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Date: Thu, 3 Apr 2014 17:06:32 -0700
Message-ID: <CAE9FiQUHC4jPJttUpChAALd6zubbQQEZ9wRc329Lv5QAXGOUKw@mail.gmail.com>
Subject: Re: Coverity CID 142811: pci_set_vga_state() operands don't affect result
From: Yinghai Lu <yinghai@kernel.org>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Dave Airlie <airlied@redhat.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
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On Thu, Apr 3, 2014 at 1:43 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> Coverity complains about this in drivers/pci/pci.c:
>
> CID 142811 (#1 of 1): Operands don't affect result (CONSTANT_EXPRESSION_RESULT)
> result_independent_of_operands: flags & (2U /* 1 << 1 */) &
> (command_bits & 4294967292U /* ~(1 | 2) */) is always 0 regardless of
> the values of its operands. This occurs as the logical operand of if.
>
> 4128        WARN_ON((flags & PCI_VGA_STATE_CHANGE_DECODES) &
> (command_bits & ~(PCI_COMMAND_IO|PCI_COMMAND_MEMORY)));
>
> This is a result of 3448a19da479 "vgaarb: use bridges to control VGA
> routing where possible."
>
> I wonder if that middle "&" was intended to be "&&"?

must be. otherwise always get 0.