To: linux-kernel@vger.kernel.org
From: "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RFC] RNG rewrite...
Date: Mon, 17 Oct 2005 16:15:49 -0700 (PDT)
Organization: Mostly alphabetical, except Q, with we do not fancy
Message-ID: <dj1bb5$riu$1@terminus.zytor.com>
References: <20051015043120.GA5946@plexity.net> <4350DCB1.7010201@pobox.com> <20051016005341.GB5946@plexity.net>
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Followup to:  <20051016005341.GB5946@plexity.net>
By author:    Deepak Saxena <dsaxena@plexity.net>
In newsgroup: linux.dev.kernel
> 
> It's a magic regsiter we just read/write and could be done in userspace.
> I also took a look at MPC85xx and it has the same sort of interface but
> also has an error interrupt capability. On second thought a class
> interface is overkill b/c there will only be one RNG per system, so
> I can just do something like watchdogs where we have a bunch of simple
> drivers exposing the same interface. We could do it in user space but
> then we have separate RNG implementations for  x86 and !x86 and I'd
> rather not see that. Can we move the x86 code out to userspace and
> just let the daemon eat the numbers directly from HW? We can mmap() 
> PCI devices, but I don't know enough about x86 to say whether msr 
> instructions can execute out of userspace (or if we want them to...).
> 

MSR instructions cannot execute out of userspace, but the MSR driver
might be possible to use.  It's usually quite slow, however.

	-hpa
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