netdev - Re: [PATCH net-next v7 1/8] bnxt_en: Add auxiliary driver support

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Date:   Fri, 13 Jan 2023 22:10:42 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ajit Khaparde <ajit.khaparde@...adcom.com>
Cc:     andrew.gospodarek@...adcom.com, davem@...emloft.net,
        edumazet@...gle.com, jgg@...pe.ca, leon@...nel.org,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        michael.chan@...adcom.com, netdev@...r.kernel.org,
        pabeni@...hat.com, selvin.xavier@...adcom.com,
        Leon Romanovsky <leonro@...dia.com>
Subject: Re: [PATCH net-next v7 1/8] bnxt_en: Add auxiliary driver support

On Thu, 12 Jan 2023 12:29:32 -0800 Ajit Khaparde wrote:
> Add auxiliary driver support.
> An auxiliary device will be created if the hardware indicates
> support for RDMA.
> The bnxt_ulp_probe() function has been removed and a new
> bnxt_rdma_aux_device_add() function has been added.
> The bnxt_free_msix_vecs() and bnxt_req_msix_vecs() will now hold
> the RTNL lock when they call the bnxt_close_nic()and bnxt_open_nic()
> since the device close and open need to be protected under RTNL lock.
> The operations between the bnxt_en and bnxt_re will be protected
> using the en_ops_lock.
> This will be used by the bnxt_re driver in a follow-on patch
> to create ROCE interfaces.

> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -13178,6 +13178,9 @@ static void bnxt_remove_one(struct pci_dev *pdev)
>  	struct net_device *dev = pci_get_drvdata(pdev);
>  	struct bnxt *bp = netdev_priv(dev);
>  
> +	bnxt_rdma_aux_device_uninit(bp);
> +	bnxt_aux_dev_free(bp);

You still free bp->aux_dev synchronously..

> +void bnxt_aux_dev_free(struct bnxt *bp)
> +{
> +	kfree(bp->aux_dev);

.. here. Which is called on .remove of the PCI device.

> +	bp->aux_dev = NULL;
> +}
> +
> +static struct bnxt_aux_dev *bnxt_aux_dev_alloc(struct bnxt *bp)
> +{
> +	return kzalloc(sizeof(struct bnxt_aux_dev), GFP_KERNEL);
> +}
> +
> +void bnxt_rdma_aux_device_uninit(struct bnxt *bp)
> +{
> +	struct bnxt_aux_dev *bnxt_adev;
> +	struct auxiliary_device *adev;
> +
> +	/* Skip if no auxiliary device init was done. */
> +	if (!(bp->flags & BNXT_FLAG_ROCE_CAP))
> +		return;
> +
> +	bnxt_adev = bp->aux_dev;
> +	adev = &bnxt_adev->aux_dev;
> +	auxiliary_device_delete(adev);
> +	auxiliary_device_uninit(adev);
> +	if (bnxt_adev->id >= 0)
> +		ida_free(&bnxt_aux_dev_ids, bnxt_adev->id);
> +}
> +
> +static void bnxt_aux_dev_release(struct device *dev)
> +{
> +	struct bnxt_aux_dev *bnxt_adev =
> +		container_of(dev, struct bnxt_aux_dev, aux_dev.dev);
> +	struct bnxt *bp = netdev_priv(bnxt_adev->edev->net);
> +
> +	bnxt_adev->edev->en_ops = NULL;
> +	kfree(bnxt_adev->edev);

And yet the reference counted "release" function accesses the bp->adev
like it must exist.

This seems odd to me - why do we need refcounting on devices at all 
if we can free them synchronously? To be clear - I'm not sure this is
wrong, just seems odd.

> +	bnxt_adev->edev = NULL;
> +	bp->edev = NULL;
> +}