Hi all,
In our embedded project, our application continuously does
random-access to various ASICs. The ASICs are mapped by a BAT
register:
- Forcing the application to use system-calls for accessing the ASICs
would incur a too-big overhead.
- Adding _PAGE_USER to bat-mapping is ok but would export the mapping
to every single userspace processes.
- I'm contemplating adding 2 bitmasks (1 read, 1 write) into the
mm_struct:
- each bit in the mask represent a BAT register that should be
accessible from userspace.
- in switch_mm, prior to the call to set_context(), the BATs's Vp
bits would be updated based on the masks of the `next' mm.
My questions are:
- has it been discussed/comptemplate/done before?
- what issues (performance,style,...) do you think such a change would
create?
- is a BAD idea?
- How the X server access the hw on PPC?
Thanx
--
Linh Dang
--
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