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

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Message-ID: <20250116224944.283e14fb@pumpkin>
Date: Thu, 16 Jan 2025 22:49:44 +0000
From: David Laight <david.laight.linux@...il.com>
To: Colin Ian King <colin.i.king@...il.com>
Cc: 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, 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 :-)

	David

> +		dev->eetlp_prefix_max : 0);
>  }
>  
>  #ifdef CONFIG_PCIE_DPC