KnIoDmaMap()

This function is declared in the coresrv/io/dma.h file.

Retcode KnIoDmaMap(Handle rid, rtl_size_t offset, rtl_size_t length, void *hint,

int vmflags, void **addr, Handle *handle);

This function maps a DMA buffer area to the address space of a process.

Input parameters:

• rid is the handle of the DMA buffer allocated using KnIoDmaCreate().
• offset refers to the page-aligned offset of the start of the area from the start of the buffer, indicated in bytes.
• length refers to the size of the area; it must be a multiple of the page size and must not exceed <buffer size - offset>.
• hint is the virtual address of the start of mapping; if it is equal to 0, the address is selected by the kernel.
• vmflags refers to allocation flags.

In the vmflags parameter, you can use the following allocation flags (vmm/flags.h):

• VMM_FLAG_READ and VMM_FLAG_WRITE are memory protection attributes.
• VMM_FLAG_LOW_GUARD and VMM_FLAG_HIGH_GUARD add a protective page before and after the allocated memory, respectively.

Permissible combinations of memory protection attributes:

• VMM_FLAG_READ allows reading page contents.
• VMM_FLAG_WRITE allows modification of page contents.
• VMM_FLAG_READ | VMM_FLAG_WRITE allows reading and modifying page contents.

Output parameters:

• addr is the pointer to the virtual address of the start of the mapped area.
• handle refers to the handle of the created mapping.

If successful, the function returns rcOk.

For a usage example, see KnIoDmaCreate().

To delete a created mapping, you must call the KnIoClose() function and pass the specified mapping handle in this function.