Re: [ACPI] Re: Legacy IO spaces (was Re: [RFC] Reliable video POSTing on resume)

Jon Smirl
2005-02-06T00:18:43Z

On Sun, 06 Feb 2005 09:42:32 +1100, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> I think it could be as simple as an additional sysfs entry
> "legacy_enabled" added to all "VGA" devices in the system at the PCI
> layer level. Toggling it triggers the "untoggling" of all others,
> including VGA forwarding on bridges, and enables the path to that
> device. For in-kernel users, a pci_* API would work.
>
> The problem I see though is that it should all be synchronous &
> spinlocked since the vgacon could want to grab at interrupt time (unless
> it's locked by userland, in which case, vgacon should cache & trigger an
> update later).

This is my current code it adds a vga entry to all VGA devices in the system.
http://kerneltrap.org/mailarchive/1/message/15974/flat

Instead of toggle there are four states:
1) off
2) on - make sure everything else is off
3) turn off all VGA devices and remember the active one
4) restore the active one

States 3 and 4 and used for running the reset program. Set state 3 to
remember the active device and turn it off, reset the card which will
enable it's VGA, disable it, set state 4 to restore the saved device.

This thread is active too:
Reliable video POSTing on resume

Restart video after resume is the same problem as posting it in the first place.

--
Jon Smirl
jonsmirl@gmail.com