Re: [Linux-fbdev-devel] Some questions

[Thomas W. <th...@wi...>]

Antonino Daplas wrote:
>>>2. do not refresh unless var changed - fasted but can result in
>>>corruption/crash if registers were changed behind the back of fbdev
>>
>>I think one can rely on tidyness of applications changing the registers. 
>>Like X does.
> 
>  
> Unfortunately, this is what we are trying to prevent.  X assumes that
> the console is in text mode, so only registers that affect text mode are
> restored.  Frequently, cursor registers and bitmaps, as an example, are
> not refreshed.  There's probably more, ie accel engine, etc.

That surprises me. The X drivers I looked at (quite a bunch) restore all 
registers (that need to be restored, that is)

>>>3. selective refresh - do not refresh if switching between "trusted"
>>>consoles, refresh if switching from "untrusted" consoles.
>>
> 
> I actually prefer #3, and I already have working code for this.  We can
> also make this driver switchable (ie, drivers that are not affected by X
> can disable this, and only drivers that are affected such as the riva,
> aty, radeon, etc can turn this on).

What exactly is a "trusted" console?

Thomas


-- 
Thomas Winischhofer
Vienna/Austria
mailto:th...@wi...          *** http://www.winischhofer.net