Messages in this thread | | | From | Ian Collier <> | Subject | vesafb, MMIO & MTRR (Re: Next round of console patches) | Date | Thu, 3 Sep 1998 13:43:25 +0100 (BST) |
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> vesafb will use the whole available video memory (for ypan && scrollback). > If the video memory size reported by the VESA BIOS is not correct => game > over.
Indeed. If the VESA BIOS does not subtract the MMIO area before reporting the framebuffer size then it is IMHO broken.
To go off at a tangent...
In fact, the size reported by VESA has to be a multiple of 64K so it is rounded down. There should be no MMIO area in the framebuffer reported by VESA. Unfortunately, though, if you believe both the framebuffer size and the maximum number of lines as reported by the BIOS then your program might break (example: on Neomagic NM2093 system at 1024 bytes per line the BIOS reports the maximum number of lines as 1117 but the BIOS claims the framebuffer is only 1088K - so you mmap 1088K and try to use 1117K and your program segfaults. I guess there is actually 1152K installed on the board but it uses the rest of the memory for its own purposes).
imc
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