Enables a direct memory access (DMA) channel.
#include <sys/types.h> #include <sys/errno.h> #include <sys/dma.h>
void d_unmask (channel_id) int channel_id;
| channel_id | Indicates the DMA channel identifier returned by the d_init service. |
The d_unmask service enables the DMA channel specified by the channel_id parameter. A DMA channel must be enabled before a DMA transfer can occur.
The d_unmask kernel service is typically called by a device driver when allocating the resources associated with its device. Some devices require it to be used during normal device operation.
Note: The d_unmask service, as with all DMA services, should not be called unless the DMA channel has been successfully allocated with the d_init service.
The d_unmask kernel service can be called from either the process or interrupt environment.
The d_unmask service has no return values.
The d_unmask kernel service is part of Base Operating System (BOS) Runtime.
The d_complete kernel service, d_init kernel service, d_mask kernel service.
I/O Kernel Services and Understanding Direct Memory Access (DMA) Transfers in AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts.