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    Subjectlibata, devm_*, and MSI ?
    Tejun / Jeff,

    I am working on MSI support for sata_mv, and am trying to puzzle out
    exactly what the kernel expects for this. Looking at other drivers,
    both libata and otherwise, yields a variety of conflicting implementations.

    For starters, the MSI HOW-TO suggests that drivers must be careful
    to invoke pci_disable_msi() on module unload, but I don't see that
    happening anywhere in libata.

    Unless, Tejun, the devm_* routines automatically do this.. do they?

    Next, there's no mention of a need for invoking pci_intx() in the HOW-TO,
    yet some device drivers call it, and others do not.

    Eg. from ahci.c, we have this:

    if ((hpriv->flags & AHCI_HFLAG_NO_MSI) || pci_enable_msi(pdev))
    pci_intx(pdev, 1);

    Which agrees with the existing code in sata_mv:

    if (msi && pci_enable_msi(pdev))
    pci_intx(pdev, 1);

    Which seems to call pci_intx() only when MSI is *not* used. Fine.
    But then in sata_vsc.c, we do sort of the opposite:

    if (pci_enable_msi(pdev) == 0)
    pci_intx(pdev, 0);

    Either that one is wrong, or pci_intx() is unnecessary in all cases.
    Again, the MSI HOW-TO doesn't even mention this routine.

    Looking through the network drivers, it seems that some of them
    do the pci_intx(pdev,1) call for the cases where pci_enable_msi() fails,
    similar to ahci.c and sata_mv.c.

    But not all of them do that.

    Perhaps somebody from the PCI side of things might enlighten us all.

    Thanks





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