netdev - Re: [PATCH v4 01/14] net: ionic: Create an auxiliary device for rdma driver

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Message-ID: <7044823e-c263-4789-b83c-ecb1eccde04f@wanadoo.fr>
Date: Fri, 1 Aug 2025 23:15:24 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Abhijit Gangurde <abhijit.gangurde@....com>, shannon.nelson@....com,
 brett.creeley@....com, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, corbet@....net, jgg@...pe.ca,
 leon@...nel.org, andrew+netdev@...n.ch
Cc: allen.hubbe@....com, nikhil.agarwal@....com, linux-rdma@...r.kernel.org,
 netdev@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 01/14] net: ionic: Create an auxiliary device for rdma
 driver

Le 23/07/2025 à 19:31, Abhijit Gangurde a écrit :
> To support RDMA capable ethernet device, create an auxiliary device in
> the ionic Ethernet driver. The RDMA device is modeled as an auxiliary
> device to the Ethernet device.

...

> +static DEFINE_IDA(aux_ida);
> +
> +static void ionic_auxbus_release(struct device *dev)
> +{
> +	struct ionic_aux_dev *ionic_adev;
> +
> +	ionic_adev = container_of(dev, struct ionic_aux_dev, adev.dev);
> +	kfree(ionic_adev);
> +}
> +
> +int ionic_auxbus_register(struct ionic_lif *lif)

The 2 places that uses thus function don't check its error code.

> +{
> +	struct ionic_aux_dev *ionic_adev;
> +	struct auxiliary_device *aux_dev;
> +	int err, id;
> +
> +	if (!(le64_to_cpu(lif->ionic->ident.lif.capabilities) & IONIC_LIF_CAP_RDMA))
> +		return 0;
> +
> +	ionic_adev = kzalloc(sizeof(*ionic_adev), GFP_KERNEL);
> +	if (!ionic_adev)
> +		return -ENOMEM;
> +
> +	aux_dev = &ionic_adev->adev;
> +
> +	id = ida_alloc_range(&aux_ida, 0, INT_MAX, GFP_KERNEL);

Nitpick: why not just: ida_alloc(&aux_ida, GFP_KERNEL);

> +	if (id < 0) {
> +		dev_err(lif->ionic->dev, "Failed to allocate aux id: %d\n",
> +			id);
> +		err = id;
> +		goto err_adev_free;
> +	}
> +
> +	aux_dev->id = id;
> +	aux_dev->name = "rdma";
> +	aux_dev->dev.parent = &lif->ionic->pdev->dev;
> +	aux_dev->dev.release = ionic_auxbus_release;
> +	ionic_adev->lif = lif;
> +	err = auxiliary_device_init(aux_dev);
> +	if (err) {
> +		dev_err(lif->ionic->dev, "Failed to initialize %s aux device: %d\n",
> +			aux_dev->name, err);
> +		goto err_ida_free;
> +	}
> +
> +	err = auxiliary_device_add(aux_dev);
> +	if (err) {
> +		dev_err(lif->ionic->dev, "Failed to add %s aux device: %d\n",
> +			aux_dev->name, err);
> +		goto err_aux_uninit;
> +	}
> +
> +	lif->ionic_adev = ionic_adev;
> +
> +	return 0;
> +
> +err_aux_uninit:
> +	auxiliary_device_uninit(aux_dev);

I think a return err; is missing here, because, IMOH, 
auxiliary_device_uninit() will call put_device() that will trigger 
ionic_auxbus_release(). So kfree(ionic_adev) would be called twice.

I also think that ida_free() should also be ionic_auxbus_release() (just 
a guess, not checked in details)

> +err_ida_free:
> +	ida_free(&aux_ida, id);
> +err_adev_free:
> +	kfree(ionic_adev);
> +
> +	return err;
> +}
> +
> +void ionic_auxbus_unregister(struct ionic_lif *lif)
> +{
> +	struct auxiliary_device *aux_dev;
> +	int id;
> +
> +	mutex_lock(&lif->adev_lock);
> +	if (!lif->ionic_adev)
> +		goto out;
> +
> +	aux_dev = &lif->ionic_adev->adev;
> +	id = aux_dev->id;
> +
> +	auxiliary_device_delete(aux_dev);
> +	auxiliary_device_uninit(aux_dev);
> +	ida_free(&aux_ida, id);
> +
> +	lif->ionic_adev = NULL;
> +
> +out:
> +	mutex_unlock(&lif->adev_lock);
> +}

...

CJ