To initiate a DMA transfer, you need to:
- open GPDMA device node, for example "/dev/edma0.51" (first number is the device number, and second is the channel number)
- query channel for it's capabilities issuing a GPDMA_IOCTL_GETCAPS ioctl passing gpdma_cdev_caps structure
- write() gpdma_cdev_request structure to device
- wait for read() gpdma_cdev_response when transfer is completed or an error occured.
- repeat step 3 as needed.
1 enum gpdma_cdev_buftype {
2 GPDMA_CDEVBUF_BLOCK = 0x1,
3 GPDMA_CDEVBUF_FRAME = 0x2,
4 };
5
6 enum gpdma_cdev_op {
7 GPDMA_FILL = 0x1,
8 GPDMA_COPY = 0x2,
9 GPDMA_XOR = 0x4,
10 };
11
12 struct gpdma_cdev_buffer {
13 int dcb_type;
14 struct iovec dcb_iov;
15 size_t dcb_stride_width;
16 size_t dcb_stride_spacing;
17 };
18
19 struct gpdma_cdev_request {
20 int dcr_op;
21 struct gpdma_cdev_buffer dcr_buffers[8];
22 #define dcr_dst dcr_buffers[0]
23 #define dcr_src dcr_buffers[1]
24 };
25
26 struct gpdma_cdev_response {
27 int drp_status; # errno number
28 };
29
30 struct gpdma_cdev_caps {
31 uint32_t dcc_ops;
32 uint32_t dcc_buffers;
33 };