Re: Restoring Screen when coming back from KD_GRAPHICS

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> I was using "save" as in "don't overwrite".    The fb_var_screeninfo and 
> fb_cmap structures are the two main ones.  If we have seperate ones for 
> each vt and one for when a graphics app then the contents of each is 
> "saved" and can be restored by fbcon very easily.

Ok.

> But if a fbdev can't recreate it's state from the information that fbcon 
> provides (var, cmap, etc) because it has some internal driver or hw 
> state info then there needs to be a way for fbcon to tell the fbdev "put 
> your internal state in this buffer" so it can be remembered when things 
> get restored later.  That way the fbdev doesn't have to worry about any 
> of the high level stuff.  It just gets the contents of that buffer back 
> when things get restored.   Fbcon can ask the driver on startup as to 
> how many bytes of buffer space does it need for it's save area and if 
> the fbdev doesn't need any (it can totally restore it's state using the 
> normal set_var mechanism) it can just say zero.

I think we don't need (nor want) to go down that path. And I fail to
see what state info would matter anyway.

> >I think we just need to instruct the fbdev to restore it's mode via
> >a set_var with an activate flag FB_ACTIVATE_FORCE, that bypass any
> >test inside the driver about the mode changing from the current info-var,
> >that is basically forcing it to re-apply it's current var. Most drivers
> >will also reset the accel engine properly if any when doing so.
> >  
> >
> 
> Can all the fbdevs restore everything with just that information?   If 
> so then we don't have to worry about the internal state save buffer 
> stuff above.

The fbdev's can restore what they need. What I mean is they can restore the
whole state needed for the mode, the palette and their own accel ops to
behave properly. That's all they have to care about. If a gfx app need
more engine state, it's up to this app to save/restore it.

ben.
 



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