[Openchrome-users] modesetting for VN896

[Abraham Varricatt]

Abraham Varricatt wrote:
> Does the current openchrome driver support modesetting on the VN896 ?
>
> The fact that I'm able to boot up Ubuntu on my screen's native 
> resolution makes me think so, but I can't find any confirmation of it on 
> reading the source code.
>
> This is what I use,
>
> svn checkout http://svn.openchrome.org/svn/trunk openchrome
>
> Perhaps I'm thinking in the wrong direction, but I've been studying 
> openchrome source along with DRM source. Now in DRM code, there is a 
> setting that let's you enable modesetting for a graphics chipset.
>
> Does a similar setting exist for openchrome?
>
> Abru
>
>   
Ok, I've been doing some investigating and this is what I've come up 
with. Please correct me if my assumptions are wrong.

By modesetting, obviously the idea is to be able to change the mode on 
your display. Now, from experimentation, I've learned that there is more 
to this than just changing timing information. Suppose that your native 
resolution is 1280x1024. And our driver manages to get the display setup 
right. Now, if we change the resolution to something smaller like, 
640x480 (with timing information), we might end up with just a portion 
of the screen being displayed. (personal experimentation). I can't count 
the pixels, but it seems to fit a box of 640x480, with the rest of my 
screen being black.

I'm guessing that the purpose of modesetting is to get the 640x480 over 
your entire screen and not just a small portion of it.

To achieve this effect, in the openchrome driver, there is a function 
responsible for scaling. ( I don't remember the proper name now) But, 
what this function does is take the ratio of your new mode (640x480, in 
my case) to that of your native resolution (1280x1024) and it just 
continues to display the 1280x1024 mode, but draws a bigger pixel 
depending on the ratio calculated.

 From that info, I'm guessing native mode-setting is NOT avaliable for 
openchrome. Or at least for the VN896.

Am I correct with this?

Yours,
Abru