB/SPI/... may sleep */
> +	ldev->wq = alloc_workqueue(dev_name(dev), WQ_FREEZABLE | WQ_MEM_RECLAIM,
> +				   0);
> +	if (!ldev->wq)
> +		goto exit_rm_files;

The goto above will result in: return ERR_PTR(ret)
But ret is 0 here. Should it be set to a negative error value?

Also flagged by Smatch.

> +
> +	INIT_WORK(&ldev->tx_work, lin_tx_work_handler);
> +
> +	netdev_info(ndev, "LIN initialized.\n");
> +
> +	return ldev;
> +
> +exit_rm_files:
> +	lin_remove_sysfs_id_files(ndev);
> +exit_kobj_put:
> +	kobject_put(ldev->lin_ids_kobj);
> +exit_unreg:
> +	unregister_candev(ndev);
> +exit_candev:
> +	free_candev(ndev);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(register_lin);

...