On Tue, Apr 4, 2017 at 10:12 PM, Zoran Stojsavljevic < zoran.stojsavlje...@gmail.com> wrote:
> Hello Matt, > > Pretty sure there is NO Option ROM, vBIOS and INT10H. Why INTEL for GOP > uses VBT is point of debate. Probably just reduced functionality up to > 1280x1024. So they have VBT to support BIOS phase GOP GFX. Only! > >From what I can tell, it's mainly used to provide the output connector types/mapping to the GOP driver, as well as level shifting etc. > > But I am also 100% sure neither GOP, neither VBT survives post BIOS phase. > It is out of mind to use VBT for WUXGA, or 1080p, or 4K displays, don't you > agree? The detected GFX I/F are passed to Linux as Run Time info (via HOB). > Then Linux brings from scratch GFX, using its own, modern I/Fs. And ports > appropriate drivers to existing GFX info from HOB. > The VBT data is used by both the Linux and Windows display drivers (via the OpRegion ACPI structure), and the latter will give you a nice black screen if your VBT is missing or incorrectly configured. As I noted above, it appears to be used more for output/pipe info than display modes (which are all generated from EDID, outside of standard VESA/CEA ones) On Tue, Apr 4, 2017 at 10:12 PM, Zoran Stojsavljevic < zoran.stojsavlje...@gmail.com> wrote: > Hello Matt, > > Pretty sure there is NO Option ROM, vBIOS and INT10H. Why INTEL for GOP > uses VBT is point of debate. Probably just reduced functionality up to > 1280x1024. So they have VBT to support BIOS phase GOP GFX. Only! > > But I am also 100% sure neither GOP, neither VBT survives post BIOS phase. > It is out of mind to use VBT for WUXGA, or 1080p, or 4K displays, don't you > agree? The detected GFX I/F are passed to Linux as Run Time info (via HOB). > Then Linux brings from scratch GFX, using its own, modern I/Fs. And ports > appropriate drivers to existing GFX info from HOB. > > Zoran > > On Tue, Apr 4, 2017 at 11:51 PM, Matt DeVillier <matt.devill...@gmail.com> > wrote: > >> >> >> On Tue, Apr 4, 2017 at 2:23 PM, Zoran Stojsavljevic < >> zoran.stojsavlje...@gmail.com> wrote: >> >>> Furthermore, let me tell you all that this is a mechanism to support >>> ONLY The Legacy BIOS (UEFI works ONLY with GOP, but this is another >>> dimension/discussion), and, to all of your knowledge (which I have no idea >>> how deep it is, I doubt), VBT table survives postmortem BIOS. By Linux, it >>> will be RELOCATED into much higher (over 1MB) 32bit protected mode memory >>> (addresses recalculated), and still use INT10H, using vBIOS (Option ROM, my >>> best guess) down there. >>> >>> >> no, the UEFI GOP driver needs the VBT to actually do anything. Look at >> any current PC UEFI firmware, or even x86 ChromeOS firmware, and you'll see >> they all use/contain a VBT still. >> > >
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