Messages in this thread | | | From | Jesse Barnes <> | Subject | Re: [PATCH] add legacy I/O and memory access routines to /proc/bus/pci API | Date | Wed, 15 Dec 2004 09:00:18 -0800 |
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On Wednesday, December 15, 2004 12:57 am, Benjamin Herrenschmidt wrote: > > I think by "legacy I/O space", you mean specifically "legacy > > I/O *port* space", right? Maybe there's no current use for it, > > but I can imagine supporting MMIO accesses this way, too. > > Legacy IO ports, there should be one space per PCI domain. There is also > legacy ISA memory space though on some ppc's, this doesn't exist at all. > I suspect we want to expose both in a way.
This interface exports both.
> > On i386, anyway ;-) But on ia64, we support multiple 64k I/O port > > spaces (one of them being the 0-64K space that corresponds to the > > i386 "legacy" space). Shouldn't we be able to access them with this > > interface, too? > > We should imho. On ppc, we have a 64k space per domain. One of the main > set of HW that has use for these are VGA cards. It's perfectly possible > to have a Mac with an AGP card in the AGP port and a PCI video card in > one of hte PCI slots, and those are on 2 different domains with > different legacy (0...64k) IO spaces. > > We defininitely want whatever interface we define to deal with that.
Good, because that's exactly what it does. The arch is responsible for returning the legacy I/O port or legacy ISA memory base address given a pci_dev, which is used as a base for the page offset passed into mmap. So e.g. mmap(..., 0xa0000) after doing ioctl(fd, PCIIOC_MMAP_IS_LEGACY_MEM, ...) would get you the VGA framebuffer for the device corresponding to 'fd'.
> There is some work done by Jon Smirl in this area (a VGA access > arbitration driver).
I think Dave Airlie did a version of the vga class driver, and the backend used for /proc/bus/pci could be used for both drivers. I'm using /proc/bus/pci because it's available now and nearly good enough (i.e. this patch was all I needed to get going).
Anyway, I'll post another version with Bjorn's suggestion about the ioctl for choosing config or legacy I/O port read/writes, since it looks like the rest of your concerns are dealt with.
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