On Tue, 2021-12-28 at 10:15 +0100, Mauro Carvalho Chehab wrote: > Em Tue, 28 Dec 2021 09:21:23 +0100 > Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> escreveu: > > > On Mon, Dec 27, 2021 at 05:42:46PM +0100, Niklas Schnelle wrote: > > > --- a/drivers/pci/Kconfig > > > +++ b/drivers/pci/Kconfig > > > @@ -23,6 +23,17 @@ menuconfig PCI > > > > > > if PCI > > > > > > +config LEGACY_PCI > > > + bool "Enable support for legacy PCI devices" > > > + depends on HAVE_PCI > > > + help > > > + This option enables support for legacy PCI devices. This includes > > > + PCI devices attached directly or via a bridge on a PCI Express bus. > > > + It also includes compatibility features on PCI Express devices which > > > + make use of legacy I/O spaces. > > This Kconfig doesn't seem what it is needed there, as this should be an > arch-dependent feature, and not something that the poor user should be > aware if a given architecture supports it or not. Also, the above will keep > causing warnings or errors with randconfigs. > > Also, the "depends on HAVE_CPI" is bogus, as PCI already depends on > HAVE_PCI: Ah yes you're right. > > menuconfig PCI > bool "PCI support" > depends on HAVE_PCI > help > This option enables support for the PCI local bus, including > support for PCI-X and the foundations for PCI Express support. > Say 'Y' here unless you know what you are doing. > > So, instead, I would expect that a new HAVE_xxx option would be > added at arch/*/Kconfig, like: > > config X86 > ... > select HAVE_PCI_DIRECT_IO > > It would also make sense to document it at Documentation/features/. I'll look into that, thanks. > > > All you really care about is the "legacy" I/O spaces here, this isn't > > tied to PCI specifically at all, right? > > > > So why not just have a OLD_STYLE_IO config option or something like > > that, to show that it's the i/o functions we care about here, not PCI at > > all? > > > > And maybe not call it "old" or "legacy" as time constantly goes forward, > > just describe it as it is, "DIRECT_IO"? > > Agreed. HAVE_PCI_DIRECT_IO (or something similar) seems a more appropriate > name for it. > > Thanks, > Mauro Hmm, I might be missing something here but that sounds a lot like the HAS_IOPORT option added in patch 02. We add both LEGACY_PCI and HAS_IOPORT to differentiate between two cases. HAS_IOPORT is for PC-style devices that are not on a PCI card while LEGACY_PCI is for PCI drivers that require port I/O. This includes pre-PCIe devices as well as PCIe devices which require features like I/O spaces. The "legacy" naming is comes from the PCIe spec which in section 2.1.1.2 says "PCI Express supports I/O Space for compatibility with legacy devices which require their use. Future revisions of this specification may deprecate the use of I/O Space." These two separate config options allow us to compile without support for these legacy PCI devices even on a system where inb()/outb() and friends are required for some PC style devices and for example ACPI.
