Documentation/core-api/dma-isa-lpc.rst

12 ------------------------
16 	#include <linux/dma-mapping.h>
19 The first is the generic DMA API used to convert virtual addresses to
20 bus addresses (see Documentation/core-api/dma-api.rst for details).
28 -----------------
37 The DMA-able address space is the lowest 16 MB of _physical_ memory.
45 allocate the memory during boot-up it's a good idea to also pass
52 -------------------
65 Channels  chapter
66 --------
68 A normal ISA DMA controller has 8 channels. The lower four are for
69 8-bit transfers and the upper four are for 16-bit transfers.
72 channel 4 is used to give DMA access for the second controller (0-3).
73 This means that of the four 16-bits channels only three are usable.)
80 The ability to use 16-bit or 8-bit transfers is _not_ up to you as a
82 specs or test different channels.
85 -------------
96 controller that is used for the non-atomic operations. As long as you
105 be 16-bit aligned for 16-bit transfers) and how many bytes to
146 --------------