Re: [PATCH 2/2] ACPI Check for backlight support via ACPI video.ko otherwise use vendor ACPI drivers

Matthew Garrett
2008-07-10T10:07:35Z

On Wed, Jul 09, 2008 at 06:00:23PM +0200, Thomas Renninger wrote:
> ...
> > For this to work, the ACPI video driver needs to work as it currently
> > does. It is not correct for it to disable itself on IGD systems.
> Right, now I got it. It is only the T61/Lenovo you must have the opregion
> driver ready or you better fallback to thinkpad_acpi...
> Is that correct?
> I will add a dmi check for Lenovo in video_detect.c.
> That would be:
> - If ACPI Appendix B video brightness functions are found
> | -> use video.ko
> | |
> | -> If it's a ThinkPad, check for Opregion BIOS support
> | -> Use video.ko if IGD parts are implemented (and the one
> | | ThinkPad specific func you had the 750ms delay is available)
> | -> otherwise go back to thinkpad_acpi

This is unnecessary logic. Let's just follow the spec. There's no need
to use thinkpad_acpi here.

> Please also provide an OSI string with your video opregion code parts, so that
> BIOS can check whether the kernel is capable of serving IGD devices. Just
> choose a random string you like, e.g. let OSI("Opregion Video Support")
> return true.

No. The DRM can be (and usually is) built as a module and OSI strings
are going to be checked at ACPI init time. This can't be made to work
correctly. Vendors can choose whether to use the opregion or old-style
support based on whether the driver has enabled the support.