netdev - Re: [PATCH v2] net: Add mhi-net driver

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Date:   Tue, 13 Oct 2020 09:41:32 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Loic Poulain <loic.poulain@...aro.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        manivannan.sadhasivam@...aro.org, hemantk@...eaurora.org
Subject: Re: [PATCH v2] net: Add mhi-net driver

On Mon, 12 Oct 2020 17:26:03 +0200 Loic Poulain wrote:
> This patch adds a new network driver implementing MHI transport for
> network packets. Packets can be in any format, though QMAP (rmnet)
> is the usual protocol (flow control + PDN mux).
> 
> It support two MHI devices, IP_HW0 which is, the path to the IPA
> (IP accelerator) on qcom modem, And IP_SW0 which is the software
> driven IP path (to modem CPU).
> 
> Signed-off-by: Loic Poulain <loic.poulain@...aro.org>

> +static void mhi_net_rx_refill_work(struct work_struct *work)
> +{
> +	struct mhi_net_dev *mhi_netdev = container_of(work, struct mhi_net_dev,
> +						      rx_refill.work);
> +	struct net_device *ndev = mhi_netdev->ndev;
> +	struct mhi_device *mdev = mhi_netdev->mdev;
> +	struct sk_buff *skb;
> +	int err;
> +
> +	do {
> +		skb = netdev_alloc_skb(ndev, READ_ONCE(ndev->mtu));
> +		if (unlikely(!skb))
> +			break;
> +
> +		err = mhi_queue_skb(mdev, DMA_FROM_DEVICE, skb, ndev->mtu,
> +				    MHI_EOT);
> +		if (err) {
> +			if (unlikely(err != -ENOMEM)) {
> +				net_err_ratelimited("%s: Failed to queue RX buf (%d)\n",
> +						    ndev->name, err);
> +			}

nit: no need for parens here

> +			kfree_skb(skb);
> +			break;
> +		}
> +
> +		atomic_inc_return(&mhi_netdev->stats.rx_queued);
> +	} while (1);
> +
> +	/* If we're still starved of rx buffers, reschedule latter */
> +	if (unlikely(!atomic_read(&mhi_netdev->stats.rx_queued)))
> +		schedule_delayed_work(&mhi_netdev->rx_refill, HZ / 2);
> +}

> +	/* Start MHI channels */
> +	err = mhi_prepare_for_transfer(mhi_dev);
> +	if (err)
> +		goto out_err;
> +
> +	err = register_netdev(ndev);
> +	if (err)
> +		goto out_err;
> +
> +	return 0;

no need to

	mhi_unprepare_from_transfer(mhi_netdev->mdev);

here when coming from register_netdev() failure?

> +out_err:
> +	free_netdev(ndev);
> +	return err;
> +}
> +
> +static void mhi_net_remove(struct mhi_device *mhi_dev)
> +{
> +	struct mhi_net_dev *mhi_netdev = dev_get_drvdata(&mhi_dev->dev);
> +
> +	unregister_netdev(mhi_netdev->ndev);
> +
> +	mhi_unprepare_from_transfer(mhi_netdev->mdev);
> +
> +	free_netdev(mhi_netdev->ndev);
> +}