loading i915 with two graphics cards

[karu.pruun]

Thanks for all the information and links. I had a look at the linux driver
apple-gmux.c, and tried to write a simple DragonFly kernel module that
switches off the gmux. However, I'm stuck with the attachment of the gmux
device: probing via acpi works fine, but I'm not able to allocate IO ports.
The gmux controller is at the LPC bus:

---
LPC
---
pciconf -lv:

isab0 at pci0:0:31:0: . . .
 vendor = 'Intel Corporation'
 device = 'HM55 Chipset LPC Interface Controller'
 class  = bridge
 subclass = PCI-ISA
---

----
GMUX
----
devinfo -rv | grep GMUX:

unknown pnpinfo _HID=APP000B _UID=0 at handle=\_SB_.PCI0.LPCB.GMUX
---

It seems devices attached to LPC bus can be treated as isa devices:

https://lists.freebsd.org/pipermail/freebsd-hackers/2004-October/008733.html

I tried to follow the logic of similar drivers, e.g. acpi_ec, which seems
to sit at the same bus (if I understand it correctly that the handle says
it's located at the LPC bus?):

acpi_ec0 pnpinfo . . . handle=\_SB_.PCI0.LPCB.EC__

The acpi_ec probe part is done with roughly:

---
sys/dev/acpica/acpi_ec.c:
---

acpi_ec_probe(. . .)
{
    . . .

    ACPI_ID_PROBE(device_get_parent(dev), dev, ec_ids)

    . . .
}
---

and that works fine for gmux too. Then attach() calls bus_alloc_resource():

---
sys/dev/acpica/acpi_ec.c:
---

acpi_ec_attach(. . .)
{

    . . .

    res = bus_alloc_resource_any(sc->ec_dev, SYS_RES_IOPORT,
&sc->ec_data_rid, RF_ACTIVE);

    . . .
}
---

But that same call returns a NULL pointer for gmux. Where have I gone
wrong?


Cheers

Peeter

--



On Thu, Aug 4, 2016 at 5:28 PM, Pedro Andrés Aranda Gutiérrez <
paaguti at gmail.com> wrote:

> BTW, there was some code around in the switcher and in mackintosh lists on
> this. File was something like gmux.c
>
>
>
> On 28 Jul 2016, at 11:45, Francois Tigeot <ftigeot at wolfpond.org> wrote:
>
> > On Thu, Jul 28, 2016 at 10:49:26AM +0200, Pedro Andres Aranda Gutierrez
> wrote:
> >> Similar problem here with an ASUS with nVidia Optimus... So it's not Mac
> >> specific...
> >
> > Well, in a way it is.
> >
> > If I'm not mistaken, most Optimus devices have their video outputs
> directly
> > connected to the Intel GPU so it's just a matter of disabling the NVidia
> one.
> >
> > On at least some Macbook models, the video output are connected to a
> third
> > chip, and this chip must also be told to talk exclusively to the Intel
> GPU at
> > boot time first.
> >
> > --
> > Francois Tigeot
>
>
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