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From: "Hans J. Koch" <>
To: Mike Frysinger <>
Cc: Greg KH <>, "Hans J. Koch" <>,
	Mike Frysinger <>,
Subject: Re: [PATCH] UIO: only call pgprot_noncached if defined
Date: Wed, 5 Nov 2008 19:27:44 +0100	[thread overview]
Message-ID: <20081105182743.GE6382@local> (raw)
In-Reply-To: <>

On Wed, Nov 05, 2008 at 12:33:37PM -0500, Mike Frysinger wrote:
> On Wed, Nov 5, 2008 at 11:33, Greg KH wrote:
> > On Wed, Nov 05, 2008 at 12:36:11PM +0100, Hans J. Koch wrote:
> >> There seem to be archs that cannot easily implement a sensible
> >> pgprot_noncached() function, so we should merge this patch. UIO doesn't
> >> compile on these archs right now.
> >
> > No, we should fix those arches to have that function at least NULLed
> > out.  Isn't there only one, Blackfin?  Putting #ifdefs in .c files is
> > not something we really want to do if at all possible.
> that was my question.  this function isnt documented.  if the hardware
> doesnt support it, is the right thing really for the arch to lie to
> drivers and not actually give back cached settings even though it
> asked for non-cached ?

Well, if there's no possibility to map device memory in a non-cached
way, it's very likely you don't want to use UIO at all. If there's a few
seconds between a write and the value actually appearing in the hardware
register, you will certainly don't see the results you expect.

If Blackfin can't mmap non-cached memory, we should make UIO depend on


  parent reply	other threads:[~2008-11-05 18:28 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-29 17:26 Mike Frysinger
2008-10-29 20:53 ` Hans J. Koch
2008-11-05  0:06   ` Mike Frysinger
2008-11-05 11:36 ` Hans J. Koch
2008-11-05 16:33   ` Greg KH
2008-11-05 17:08     ` Hans J. Koch
2008-11-05 17:43       ` Mike Frysinger
2008-11-05 17:33     ` Mike Frysinger
2008-11-05 17:42       ` Greg KH
2008-11-05 17:55         ` Mike Frysinger
2008-11-05 18:27       ` Hans J. Koch [this message]
2008-11-05 18:36         ` Mike Frysinger

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