On Fri, Oct 15, 2021 at 07:58:16PM +0530, 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@xxxxxxxxxx>
> Signed-off-by: Naveen Naidu <naveennaidu479@xxxxxxxxx>
> ---
> include/linux/pci.h | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index cd8aa6fce204..928c589bb5c4 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))
No reason for val to be a pointer.
Also, macro parameters need () around them. val could be an expression
like 'ptr + 1' which would blow up for example.
> +
> /*
> * 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
>
>
