39 lines
1.5 KiB
ReStructuredText
39 lines
1.5 KiB
ReStructuredText
=============
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Shared Memory
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=============
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Shared memory interfaces are only available with the NuttX kernel
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build (``CONFIG_BUILD_KERNEL=y``). These interfaces support user
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memory regions that can be shared between multiple user processes.
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The user interfaces are provided in the standard header file
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``include/sys/shm.h>``. All logic to support shared memory is
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implemented within the NuttX kernel with the exception of two
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low-level functions that are require to configure the
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platform-specific MMU resources. Those interfaces are described
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below:
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.. c:function:: int up_shmat(FAR uintptr_t *pages, unsigned int npages, uintptr_t vaddr)
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Attach, i.e, map, on shared memory region to a user virtual address.
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:param pages: A pointer to the first element in a array of
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physical address, each corresponding to one page of memory.
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:param npages: The number of pages in the list of physical pages
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to be mapped.
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:param vaddr: The virtual address corresponding to the beginning
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of the (contiguous) virtual address region.
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:return: Zero (OK) is returned on success; a negated errno value is returned on failure.
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.. c:function:: int up_shmdt(uintptr_t vaddr, unsigned int npages)
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Detach, i.e, unmap, on shared memory region from a user virtual address.
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:param vaddr: The virtual address corresponding to the beginning
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of the (contiguous) virtual address region.
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:param npages: T The number of pages to be unmapped.
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:return: Zero (OK) is returned on success; a negated errno value is returned on failure.
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