Thats the first mistake
> back the address given to the peripheral device earlier. The ISR
> now needs to access the data at the memory location read back, but
It can't
> knows the process ID of the applicaiton in question, but since it
> is not executing with the context of that application, how can it
> convert the address in the applications address space, to its
> own virtual address space?
The page might even be on disk.
The sound drivers may be the most instructive example here. They
DMA to/from buffers and a program can handle them but what is done is
kernel allocates buffers
marks the pages reserved
process does mmap
pages are mapped into application space
interrupt occurs
interrupt handler writes to the kernel address
Those pages being kernel space are always available, but via mmap also
part of the user space
Alan
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