Re: [RFC PATCH 00/17] Drop uses of pci_read_config_*() return value
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2020-08-02 19:14:14
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, linux-wireless, lkml
On Sun, Aug 02, 2020 at 08:46:48PM +0200, Borislav Petkov wrote:
On Sun, Aug 02, 2020 at 07:28:00PM +0200, Saheed Bolarinwa wrote:quoted
Because the value ~0 has a meaning to some drivers and onlyNo, ~0 means that the PCI read failed. For *every* PCI device I know.
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? If there's something about that in the spec I'd love to know where it is because it would simplify a lot of things. I don't think we should merge any of these patches as-is. If we *do* want to go this direction, we at least need some kind of macro or function that tests for ~0 so we have a clue about what's happening and can grep for it. Bjorn