inTaskWithOptions
Creates a memory buffer with memory descriptor for that buffer.
Declaration
static OSPtr<IOBufferMemoryDescriptor> inTaskWithOptions(task_t inTask, IOOptionBits options, vm_size_t capacity, vm_offset_t alignment, uint32_t kernTag, uint32_t userTag);Parameters
- inTask:
The task the buffer will be allocated in.
- options:
Options for the allocation:
kIODirectionOut, kIODirectionIn - set the direction of the I/O transfer.
kIOMemoryPhysicallyContiguous - pass to request memory be physically contiguous. This option is heavily discouraged. The request may fail if memory is fragmented, may cause large amounts of paging activity, and may take a very long time to execute.
kIOMemoryPageable - pass to request memory be non-wired - the default for kernel allocated memory is wired.
kIOMemoryPurgeable - pass to request memory that may later have its purgeable state set with IOMemoryDescriptor::setPurgeable. Only supported for kIOMemoryPageable allocations.
kIOMemoryKernelUserShared - pass to request memory that will be mapped into both the kernel and client applications.
kIOMapInhibitCache - allocate memory with inhibited cache setting.
kIOMapWriteThruCache - allocate memory with writethru cache setting.
kIOMapCopybackCache - allocate memory with copyback cache setting.
kIOMapWriteCombineCache - allocate memory with writecombined cache setting.
- capacity:
The number of bytes to allocate.
- alignment:
The minimum required alignment of the buffer in bytes - 1 is the default for no required alignment. For example, pass 256 to get memory allocated at an address with bits 0-7 zero.
- kernTag:
The kernel memory tag.
- userTag:
The user memory tag.
Return Value
Returns an instance of class IOBufferMemoryDescriptor to be released by the caller, which will free the memory desriptor and associated buffer.
Discussion
Added in OS X 10.2, this method allocates a memory buffer with a given size and alignment in the task's address space specified, and returns a memory descriptor instance representing the memory. It is recommended that memory allocated for I/O or sharing via mapping be created via IOBufferMemoryDescriptor. Options passed with the request specify the kind of memory to be allocated - pageablity and sharing are specified with option bits. This function may block and so should not be called from interrupt level or while a simple lock is held.