Re: LANANA: To Pending Device Number Registrants

[Ingo Oeser]

On Tue, May 15, 2001 at 10:44:23AM -0700, James Simmons wrote:
> different. I do plan on some day merging drm and fbdev into one interface. So
> I plan to change this behavior. I like to see this interface ioctl-less
> (is their such a word ???). You mmap to alter buffers. Mmap is much more
> flexiable than write for graphics buffers anyways. You use write to pass
> "data" to the driver.

The only problem with mmap(): You cannot know, if the page
changed under you a**.

What would first mmap()ed page of the screen look like, if some
accelerator wrote a line there? Invalidating all mmap()ed pages
for each and every accelerator command would be evil. Forbidding
reads of that page is evil, too.

I have the same problem with DSPs, which like to mmap() some of
their memory into the application, but can alter this memory
every instruction the execute.

mmap() has it's beauties, but ...

Regards

Ingo Oeser
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