Man, I did not know that my picking on Legacy vBIOS, VBT, and legacy mechanisms will make such a noise. And so many responses.
I should say, I am glad that I provoked such an avalanche of info, since, I have to say, I am learning a lot reading this email thread. I hope others learn a lot too. And... We all are trying to connect missing puzzles. I certainly do (and pass to you what I do know - NOT always the case)! I just came back from BBALL, and I am pretty dead, as dead cat's last jump... It was tough on my body (3:3 on full real court, two hoops, 2 hours)... I'll try reasonably to reply to these emails! :-( > Intel provides a binary-only GOP driver (IntelGopDriver.efi) to OEMs who > embed it into their UEFI implementations. I don't know if it itself requires VBT. Igor, In present BIOSes (most of them are 64b, thus UEFI), as I understand, there are three modes of operations: [1] Legacy only (CSM ON); [2] Combined mode (have no idea how this does work); [3] True UEFI (CSM OFF)! Now, I never use/used mode [2]. I am NOT fan of mixing these modes. I use [1] if I must too, but my preferred mode is [3]. Regarding these two modes,: [1] Legacy - does use vBIOS (maximum size 64KB), INT 10H, VBT, and all this is inherited by OS. [3] UEFI - does use GOP driver (MORE that 64KB in size, there is no such a limit as for vBIOS). These are The Facts. Matt (De Viller) can beat me with the baseball bat, but this I know, this is in concrete. I would NOT change (about what I wrote here above) my opinion. It seems that, after GOP dies, still, orphaned VBT survives post mortem UEFI (as part of UEFI run time data passed to OS). I (here, Matt makes me doubtful, and I will thank him for that) always was naive and thought that VBT is NOT part of GOP driver. But, apparently, I might be mistaken, and Matt (De Viller) is probably right. Now... The bloody name VBT is one which confuses me: Video BIOS Table (VBT). This is my problem, but, if I better think, maybe INTEL CCG/OTC pros wanted just to continue to inherit the transparency. About what I think, about VBT, I'll reply to Matt (DaEmon) and Coreboot himself. ;-) I am glad that I missed some points. :-) Zoran On Wed, Apr 5, 2017 at 7:59 PM, Igor Skochinsky via coreboot < coreboot@coreboot.org> wrote: > Hello Zoran, > > Wednesday, April 5, 2017, 5:03:33 PM, you wrote: > > ZS> To Coreboot, > > ZS> http://www.uefi.org/sites/default/files/resources/ > UPFS11_P4_UEFI_GOP_AMD.pdf > > ZS> Please, read about GOP, and what GOP suppose to be. > > ZS> So, GOP actually need to replace vBIOS, VBT, legacy INT 10H, and > ZS> complete VBE 3.0 standard. Why (I have no idea what INTEL does > ZS> with GOP and how it implements it) it is not done in this > ZS> fashion...?! At least this is my impression how this should be done. > > Well, yes, the GOP is used in UEFI for video output (e.g. in the UEFI > shell or the BIOS setup screens) and in theory any OS can use it to > access video after boot although I don't know any OS that does; at > least both Linux and Windows use their own drivers which talk to the > hardware directly (and those drivers seem to require VBT currently). > Though I think the Windows bootloader (winload.efi) can use GOP to > display the boot menu. > > Intel provides a binary-only GOP driver (IntelGopDriver.efi) to OEMs who > embed it into their UEFI implementations. I don't know if it itself > requires VBT. > > > ZS> I'll continue to investigate. > > ZS> Thank you, > ZS> Zoran > > ZS> On Wed, Apr 5, 2017 at 4:54 PM, Matt DeVillier > ZS> <matt.devill...@gmail.com> wrote: > ZS> On Tue, Apr 4, 2017 at 10:12 PM, Zoran Stojsavljevic > ZS> <zoran.stojsavlje...@gmail.com> wrote: > ZS> Hello Matt, > > ZS> Pretty sure there is NO Option ROM, vBIOS and INT10H. Why INTEL > ZS> for GOP uses VBT is point of debate. Probably just reduced > ZS> functionality up to 1280x1024. So they have VBT to support BIOS phase > GOP GFX. Only! > > ZS> From what I can tell, it's mainly used to provide the output > ZS> connector types/mapping to the GOP driver, as well as level shifting > etc. > ZS> > > ZS> But I am also 100% sure neither GOP, neither VBT survives post > ZS> BIOS phase. It is out of mind to use VBT for WUXGA, or 1080p, or > ZS> 4K displays, don't you agree? The detected GFX I/F are passed to > ZS> Linux as Run Time info (via HOB). Then Linux brings from scratch > ZS> GFX, using its own, modern I/Fs. And ports appropriate drivers to > existing GFX info from HOB. > > ZS> The VBT data is used by both the Linux and Windows display > ZS> drivers (via the OpRegion ACPI structure), and the latter will > ZS> give you a nice black screen if your VBT is missing or incorrectly > ZS> configured. As I noted above, it appears to be used more for > ZS> output/pipe info than display modes (which are all generated from > ZS> EDID, outside of standard VESA/CEA ones) > > ZS> On Tue, Apr 4, 2017 at 10:12 PM, Zoran Stojsavljevic > ZS> <zoran.stojsavlje...@gmail.com> wrote: > ZS> Hello Matt, > > ZS> Pretty sure there is NO Option ROM, vBIOS and INT10H. Why INTEL > ZS> for GOP uses VBT is point of debate. Probably just reduced > ZS> functionality up to 1280x1024. So they have VBT to support BIOS phase > GOP GFX. Only! > > ZS> But I am also 100% sure neither GOP, neither VBT survives post > ZS> BIOS phase. It is out of mind to use VBT for WUXGA, or 1080p, or > ZS> 4K displays, don't you agree? The detected GFX I/F are passed to > ZS> Linux as Run Time info (via HOB). Then Linux brings from scratch > ZS> GFX, using its own, modern I/Fs. And ports appropriate drivers to > existing GFX info from HOB. > > ZS> Zoran > > ZS> On Tue, Apr 4, 2017 at 11:51 PM, Matt DeVillier > ZS> <matt.devill...@gmail.com> wrote: > > > ZS> On Tue, Apr 4, 2017 at 2:23 PM, Zoran Stojsavljevic > ZS> <zoran.stojsavlje...@gmail.com> wrote: > ZS> Furthermore, let me tell you all that this is a mechanism to > ZS> support ONLY The Legacy BIOS (UEFI works ONLY with GOP, but this > ZS> is another dimension/discussion), and, to all of your knowledge > ZS> (which I have no idea how deep it is, I doubt), VBT table survives > ZS> postmortem BIOS. By Linux, it will be RELOCATED into much higher > ZS> (over 1MB) 32bit protected mode memory (addresses recalculated), > ZS> and still use INT10H, using vBIOS (Option ROM, my best guess) down > there. > > > ZS> no, the UEFI GOP driver needs the VBT to actually do anything. > ZS> Look at any current PC UEFI firmware, or even x86 ChromeOS > ZS> firmware, and you'll see they all use/contain a VBT still. > > > > > -- > WBR, > Igor mailto:skochin...@mail.ru > > > -- > coreboot mailing list: coreboot@coreboot.org > https://www.coreboot.org/mailman/listinfo/coreboot >
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