On Tuesday, March 8, 2005 9:58 pm, Jon Smirl wrote: > On Wed, 09 Mar 2005 16:37:13 +1100, Benjamin Herrenschmidt > > <[EMAIL PROTECTED]> wrote: > > On Tue, 2005-03-08 at 23:35 -0500, Jon Smirl wrote: > > > This is from /linux-2.5/Documentation/filesystems/sysfs-pci.txt. It > > > describes how ia64 is achieving legacy IO. The VGA control code > > > probably needs to be coordinated with this. > > > > This is a different thing, and I will implement it on ppc one of these > > days. This is for issuing the IO cycles on the bus. It has nothing > > to do with the actual arbitration work. > > Each one of these legacy spaces corresponds to an allowable > simultaneous VGA use. There should be one arbiter per legacy space.
Jon, I think the arbiters have to be per-resource rather than per-legacy space. AIUI, the arbiters are there to deal with multiple devices on the same bus that respond to the same cycles, like two VGA cards in one legacy I/O domain. You either need to relocate one of them so that they don't have overlapping I/O ranges or disable one while you talk to the other. IOW, legacy space is the whole I/O window of a given bus or PCI domain (granularity defined by the platform--some will only have one I/O space), and the arbiter's job is to arbitrate access to subsets of each window. I think the the VGA stuff here complements the legacy interface rather than conflicting with it. Jesse - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/