Messages in this thread | | | Date | Wed, 27 Apr 2005 23:50:56 -0700 | From | "David S. Miller" <> | Subject | Re: pci-sysfs resource mmap broken (and PATCH) |
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On Thu, 28 Apr 2005 16:39:13 +1000 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> On Wed, 2005-04-27 at 22:37 -0700, David S. Miller wrote: > > On Wed, 27 Apr 2005 23:33:11 -0600 > > > The 'offset' argument is defined to be page aligned > > when passed to mmap(). > > mmap API in general is defined to only ever deal with page aligned > parameters & return values no ?
Yes.
> Except from that page alignment thing ... which is the root of the > problem.
You can hide all of those problems in libpci.a or whatever. You page align the offset, but pass back to the user a pointer with his sub-page offset applied to it.
The kernel wants pages, so just give it pages :-)
> > I hate to say this, but the largest consumer of this stuff is the > > X server, so we really need to force ourselves to work in parallel > > on clean X server support. > > Cleaning X.org is my goal, this is why I'm trying to clean the kernel > side first :) I'm also working separately on the problem of VGA access > arbitration (We'll probably do a joint session with the desktop summit > an the kernel summit about those issue).
Yeah, that one is all about enabling VGA forwarding in the bridges.
Taking out all of the resource garbage in the X server, and replacing it with properly synchronized calls in the kernel for mapping ROMs and changing the current VGA forwarding seems to be the way to go.
> > On many platforms some kind of "side effect" bit in the PTE > > determine if store buffer compression can happen in the processor. > > We'd want to not set such a bit for things like frame-buffers and > > the like. > > Yes, and I think that pretty much match with PCI devices exposing a > "prefetchable" BAR, don't you agree ?
Some scsi controllers have prefetchable set in their normal register BARs. The sym53c8xx does if I remember correctly.
Anyways, what I'm trying to say is that blinding turning prefetchable BAR into "don't set side effect bit in PTE" might not be so wise.
I really think it's a userlevel decision. That's where all the ioctl() garbage came from for the /proc/bus/pci mmap() stuff. It was for chossing IO vs MEM space, and also for setting these kinds of mapping attributes. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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