Messages in this thread | | | Subject | Re: [PATCH] Define wc_wmb, a write barrier for PCI write combining | From | Bryan O'Sullivan <> | Date | Tue, 28 Feb 2006 09:52:06 -0800 |
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On Tue, 2006-02-28 at 09:44 -0800, Jesse Barnes wrote:
> Something like this would be really handy. Check out fbmem.c:fb_mmap for > a bad example of what can happen w/o it.
:-)
> In fact, I think it might make sense to export WC functionality via an > mmap flag (on an advisory basis since the platform may not support it or > there may be aliasing issues that prevent it); having an arch > independent routine to request it would make that addition easy to do in > generic code.
Yes.
> (In particular I wanted this for the sysfs PCI interface. > Userspace apps can map PCI resources there and it would be nice if they > could map them with WC semantics if requested.)
They already sort of can. It just happens that most arches ignore the WC parameters.
> I don't think it addresses the flushing issue you seem to be concerned > about though.
Yes, I think I could have made my original wording a bit clearer. I don't care if writes have hit the device, merely that they do so in an order that I control.
<b
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