[linuxsh-shmedia-dev] Mapping a PCI address into user space

[Gaster, B. <ben...@su...>]

Hello!
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I have modified the bitkeeper Kyro framebuffer driver to provide
additional ioctl calls for the creation of overlay surfaces (to handle
YUV to RGB colour conversion). Currently two calls are required for
creation of an overlay surface and a creation of viewport (a scaling
window mapping the overlay surface on to the RGB output) which returns a
pointer to the viewport surface. Currently the pointer returned can only
be written to in Kernel space which I assume is due to the pointer into
the PCI address space is mapped only in kernel space and not in user
space. I presume that it is possible to map the pages to be written by a
particular user process but I not sure how to do this and weather it is
the best approach.=20
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I suppose it would be possible to extend the framebuffer driver to
provide an additional driver interface for overlay surfaces and thus use
mmap to create a memory mapped region but this seems like over kill for
the functionally that I'm after.
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What do other people think?
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ben.