On Wed, Feb 22, 2017 at 10:15:12AM +0200, Jani Nikula wrote: > On Tue, 21 Feb 2017, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Feb 21, 2017 at 06:40:25PM +0200, Jani Nikula wrote: > >> Sometimes it would be most enlightening to debug systems by replacing > >> the VBT to be used. For example, in the referenced bug the BIOS provides > >> different VBT depending on the boot mode (UEFI vs. legacy). It would be > >> interesting to try the failing boot mode with the VBT from the working > >> boot, and see if that makes a difference. > >> > >> Add a module parameter to load the VBT using the firmware loader, not > >> unlike the EDID firmware mechanism. > > > > What's the mechanism by which they would create a valid VBT file? > > Does > > cat /sys/kernel/debug/dri/0/i915_opregion > vbt.fw > > work and provide a starting point for corrections? > > The debugfs file for just the VBT is i915_vbt. > > For starters I only thought of using the VBT from the other boot mode, > and didn't really think of actually modifying the file, let alone making > it easy to modify the file using some tool for example. > > There is a Windows-only BIOS Modification Program, or BMP, to modify the > VBT. It's referenced in a bunch of public documentation, but apparently > the tool itself is not publicly available. And even if it were, it's > neither free nor for Linux. I've never touched it myself. > > Given the fact that we have tools/intel_vbt_decode in IGT, it should not > be hard to write such a tool. The information is all there for an > interested party. Just a SMOP. ;) No worries, all I wanted was a very short step-by-step guide as to how one would experiment with, use, or test this feature. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
