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Date:   Tue, 27 Oct 2020 11:37:01 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Shawn Lin <shawn.lin@rock-chips.com>
Cc:     linux-pci@vger.kernel.org
Subject: Re: pcie-rockchip-ep.c coverity issue #1437163
Message-ID: <20201027163701.GA184393@bjorn-Precision-5520>
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On Tue, Oct 27, 2020 at 11:16:38AM -0500, Bjorn Helgaas wrote:
> Hi Shawn,
> 
> Please take a look at this issue reported by Coverity:
> 
> 332 static int rockchip_pcie_ep_get_msi(struct pci_epc *epc, u8 fn)
> 333 {
> 334        struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
> 335        struct rockchip_pcie *rockchip = &ep->rockchip;
> 336        u16 flags;
> 337
> 338        flags = rockchip_pcie_read(rockchip,
> 339                                   ROCKCHIP_PCIE_EP_FUNC_BASE(fn) +
> 340                                   ROCKCHIP_PCIE_EP_MSI_CTRL_REG);
> 
> CID 1437163 (#2 of 2): Operands don't affect result
> (CONSTANT_EXPRESSION_RESULT) result_independent_of_operands: flags &
> (65536UL /* 1UL << 16 */) is always 0 regardless of the values of its
> operands. This occurs as the logical operand of !.
> 
> 341        if (!(flags & ROCKCHIP_PCIE_EP_MSI_CTRL_ME))
> 342                return -EINVAL;

The same issue also occurs in rockchip_pcie_ep_send_msi_irq()
(Coverity issue #143765 for that one).