netdev - Re: [PATCH v2 3/6] pds_core: add new fwctl auxiliary

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Message-ID: <20250304160321.000038a0@huawei.com>
Date: Tue, 4 Mar 2025 16:03:21 +0800
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Shannon Nelson <shannon.nelson@....com>
CC: <jgg@...dia.com>, <andrew.gospodarek@...adcom.com>,
	<aron.silverton@...cle.com>, <dan.j.williams@...el.com>,
	<daniel.vetter@...ll.ch>, <dave.jiang@...el.com>, <dsahern@...nel.org>,
	<gregkh@...uxfoundation.org>, <hch@...radead.org>, <itayavr@...dia.com>,
	<jiri@...dia.com>, <kuba@...nel.org>, <lbloch@...dia.com>,
	<leonro@...dia.com>, <linux-cxl@...r.kernel.org>,
	<linux-rdma@...r.kernel.org>, <netdev@...r.kernel.org>, <saeedm@...dia.com>,
	<brett.creeley@....com>
Subject: Re: [PATCH v2 3/6] pds_core: add new fwctl auxiliary_device

On Fri, 28 Feb 2025 17:35:51 -0800
Shannon Nelson <shannon.nelson@....com> wrote:

> Add support for a new fwctl-based auxiliary_device for creating a
> channel for fwctl support into the AMD/Pensando DSC.
> 
> Signed-off-by: Shannon Nelson <shannon.nelson@....com>
Hi Shannon,

A few really minor comments inline from a fresh read through.

Thanks,

Jonathan

> ---
>  drivers/net/ethernet/amd/pds_core/auxbus.c |  3 +--
>  drivers/net/ethernet/amd/pds_core/core.c   |  7 +++++++
>  drivers/net/ethernet/amd/pds_core/core.h   |  1 +
>  drivers/net/ethernet/amd/pds_core/main.c   | 11 +++++++++++
>  include/linux/pds/pds_common.h             |  2 ++
>  5 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amd/pds_core/auxbus.c b/drivers/net/ethernet/amd/pds_core/auxbus.c
> index db950a9c9d30..ac6f76c161f2 100644
> --- a/drivers/net/ethernet/amd/pds_core/auxbus.c
> +++ b/drivers/net/ethernet/amd/pds_core/auxbus.c
> @@ -225,8 +225,7 @@ int pdsc_auxbus_dev_add(struct pdsc *cf, struct pdsc *pf,
>  	}
>  
>  	/* Verify that the type is supported and enabled.  It is not
> -	 * an error if there is no auxbus device support for this
> -	 * VF, it just means something else needs to happen with it.
> +	 * an error if there is no auxbus device support.

Comment feels a bit general. Is this no auxbus support for this device
or none at all in the kernel?

>  	 */
>  	vt_support = !!le16_to_cpu(pf->dev_ident.vif_types[vt]);
>  	if (!(vt_support &&

> diff --git a/drivers/net/ethernet/amd/pds_core/main.c b/drivers/net/ethernet/amd/pds_core/main.c
> index a3a68889137b..41575c7a148d 100644
> --- a/drivers/net/ethernet/amd/pds_core/main.c
> +++ b/drivers/net/ethernet/amd/pds_core/main.c
> @@ -265,6 +265,10 @@ static int pdsc_init_pf(struct pdsc *pdsc)
>  
>  	mutex_unlock(&pdsc->config_lock);
>  
> +	err = pdsc_auxbus_dev_add(pdsc, pdsc, PDS_DEV_TYPE_FWCTL, &pdsc->padev);
> +	if (err)
> +		goto err_out_stop;
> +
>  	dl = priv_to_devlink(pdsc);
>  	devl_lock(dl);
>  	err = devl_params_register(dl, pdsc_dl_params,
> @@ -297,6 +301,7 @@ static int pdsc_init_pf(struct pdsc *pdsc)
>  	devlink_params_unregister(dl, pdsc_dl_params,
>  				  ARRAY_SIZE(pdsc_dl_params));
>  err_out_stop:
> +	pdsc_auxbus_dev_del(pdsc, pdsc, &pdsc->padev);

This doesn't smell right (by which I mean I had to go look at the
implementation to be sure it wasn't a bug) In my ideal
world that should be obvious on a more local basis.
I'd expect a new label here. pdsc_auxbus_dev_add() should be and is
side effect free if it fails. That is it should not make sense
to call pdsc_auxbus_dev_del() if it fails.

It isn't a bug today as that becomes a noop due to
&pdsc->padev being NULL but that is a detail I shouldn't
ideally need to know when reading this code.

I'd put err_out_stop label here and rename previous
one to err_out_auxbus_del + replace the existing
goto err_out_stop; 
with
goto err_out_auxbus_del;

>  	pdsc_stop(pdsc);
>  err_out_teardown:
>  	pdsc_teardown(pdsc, PDSC_TEARDOWN_REMOVING);
> @@ -427,6 +432,7 @@ static void pdsc_remove(struct pci_dev *pdev)
>  		 * shut themselves down.
>  		 */
>  		pdsc_sriov_configure(pdev, 0);
> +		pdsc_auxbus_dev_del(pdsc, pdsc, &pdsc->padev);
>  
>  		timer_shutdown_sync(&pdsc->wdtimer);
>  		if (pdsc->wq)
> @@ -485,6 +491,8 @@ static void pdsc_reset_prepare(struct pci_dev *pdev)
>  		if (!IS_ERR(pf))
>  			pdsc_auxbus_dev_del(pdsc, pf,
>  					    &pf->vfs[pdsc->vf_id].padev);
> +	} else {
> +		pdsc_auxbus_dev_del(pdsc, pdsc, &pdsc->padev);
>  	}
>  
>  	pdsc_unmap_bars(pdsc);
> @@ -531,6 +539,9 @@ static void pdsc_reset_done(struct pci_dev *pdev)
>  		if (!IS_ERR(pf))
>  			pdsc_auxbus_dev_add(pdsc, pf, PDS_DEV_TYPE_VDPA,
>  					    &pf->vfs[pdsc->vf_id].padev);
> +	} else {
> +		pdsc_auxbus_dev_add(pdsc, pdsc, PDS_DEV_TYPE_FWCTL,
> +				    &pdsc->padev);
>  	}
>  }