How-to create/use KS Allocators in capture driver

I have written a WDM streaming driver for a capture card and would like to
have my own allocator as I have onboard memory. I’d like to avoid the
memcopy to system memory by making the frames available on the allocator
with the memory mapped to user space. This would be so the SCSI controller
could read directly from my onboard memory. I haven’t seen any examples on
how to do this. Does anyone have any idea of how to make and use
allocators?
Thanks
Jeff


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I’ve never heard of anyone who’s done this, but it shouldn’t be terribly
difficult. In corresponding pin’s KSPIN_DISPATCH table set Allocator
member to allocator table, which contains four callbacks responsible for
allocating and freeing frames (see KSALLOCATOR_DISPATCH).

Beware however that it’s not gauranteed that graph builder will choose to
use your allocator even if you instruct it to do so. For example,
downstream client can insist on its own allocator for performance reasons.
In that case graph builder always opts to use downstream client allocator.
Besides, the docs say that frames allocated by source pin kernel mode
allocator can’t be passsed to user mode (which is unacceptable for capture
driver, I guess).

Max.

xxxxx@pinnaclesys.com wrote:

I have written a WDM streaming driver for a capture card and would like
to
have my own allocator as I have onboard memory. I’d like to avoid the
memcopy to system memory by making the frames available on the allocator
with the memory mapped to user space. This would be so the SCSI
controller
could read directly from my onboard memory. I haven’t seen any examples
on
how to do this. Does anyone have any idea of how to make and use
allocators?
Thanks
Jeff


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