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PCI: Add PCI_ERROR_RESPONSE and related definitions
A config or MMIO read from a PCI device that doesn't exist or doesn't respond causes a PCI error. There's no real data to return to satisfy the CPU read, so most hardware fabricates ~0 data. Add a PCI_ERROR_RESPONSE definition for that and use it where appropriate to make these checks consistent and easier to find. Also add helper definitions PCI_SET_ERROR_RESPONSE() and PCI_POSSIBLE_ERROR() to make the code more readable. Suggested-by: Bjorn Helgaas <bhelgaas@google.com> Link: https://lore.kernel.org/r/55563bf4dfc5d3fdc96695373c659d099bf175b1.1637243717.git.naveennaidu479@gmail.com Signed-off-by: Naveen Naidu <naveennaidu479@gmail.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Pali Rohár <pali@kernel.org>
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@ -154,6 +154,15 @@ enum pci_interrupt_pin {
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/* The number of legacy PCI INTx interrupts */
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#define PCI_NUM_INTX 4
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/*
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* Reading from a device that doesn't respond typically returns ~0. A
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* successful read from a device may also return ~0, so you need additional
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* information to reliably identify errors.
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*/
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#define PCI_ERROR_RESPONSE (~0ULL)
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#define PCI_SET_ERROR_RESPONSE(val) (*(val) = ((typeof(*(val))) PCI_ERROR_RESPONSE))
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#define PCI_POSSIBLE_ERROR(val) ((val) == ((typeof(val)) PCI_ERROR_RESPONSE))
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/*
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* pci_power_t values must match the bits in the Capabilities PME_Support
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* and Control/Status PowerState fields in the Power Management capability.
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