Em Tue, 28 Dec 2021 16:06:44 +0100 Niklas Schnelle <schnelle@xxxxxxxxxxxxx> escreveu: (on a side note: the c/c list of this patch is too long. I would try to avoid using a too long list, as otherwise this e-mail may end being rejected by mail servers) > On Tue, 2021-12-28 at 13:54 +0100, Mauro Carvalho Chehab wrote: > > > ---8<--- > > > > > > > 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. > > > > I didn't look at the other patches on this series, but why it is needed > > to deal with them on a separate way? Won't "PCI" and "HAS_IOPORT" be enough? > > > > I mean, are there any architecture where HAVE_PCI=y and HAS_IOPORT=y > > where LEGACY_PCI shall be "n"? > > In the current patch set LEGACY_PCI is not currently selected by > architectures, though of course it could be if we know that an > architecture requires it. We should probably also set it in any > defconfig that has devices depending on it so as not to break these. > > Other than that it would be set during kernel configuration if one > wants/needs support for legacy PCI devices. For testing I ran with > HAVE_PCI=y, HAS_IOPORT=y and LEGACY_PCI=n on both my local Ryzen 3990X > based workstation and Raspberry Pi 4 (DT). I guess at the moment it > would make most sense for special configs such as those tailored for > vitualization guets but in the end that would be something for > distributions to decide. IMO, it makes sense to have a "default y" there, as on systems that support I/O space, disabling it will just randomly disable some drivers that could be required by some hardware. I won't doubt that some of those could be ported from using inb/outb to use, instead, readb/writeb. > > Arnd described the options here: > https://lore.kernel.org/lkml/CAK8P3a3HHeP+Gw_k2P7Qtig0OmErf0HN30G22+qHic_uZTh11Q@xxxxxxxxxxxxxx/ Based on Arnd's description, LEGACY_PCI should depend on HAS_IOPORT. This is missing on patch 1. You should probably reorder your patch series to first create HAS_IOPORT and then add LEGACY_PCI with depends on, as otherwise it may cause randconfig build issues at robots and/or git bisect. I would also suggest to first introduce such change and then send a per-subsystem LEGACY_PCI patch, as it would be a lot easier for maintainers to review. > > > > > > 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." > > > > I would still avoid calling it LEGACY_PCI, as this sounds too generic. > > > > I didn't read the PCI/PCIe specs, but I suspect that are a lot more > > features that were/will be deprecated on PCI specs as time goes by. > > > > So, I would, instead, use something like PCI_LEGACY_IO_SPACE or > > HAVE_PCI_LEGACY_IO_SPACE, in order to let it clear what "legacy" > > means. > > Hmm, I'd like to hear Bjorn's opinion on this. Personally I feel like > LEGACY_PCI is pretty clear since most devices are either pre-PCIe > devices or a compatibility feature allowing drivers for a pre-PCIe > device to work with a PCIe device. That's the main point: it is *not* disabling pre-PCIe devices or even legacy PCI drivers. It just disables a random set of drivers just because they use inb/outb instead of readb/writeb. It keeps several pure PCI drivers selected, and disables some PCIe for no real reason. Just to give one example, this symbol: > diff --git a/drivers/media/cec/platform/Kconfig b/drivers/media/cec/platform/Kconfig > index b672d3142eb7..5e92ece5b104 100644 > --- a/drivers/media/cec/platform/Kconfig > +++ b/drivers/media/cec/platform/Kconfig > @@ -100,7 +100,7 @@ config CEC_TEGRA > config CEC_SECO > tristate "SECO Boards HDMI CEC driver" > depends on (X86 || IA64) || COMPILE_TEST > - depends on PCI && DMI > + depends on LEGACY_PCI && DMI > select CEC_CORE > select CEC_NOTIFIER > help Disables HDMI CEC support on some Intel motherboards. Any distro meant to run on generic hardware should keep it selected. I can see some value of a "PCI_LEGACY" option to disable all non-PCIe drivers, but this is not the case here. Thanks, Mauro
