Re: Re: [patch 1/1] intelfb-voffset

[Sylvain Meyer <sylvain.meyer@worldonline.fr>]

Andrew Morton a écrit:

>sylvain.meyer@worldonline.fr wrote:
>  
>
>>- Add voffset option to avoid conficts with Xorg i810 driver
>>    
>>
>
>Please provide more info.
>
>- How does it "avoid conflicts"?
>
    It avoids conflicts in using memory allocations for framebuffer, hw 
cursor and ring buffer which cannot be corrupted by the X driver. The 
problem seems to be the exclusive use of BIOS calls in the X driver 
instead of direct access to the hardware as in the intelfb driver. I 
don't know what the BIOS do but i can see the corruption. In the X 
driver, the BIOS is called to increase the stolen memory (part of the 
aperture memory already allocated by the BIOS) if it is too small. I 
think it's part of the problem.

>
>- How is the user to know that he needs to provide this module parameter?
>
    The default parameter should be ok with default configuration of the 
X driver. If VideoRam parameter is increased in xorg.conf, maybe a 
different voffset should be passed to the linux kernel (now VideoRam 
defaults to 32MB, voffset to 48 MB).
    Anyway, if i have spare time this week-end, i'll come with a small 
doc. Just to to know, i borrowed this idea to the i810 driver, so the 
parameter is already in use today.

>
>- Is it not possible to prevent these "conflicts" without the use of a
>  module parameter?
>
    If i had the datasheet of the chips, maybe but now without lobbying 
Intel and working blind, my answer is no. Sorry.

>IOW: it's really a cop-out to require that the user know about some obscure
>module parameter to be able to amke their system work correctly.  We
>really, really want these things to "just work".
>  
>
    Yes, I share your concern but now I don't know how to do it.

Sylvain






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