linux-kernel - Re: [PATCH] Octeontx2-af: Fix pci_alloc_irq

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Message-ID: <aO9dClea18rk9Kdx@horms.kernel.org>
Date: Wed, 15 Oct 2025 09:36:26 +0100
From: Simon Horman <horms@...nel.org>
To: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
Cc: Sunil Goutham <sgoutham@...vell.com>,
	Linu Cherian <lcherian@...vell.com>,
	Geetha sowjanya <gakula@...vell.com>,
	Jerin Jacob <jerinj@...vell.com>, hariprasad <hkelam@...vell.com>,
	Subbaraya Sundeep <sbhatta@...vell.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Nithya Mani <nmani@...vell.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, dan.carpenter@...aro.org,
	kernel-janitors@...r.kernel.org, error27@...il.com
Subject: Re: [PATCH] Octeontx2-af: Fix pci_alloc_irq_vectors() return value
 check

On Tue, Oct 14, 2025 at 03:50:47PM +0530, Harshit Mogalapalli wrote:
> Hi,
> 
> On 14/10/25 15:44, Harshit Mogalapalli wrote:
> > In cgx_probe() when pci_alloc_irq_vectors() fails the error value will
> > be negative and that check is sufficient.
> > 
> > 	err = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_MSIX);
> >          if (err < 0 || err != nvec) {
> >          	...
> > 	}
> > 
> > Remove the check which compares err with nvec.
> > 
> > Fixes: 1463f382f58d ("octeontx2-af: Add support for CGX link management")
> > Suggested-by: Paolo Abeni <pabeni@...hat.com>
> > Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> > ---
> > Only compile tested.
> > ---
> >   drivers/net/ethernet/marvell/octeontx2/af/cgx.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
> > index d374a4454836..f4d5a3c05fa4 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
> > @@ -1993,7 +1993,7 @@ static int cgx_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> >   	nvec = pci_msix_vec_count(cgx->pdev);
> >   	err = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_MSIX);
> > -	if (err < 0 || err != nvec) {
> > +	if (err < 0) {
> >   		dev_err(dev, "Request for %d msix vectors failed, err %d\n",
> >   			nvec, err);
> 
> 
> Now that I think about it more, maybe we want to error out when err != nvec
> as well ? In that case maybe the right thing to do is leave the check as is
> and set err = -EXYZ before goto ?
> 
> Thanks,
> Harshit>   		goto err_release_regions;

Hi Harshit,

My reading of the documentation of pci_alloc_irq_vectors() is that
Because nvec is passed as both the min and max desired vectors,
either nvecs will be allocated, or -ENOSPC will be returned.

Maybe it is worth adding a comment about that to patch description
or the code. But I think the code in this patch is correct.