Zack Smith wrote:

Hi all,

As an experiment I tried accessing a part of (shared) video memory
on my system that is not being used for display data, and this caused the
kernel to crash. I have 6 megs of space and the display is using only half,
but accessing above the 3 meg mark causes the problem. Accessing
the lower 3 megs works fine.

Does anyone know what might cause this?

Depends on the driver.  It's possible that the driver did not ioremap
the entire graphics aperture (ie ioremapped only the first 3 megs).  Or
the driver set info->fix.smem_len to only 3 MB instead of 6.

Some drivers are now differentiating between remapped size vs actual
physical size (radeonfb).  info->screen_size, if not zero, tells the
amount of the remapped size while info->fix.smem_len, the actual physical
size.

Tony


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