Writing a driver: how do I get resources?

John Baldwin jhb at freebsd.org
Tue Sep 23 15:23:50 UTC 2008

On Tuesday 23 September 2008 08:38:25 am Gavin Atkinson wrote:
> Hi all,
> Please forgive me if this email makes very little sense: I've never
> really looked at how ACPI works from a driver's perspective, so don't
> really know if what I'm trying to do is even correct.
> I'm expanding the acpi_sony driver to cover the PNP ID SNY6001.  When I
> simply claim it by returning 0 from the probe, I get the following I/O 
> acpi_sony0: <Sony programmable I/O> port 0-0x1f on acpi0
> However, if I'm reading the AML[1] and Linux drivers[2] correctly, this
> is not the correct range.  It appears that the _PRS method offers a
> choice of four I/O ranges and four IRQs, one of which is then selected
> by evaluating _SRS.  None of them are 0-0x1f.
> Firstly, does that make sense?  Secondly, how do I do this from a
> driver?  I can't see any other drivers that seem to get this involved in
> ACPI, indeed the only mention of evaluating _PRS is within the ACPI code
> itself.
> Lastly, I only have intermittent access to this laptop, so I apologise
> if I can't test things quickly.

Our ACPI driver isn't smart enough yet (AFAIK) to allocate new resources for a 
device that doesn't have any.  That logic should be in acpi_alloc_resource() 
and once that is present then your driver just needs to do the usual 
bus_alloc_resource() stuff to work.

John Baldwin

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