Reading acpi memory from a driver attached to hostb

[John Baldwin]

On Saturday 18 July 2009 9:39:38 am Andre Albsmeier wrote:
> On Sat, 18-Jul-2009 at 10:25:06 +0100, Rui Paulo wrote:
> > On 18 Jul 2009, at 09:10, Andre Albsmeier wrote:
> > 
> > > On Fri, 17-Jul-2009 at 12:53:53 -0700, Julian Elischer wrote:
> > >> Andre Albsmeier wrote:
> > >>> [CC'ing this to Rui Paulo since he tried to help me a while ago]
> > >>>
> > >>> Since my driver is a child of hostb0, I have no idea of how to  
> > >>> access
> > >>> acpi0's memory area. Here is a devinfo -r to make things clear:
> > >>>
> > >> ...
> > >>>
> > >>> Earlier, I was given the hint to attach as a child of acpi (see the
> > >>> old mail attached below) but in this case I didn't have access to  
> > >>> the
> > >>> hostb registers which I need as well.
> > >>>
> > >>> The only thing I see is: Attach two drivers -- one as child of acpi
> > >>> and another as child of hostb and let them communicate somehow (no
> > >>> idea how to do this).
> > >>>
> > >>> I have also done crazy things like searching for acpi0 and trying
> > >>> to bus_alloc_resource() the memory I am interested in but this also
> > >>> failed.
> > >>>
> > >>> Or is it possible to free(!) somehow the address space from acpi0
> > >>> and pass it to hostb0 so I can bus_alloc_resource() it?
> > >>>
> > >>
> > >> You can probably make two drivers in one which cooperate to
> > >> allow access to both sets of resources.
> > >
> > > Hmm, that's what I meant by: Attach two drivers -- one as child of  
> > > acpi
> > > and another as child of hostb...
> > >
> > > And that's similar to Rui Paulo's suggestion a while ago:
> > >
> > >> You'll probably need to create a fake ACPI child driver to access it.
> > >>
> > >> Create your identify routine with something like:
> > >>
> > >> static void mydriver_identify(driver_t *driver, device_t parent)
> > >> {
> > >>        if (device_find_child(parent, "mydriver", -1) == NULL &&
> > >>            mydriver_match(parent))
> > >>                device_add_child(parent, "mydriver", -1);
> > >> }
> > >>
> > >> mydriver_match() should check if you were given the acpi0 device.
> > >
> > > But in order to attach to acpi0, I need to say
> > >
> > > DRIVER_MODULE( eccmon, acpi, eccmon_driver, eccmon_devclass,  NULL,  
> > > NULL );
> > >
> > > instead of
> > >
> > > DRIVER_MODULE( eccmon, hostb, eccmon_driver, eccmon_devclass,  NULL,  
> > > NULL );
> > >
> > > This way I could attach to acpi but not to hostb anymore....
> > >
> > > I have searched the net for solutions, I have read newbus-draft.txt
> > > and newbus-intro.txt and Warner Losh's newbus-led.c (thanks to all
> > > of these my driver is working on other mainboards where it doesn't
> > > have to access foreign memory) but didn't find anything.
> > 
> > I'm out of ideas.
> > John, do you know if this is a newbus limitation or if it can be  
> > worked around ?
> 
> I assume it is possible somehow, I am just too stupid (it is the first
> driver I wrote). John, for easy reference, here is my initial message:
> 
> http://lists.freebsd.org/pipermail/freebsd-hackers/2009-July/029127.html
> 
> Please remember all, that I need the access to the acpi0 memory location
> only for a few reads during probing/attaching, not later.
> 
> I have also read somewhere that, when resources are allocated, the
> system "walks up" the device tree until it finds the resource. Since
> my driver is below hostb0 and hostb0 is below acpi0 I thought it
> should work but it doesn't..

I think you want to probably patch hostb0 to let bus_set_resource() work and 
then use that.  You could also just explicitly by-pass hostb0 and allocate a 
resource from its parent as a quick hack.  The PCI bus should pass the requst 
up to acpi0.  That is, do:

	BUS_ALLOC_RESOURCE(device_get_parent(device_get_parent(dev)), dev, ...);

instead of

	bus_alloc_resource(dev, ...);

-- 
John Baldwin