[Intel-gfx] [PATCH v2] drm/i915: Per-DDI I_boost override

[Ville Syrjälä]

On Fri, Jul 03, 2015 at 04:25:15PM +0100, Damien Lespiau wrote:
> On Fri, Jul 03, 2015 at 06:21:58PM +0300, Ville Syrjälä wrote:
> > > In the old VBT spec I have, each child_dev_config is supposed to have
> > > only 33 bytes. But in this patch you're increasing it to 38. I believe
> > > this is what's causing the errors I see when I boot my BDW.
> > > 
> > > Are you sure they increased the VBT's ChildDevInfo to more than 33
> > > bytes? I don't have access to your VBT spec right now, so I can't do a
> > > proper review or a suggestion on how to fix the problem.
> > 
> > The size depends on the version. On BSW last I looked it was maybe 36 or
> > 37 bytes.
> > 
> > I'm not sure we want to change common_child_dev_config since it's meant
> > to be some kind of common stuff. So maybe add another member into the
> > union for this stuff. Of course that still incrases the size of the union
> > so other changes are required to make it work.
> > 
> > Fortunately we copy these things out from the VBT, so I think just
> > making sure the memcpy() doesn't try to copy too much and fixing the size
> > check should be all that's needed. That would leave any extra we didn't
> > fill with the copy zeroed, and if having it zeroed isn't good enough
> > we can of course sprinkle more version checks around.
> > 
> > And I guess we should still check that the size is at least 33 bytes
> > since that was the official size for the longest time.
> 
> So child_dev_size lies to us?

No, it's correct. But we require it to be at least as big as our
union child_device_config, which the patch changes from 33 to 37
bytes.

-- 
Ville Syrjälä
Intel OTC