From 57bdeef4716689d9b0e3571034d65cf420f6efcd Mon Sep 17 00:00:00 2001 From: Naveen Naidu Date: Thu, 18 Nov 2021 19:33:11 +0530 Subject: PCI: Add PCI_ERROR_RESPONSE and related definitions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Link: https://lore.kernel.org/r/55563bf4dfc5d3fdc96695373c659d099bf175b1.1637243717.git.naveennaidu479@gmail.com Signed-off-by: Naveen Naidu Signed-off-by: Bjorn Helgaas Reviewed-by: Pali Rohár --- include/linux/pci.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux') diff --git a/include/linux/pci.h b/include/linux/pci.h index 18a75c8e615c..0ce26850470e 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 PCI_SET_ERROR_RESPONSE(val) (*(val) = ((typeof(*(val))) PCI_ERROR_RESPONSE)) +#define PCI_POSSIBLE_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. -- cgit v1.2.3