[coyotos-dev] coyotos.ioperm

[Valerio Bellizzomi]

On 06/04/2007, at 11.31, Jonathan S. Shapiro wrote:

>The ioperm capability is removed as of specification v0.6.
>
>Ioperm wasn't a good idea. We may need to re-introduce it, but here are
>the issues:
>
>On most architectures, I/O is memory mapped. For these architectures
>what we need is either
>
>  a) an IOpage abstraction, or
>  b) a physical memory page abstraction with the ability to make that
>     page non-cacheable.
>
>I have not yet decided which way to go on this. We have enough bits in
>memory capabilities to do either solution.
>
>x86 is unique in having an I/O port space. This isn't really a proper
>address space at all, because it isn't mappable. On this architecture we
>have three choices:
>
>  1. Make I/O rights be all or nothing. This is what the EROS IOperm
>     capability did, and what the Coyotos IOperm capability was intended
>     to do.
>
>  2. Come up with a way to memory map the IO bitmap. This is the
>     solution that I prefer, but there are complications.

Did you forget the third choice ?

>
>We need to look at this very soon. I'm hoping to come up with a solution
>where:
>
>  1. Application specifies base virtual address of its IO bitmap (if
>     any).
>  2. Pages mapped at that address must be IO pages, which hold the
>     bitmaps.
>
>Not sure where this is going to end up at this point, but it's a
>relatively small issue.
>
>Since we're about to start fairly intensive work on the kernel I suspect
>this will get resolved pretty soon.
>
>
>BTW: Thanks for asking this, because talking about the cachability hints
>reminded me of something else I forgot to do in the spec.

The main reason I asked is that we need a way to control the state of
individual pins of the parallel port. We are currently doing this with
fedora, but we would like to use coyotos.



>
>
>shap
>
>On Thu, 2007-04-05 at 22:27 +0200, Valerio Bellizzomi wrote:
>> I lost its traces in the March 30 spec update.
>> 
>> Where is it gone ?
>> 
>> 
>> val
>> 
>> 
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