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    SubjectRe: [EXT] Re: [PATCH v16 7/7] PCI: endpoint: pci-epf-vntb: fix sparse build warning at ntb->reg
    On Wed, Dec 14, 2022 at 12:49:15AM +0000, Frank Li wrote:
    > >
    > > On Wed, Nov 02, 2022 at 10:10:14AM -0400, Frank Li wrote:
    > > > From: Frank Li <frank.li@nxp.com>
    > > >
    > > > pci-epf-vntb.c:1128:33: sparse: expected void [noderef] __iomem
    > > *base
    > > > pci-epf-vntb.c:1128:33: sparse: got struct epf_ntb_ctrl *reg
    > > >
    > > > Add __iomem type convert in vntb_epf_peer_spad_read() and
    > > > vntb_epf_peer_spad_write().
    > >
    > > I don't understand all the bits and pieces here, but I'm a little
    > > dubious about adding all these "(void __iomem *)"casts. There are
    > > very few of them in drivers/pci/, and I doubt this driver is so unique
    > > that it needs them.
    >
    > sparse compiler report warning without cast. I write it at commit message.

    As a matter of fact, I did read your commit message. My point is that
    I don't think littering the code with casts is the best solution. I
    wrote more details below; please read the entire email.

    > > > @@ -1121,7 +1121,7 @@ static u32 vntb_epf_spad_read(struct ntb_dev
    > > *ndev, int idx)
    > > > struct epf_ntb *ntb = ntb_ndev(ndev);
    > > > int off = ntb->reg->spad_offset, ct = ntb->reg->spad_count *
    > > sizeof(u32);
    > > > u32 val;
    > > > - void __iomem *base = ntb->reg;
    > > > + void __iomem *base = (void __iomem *)ntb->reg;
    > > >
    > > > val = readl(base + off + ct + idx * sizeof(u32));
    > > > return val;
    > > > @@ -1132,7 +1132,7 @@ static int vntb_epf_spad_write(struct ntb_dev
    > > *ndev, int idx, u32 val)
    > > > struct epf_ntb *ntb = ntb_ndev(ndev);
    > > > struct epf_ntb_ctrl *ctrl = ntb->reg;
    > > > int off = ctrl->spad_offset, ct = ctrl->spad_count * sizeof(u32);
    > > > - void __iomem *base = ntb->reg;
    > > > + void __iomem *base = (void __iomem *)ntb->reg;
    > > >
    > > > writel(val, base + off + ct + idx * sizeof(u32));
    > >
    > > These things look gratuitously different to begin with:
    > >
    > > int off = ntb->reg->spad_offset, ct = ntb->reg->spad_count * sizeof(u32);
    > > int off = ctrl->spad_offset, ct = ctrl->spad_count * sizeof(u32);
    > >
    > > They're doing the same thing, and they should do it the same way.
    > >
    > > Since db_data[] and db_offset[] are never referenced except to be
    > > initialized to zero, I'm guessing the point of vntb_epf_spad_read()
    > > and vntb_epf_spad_write() is to read/write things in those arrays?
    > >
    > > You access other things in ntb->reg directly by dereferencing a
    > > pointer, e.g.,
    > >
    > > ntb->reg->link_status |= LINK_STATUS_UP;
    > > addr = ntb->reg->addr;
    > > ctrl->command_status = COMMAND_STATUS_OK;
    > >
    > > Why don't you just compute the appropriate *index* and access the
    > > array directly instead of using readl() and writel()?
    > >
    > > Bjorn

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