90 lines
2.6 KiB
Plaintext
90 lines
2.6 KiB
Plaintext
What: /dev/memrar
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Date: March 2010
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KernelVersion: Kernel version this feature first showed up in.
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Contact: Ossama Othman <ossama.othman@intel.com>
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Description: The Intel Moorestown Restricted Access Region (RAR)
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Handler driver exposes an ioctl() based interface that
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allows a user to reserve and release blocks of RAR
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memory.
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Note: A sysfs based one was not appropriate for the
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RAR handler's usage model.
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=========================================================
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ioctl() Requests
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=========================================================
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RAR_HANDLER_RESERVE
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-------------------
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Description: Reserve RAR block.
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Type: struct RAR_block_info
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Direction: in/out
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Errors: EINVAL (invalid RAR type or size)
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ENOMEM (not enough RAR memory)
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RAR_HANDLER_STAT
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----------------
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Description: Get RAR statistics.
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Type: struct RAR_stat
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Direction: in/out
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Errors: EINVAL (invalid RAR type)
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RAR_HANDLER_RELEASE
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-------------------
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Description: Release previously reserved RAR block.
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Type: 32 bit unsigned integer
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(e.g. uint32_t), i.e the RAR "handle".
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Direction: in
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Errors: EINVAL (invalid RAR handle)
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=========================================================
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ioctl() Request Parameter Types
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=========================================================
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The structures referred to above are defined as
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follows:
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/**
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* struct RAR_block_info - user space struct that
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* describes RAR buffer
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* @type: Type of RAR memory (e.g.,
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* RAR_TYPE_VIDEO or RAR_TYPE_AUDIO) [in]
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* @size: Requested size of a block in bytes to
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* be reserved in RAR. [in]
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* @handle: Handle that can be used to refer to
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* reserved block. [out]
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*
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* This is the basic structure exposed to the user
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* space that describes a given RAR buffer. It used
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* as the parameter for the RAR_HANDLER_RESERVE ioctl.
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* The buffer's underlying bus address is not exposed
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* to the user. User space code refers to the buffer
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* entirely by "handle".
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*/
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struct RAR_block_info {
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__u32 type;
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__u32 size;
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__u32 handle;
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};
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/**
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* struct RAR_stat - RAR statistics structure
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* @type: Type of RAR memory (e.g.,
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* RAR_TYPE_VIDEO or
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* RAR_TYPE_AUDIO) [in]
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* @capacity: Total size of RAR memory
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* region. [out]
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* @largest_block_size: Size of the largest reservable
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* block. [out]
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*
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* This structure is used for RAR_HANDLER_STAT ioctl.
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*/
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struct RAR_stat {
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__u32 type;
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__u32 capacity;
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__u32 largest_block_size;
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};
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Lastly, the RAR_HANDLER_RELEASE ioctl expects a
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"handle" to the RAR block of memory. It is a 32 bit
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unsigned integer.
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