Paul Mackerras wrote:
Do either of you (or does anyone) have a good mental grasp of how
map handles and offsets are used and manipulated in the X server and
in DRI clients? In particular, I'm interested to know under what
circumstances map handles are generated by arithmetic on other map
handles, or obtained from a source other than a DRM_IOCTL_ADD_MAP
ioctl. Similarly for the offset in a mmap on /dev/dri/cardN; do we do
arithmetic to get those values?
The underlying question is to what extent the handle returned by
DRM_IOCTL_ADD_MAP needs to be predictable (or have a predictable
relationship to other handles) rather than just being an arbitrary
token invented by the kernel DRM code.
In general I'd prefer that the values passed to clients (and back again)
to be abstract tokens rather than actual addresses or offsets into some
unspecified address space.
Which should mean that 32 bits is more than ample to contain them...
Keith
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