[Bug 262638] overly strict check of hpet region size

From: <bugzilla-noreply_at_freebsd.org>
Date: Fri, 18 Mar 2022 16:54:41 UTC

Mark Johnston <markj@FreeBSD.org> changed:

           What    |Removed                     |Added
             Status|New                         |Open
                 CC|                            |markj@FreeBSD.org

--- Comment #3 from Mark Johnston <markj@FreeBSD.org> ---
The value of 1024 comes directly from the Intel specification, see section 2.1:

Some AMD documentation for 16h processors suggests that only three timers are
available, and the MMIO space for HPET registers is indeed only 512 bytes in

Changing the value of HPET_MEM_WIDTH doesn't seem like the right solution:
hpet_identify() uses that constant to initialize the memory resource for the
hpet driver if it can't get the resource size from acpi.  We could instead
modify the check in hpet_attach() to first verify that the resource is large
enough to read the capabilities register, then check it again once we have the
number of timers.

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