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I am using a bus adapter to allow access from a VME system to a user shared memory segment. The driver for the adapter can not handle physical addresses above 4GB. Unfortunately, I have 16GB in my system. I would like to force the physical memory addresses returned by shmget() to be below the 4GB boundary. This would allow the driver calls to get_user_pages() and ultimately page_to_phys() to return an address that is valid inside of 32-bits. Is there a way to make this happen? I am running RH Linux 2.6.9-67.ELsmp
Angelo Dvorak
angelo.d.dvorak@lmco.com
GFP_DMA32
I don't know of any way for userspace to influence shmget() in that way.
But you can have the driver allocate the memory with GFP_DMA32 and then your multiple processes can mmap() that that ram and share it with the device.
The GFP_DMA32 code went into kernel.org in 2.6.15. RHEL 4 backported a whopping 1100+ patches onto 2.6.9, but this was not one of them.
-Patrick
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