linux-kernel - Re: [PATCH][next] PCI: Fix ternary operator that never returns 0

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Message-ID: <b0d6ea82-c979-447a-9e63-0dbdbf23d411@stanley.mountain>
Date: Fri, 17 Jan 2025 08:25:51 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: David Laight <david.laight.linux@...il.com>
Cc: Colin Ian King <colin.i.king@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	linux-pci@...r.kernel.org, kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] PCI: Fix ternary operator that never returns 0

On Thu, Jan 16, 2025 at 10:49:44PM +0000, David Laight wrote:
> On Thu, 16 Jan 2025 17:20:19 +0000
> Colin Ian King <colin.i.king@...il.com> wrote:
> 
> > The left hand size of the ? operator is always true because of the addition
> > of PCIE_STD_NUM_TLP_HEADERLOG and so dev->eetlp_prefix_max is always being
> > returned and the 0 is never returned (dead code). Fix this by adding the
> > required parentheses around the ternary operator.
> > 
> > Fixes: 00048c2d5f11 ("PCI: Add TLP Prefix reading to pcie_read_tlp_log()")
> > Signed-off-by: Colin Ian King <colin.i.king@...il.com>
> > ---
> >  drivers/pci/pcie/tlp.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/pcie/tlp.c b/drivers/pci/pcie/tlp.c
> > index 9b9e348fb1a0..0860b5da837f 100644
> > --- a/drivers/pci/pcie/tlp.c
> > +++ b/drivers/pci/pcie/tlp.c
> > @@ -22,8 +22,8 @@
> >  unsigned int aer_tlp_log_len(struct pci_dev *dev, u32 aercc)
> >  {
> >  	return PCIE_STD_NUM_TLP_HEADERLOG +
> > -	       (aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
> > -	       dev->eetlp_prefix_max : 0;
> > +	       ((aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
> 
> You can remove the extra set around the condition itself as well.
> They are a good hint the writer doesn't know their operator
> precedences :-)

Please leave them as-is...  I obsolutely do not remember the operator
precedences between & and ? and I have to look it up every time I see
it.

regards,
dan carpenter