Re: [PATCH v3 01/25] PCI: Add PCI_ERROR_RESPONSE and it's related definitions
From: Pali Rohár <pali@kernel.org>
Date: 2021-10-21 16:08:44
Also in:
linux-hyperv, linux-mediatek, linux-pci, linux-renesas-soc, linux-rockchip, linux-samsung-soc, linuxppc-dev, lkml
On Thursday 21 October 2021 20:37:26 Naveen Naidu wrote:
An 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 SET_PCI_ERROR_RESPONSE and RESPONSE_IS_PCI_ERROR to make the code more readable. Suggested-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Naveen Naidu <redacted>
Reviewed-by: Pali Rohár <pali@kernel.org>
quoted hunk ↗ jump to hunk
--- include/linux/pci.h | 9 +++++++++ 1 file changed, 9 insertions(+)diff --git a/include/linux/pci.h b/include/linux/pci.h index cd8aa6fce204..689c8277c584 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h@@ -154,6 +154,15 @@ enum pci_interrupt_pin { /* The number of legacy PCI INTx interrupts */ #define PCI_NUM_INTX 4 +/* + * Reading from a device that doesn't respond typically returns ~0. A + * successful read from a device may also return ~0, so you need additional + * information to reliably identify errors. + */ +#define PCI_ERROR_RESPONSE (~0ULL) +#define SET_PCI_ERROR_RESPONSE(val) (*(val) = ((typeof(*(val))) PCI_ERROR_RESPONSE)) +#define RESPONSE_IS_PCI_ERROR(val) ((val) == ((typeof(val)) PCI_ERROR_RESPONSE)) + /* * pci_power_t values must match the bits in the Capabilities PME_Support * and Control/Status PowerState fields in the Power Management capability.-- 2.25.1
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