Hi David,
On Sat, 3 Mar 2007 08:47:21 -0700, David Hubbard wrote:
I've been thinking about it too, but I could convince myself quickly
that it would never work, so I didn't bother posting about it ;)
As you found out yourself, it isn't trivial to allocate the ports
dynamically. Either you'll end up with lots of 1-address ranges, or
you'll allocate more than is actually needed, or you'll need a
buddy-allocator like mechanism to merge contiguous ranges. This sounds
quite complex to get right. And very costly, too. I don't know the
exact algorithm to find out whether an I/O range is already allocated
or not, and by who, but having to do it for each port access from AML,
forever, sounds like a huge overhead.
On top of that, there is a risk that another driver already requested
the I/O range. And we do not want to prevent ACPI from accessing it!
OK, it would be cleaner that the current situation in a way, but it
could also have bad consequences as was underlined elsewhere in this
thread.
What we want is to grant access to the resources to at least ACPI (and
ACPI only if we can't do better), or if possible to both ACPI and
individual drivers but with some mechanism avoiding concurrent access
(be it a mutex or a port forwarder.)
--
Jean Delvare
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