linux-kernel - Re: [PATCH net-next v18 1/1] mctp pcc: Implement MCTP over PCC Transport

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Message-ID: <20250224181117.21ad7ab1@kernel.org>
Date: Mon, 24 Feb 2025 18:11:17 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: admiyo@...amperecomputing.com
Cc: Jeremy Kerr <jk@...econstruct.com.au>, Matt Johnston
 <matt@...econstruct.com.au>, Andrew Lunn <andrew+netdev@...n.ch>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Sudeep Holla <sudeep.holla@....com>, Jonathan
 Cameron <Jonathan.Cameron@...wei.com>, Huisong Li <lihuisong@...wei.com>
Subject: Re: [PATCH net-next v18 1/1] mctp pcc: Implement MCTP over PCC
 Transport

On Thu, 20 Feb 2025 13:34:10 -0500 admiyo@...amperecomputing.com wrote:
> +MANAGEMENT COMPONENT TRANSPORT PROTOCOL (MCTP) over PCC (MCTP-PCC) Driver
> +M:	Adam Young <admiyo@...amperecomputing.com>
> +L:	netdev@...r.kernel.org

You can drop the L:, AFAIK, it's going to be inherited from next layer
of entries.

> +S:	Maintained
> +F:	drivers/net/mctp/mctp-pcc.c
> +

> +static netdev_tx_t mctp_pcc_tx(struct sk_buff *skb, struct net_device *ndev)
> +{
> +	struct mctp_pcc_ndev *mpnd = netdev_priv(ndev);
> +	struct mctp_pcc_hdr  *mctp_pcc_header;
> +	void __iomem *buffer;
> +	unsigned long flags;
> +	int len = skb->len;
> +
> +	dev_dstats_tx_add(ndev, len);

To be safe you should call:

	if (skb_cow_head(skb, ..

to make sure skb isn't a clone.

> +	spin_lock_irqsave(&mpnd->lock, flags);
> +	mctp_pcc_header = skb_push(skb, sizeof(struct mctp_pcc_hdr));
> +	buffer = mpnd->outbox.chan->shmem;
> +	mctp_pcc_header->signature = cpu_to_le32(PCC_MAGIC | mpnd->outbox.index);
> +	mctp_pcc_header->flags = cpu_to_le32(PCC_HEADER_FLAGS);
> +	memcpy(mctp_pcc_header->mctp_signature, MCTP_SIGNATURE,
> +	       MCTP_SIGNATURE_LENGTH);
> +	mctp_pcc_header->length = cpu_to_le32(len + MCTP_SIGNATURE_LENGTH);
> +
> +	memcpy_toio(buffer, skb->data, skb->len);
> +	mpnd->outbox.chan->mchan->mbox->ops->send_data(mpnd->outbox.chan->mchan,
> +						    NULL);
> +	spin_unlock_irqrestore(&mpnd->lock, flags);
> +
> +	dev_consume_skb_any(skb);
> +	return NETDEV_TX_OK;
> +}

> +static int mctp_pcc_driver_add(struct acpi_device *acpi_dev)
> +{
> +	struct mctp_pcc_lookup_context context = {0, 0, 0};
> +	struct mctp_pcc_ndev *mctp_pcc_ndev;
> +	struct device *dev = &acpi_dev->dev;
> +	struct net_device *ndev;
> +	acpi_handle dev_handle;
> +	acpi_status status;
> +	int mctp_pcc_mtu;
> +	char name[32];
> +	int rc;
> +
> +	dev_dbg(dev, "Adding mctp_pcc device for HID %s\n",
> +		acpi_device_hid(acpi_dev));
> +	dev_handle = acpi_device_handle(acpi_dev);
> +	status = acpi_walk_resources(dev_handle, "_CRS", lookup_pcct_indices,
> +				     &context);
> +	if (!ACPI_SUCCESS(status)) {
> +		dev_err(dev, "FAILURE to lookup PCC indexes from CRS\n");
> +		return -EINVAL;
> +	}
> +
> +	//inbox initialization

Prefer C comments, please.

> +	snprintf(name, sizeof(name), "mctpipcc%d", context.inbox_index);
> +	ndev = alloc_netdev(sizeof(struct mctp_pcc_ndev), name, NET_NAME_ENUM,

Enum means the kernel assigns the ID, you're fully formatting the name
in the driver based on fixed device attributes, so NET_NAME_PREDICTABLE

> +			    mctp_pcc_setup);
> +	if (!ndev)
> +		return -ENOMEM;

> +	return devm_add_action_or_reset(dev, mctp_cleanup_netdev, ndev);
> +cleanup_netdev:

rename the label to free_netdev, please, to match with the first action

> +	free_netdev(ndev);
> +	return rc;
> +}
-- 
pw-bot: cr