linux-kernel - re: PCI: Add TLP Prefix reading to pcie_read_tlp

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Message-ID: <a2f75da3-7065-4592-aa64-5e3590ce5f91@gmail.com>
Date: Thu, 16 Jan 2025 15:57:05 +0000
From: "Colin King (gmail)" <colin.i.king@...il.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
 Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
 Oliver O'Halloran <oohall@...il.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>, linux-pci@...r.kernel.org,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: re: PCI: Add TLP Prefix reading to pcie_read_tlp_log()

Hi,

Static analysis shows there is a potential issue in the following commit:

commit 00048c2d5f113bb4e82a0a30dfc4ee12590b81f5
Author: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Date:   Tue Jan 14 19:08:39 2025 +0200

     PCI: Add TLP Prefix reading to pcie_read_tlp_log()


The issue is described as follows:

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;
}


static analysis is warning that the left hand size of the ? operator is 
always true and so dev->eetlp_prefix_max is always being returned and 
the 0 is never returned (dead code).

I suspect the expected behaviour is as follows:

         return PCIE_STD_NUM_TLP_HEADERLOG +
                ((aercc & PCI_ERR_CAP_PREFIX_LOG_PRESENT) ?
                dev->eetlp_prefix_max : 0);

..I'm reluctant to send a fix in case this is not the original intention.

Colin

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