Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value
From: Borislav Petkov <bp@alien8.de>
Date: 2020-08-02 20:18:47
Also in:
dmaengine, dri-devel, intel-gfx, linux-crypto, linux-edac, linux-fpga, linux-gpio, linux-hwmon, linux-i2c, linux-ide, linux-iommu, linux-kernel-mentees, linux-pci, linux-rdma, lkml, netdev
On Sun, Aug 02, 2020 at 02:14:06PM -0500, Bjorn Helgaas wrote:
Wait, I'm not convinced yet. I know that if a PCI read fails, you normally get ~0 data because the host bridge fabricates it to complete the CPU load. But what guarantees that a PCI config register cannot contain ~0?
Well, I don't think you can differentiate that case, right?
I guess this is where the driver knowledge comes into play: if the read
returns ~0, the pci_read_config* should probably return in that case
something like:
PCIBIOS_READ_MAYBE_FAILED
to denote it is all 1s and then the caller should be able to determine,
based on any of domain:bus:slot.func and whatever else the driver knows
about its hardware, whether the 1s are a valid value or an error.
Hopefully.
Or something better of which I cannot think of right now...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette