Messages in this thread | | | From | Thomas Backlund <> | Subject | Re: [PATCH 2.4.21-rc1] vesafb with large memory | Date | Tue, 6 May 2003 03:21:23 +0300 |
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Viestissä Sunnuntai 4. Toukokuuta 2003 12:49, Willy TARREAU kirjoitti: > Hi Thomas, > > > the correct line should AFAIK be: > > video_size = screen_info.lfb_width * screen_info.lfb_height * > > video_bpp; > > > > (AFAIK we are calculating bits here, not bytes so the '/8' you used is > > wrong... could you try without it, and let me know...) > > No, after verification, I insist, we're really calculating BYTES here. > Please take a look :
Yes, you are right...
[...] > > So I think that the correct line really is : > video_size = screen_info.lfb_width * screen_info.lfb_height * > video_bpp / 8;
There is a problem with this, ... If we calculate the exact memory like this, there wont be any memory remapped to do double/tripple buffering... So the question is: shoud one take the formula and add ' * 2' to atleast get the double buffering supported... (in the patch I made for mdk, I kept a modified override part so that the user can change this, if he needs it....)
Alan, any comments on this?
> (Which also handles line widths which are not multiple of 8).
Well actually, in that formula it does not matter where you put the '/8', the result is always the same...
> BTW, I wonder why we truncate the mtrr size to the highest lower power > of 2. Shouldn't we round it up to the next one ? >
Isn't it a hardware requirement? I think I read it in a nvidia document once... (of course they may be wrong...)
-- Thomas Backlund
tmb@iki.fi www.iki.fi/tmb
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