On Mon, Oct 11, 2021 at 11:08:32PM +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.
>
> Use SET_PCI_ERROR_RESPONSE() to set the error response and
> RESPONSE_IS_PCI_ERROR() to check the error response during hardware
> read.
>
> These definitions make error checks consistent and easier to find.
>
> Signed-off-by: Naveen Naidu <naveennaidu479@xxxxxxxxx>
> ---
> drivers/pci/access.c | 22 +++++++++++-----------
> 1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> index 46935695cfb9..e1954bbbd137 100644
> --- a/drivers/pci/access.c
> +++ b/drivers/pci/access.c
> @@ -81,7 +81,7 @@ int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
>
> addr = bus->ops->map_bus(bus, devfn, where);
> if (!addr) {
> - *val = ~0;
> + SET_PCI_ERROR_RESPONSE(val);
This to me doesn't look like kernel style. I'd rather see a define
replace just '~0', but I defer to Bjorn.
> return PCIBIOS_DEVICE_NOT_FOUND;
Neither does this using custom error codes rather than standard Linux
errno. I point this out as I that's were I'd start with the config
accessors. Though there are lots of occurrences so we'd need a way to do
this in manageable steps.
Can't we make PCI_OP_READ and PCI_USER_READ_CONFIG set the data value
and delete the drivers all doing this? Then we have 2 copies (in source)
rather than the many this series modifies. Though I'm not sure if there
are other cases of calling pci_bus.ops.read() which expect to get ~0.
Rob
