Cancel DMA operation.

I've met a problem associats with DMA, i want to receive data from UART through DMA, and store the data into a buffer in on_chipram.

As the handbook says, the alt_dma_rxchan_ioctl() function must been called correctly before can receive data. downside is my program, i don't know is it proper to call the function in that way, at least it doesn't work!

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#include <stdio.h># include <stddef.h># include <stdlib.h># include "sys/alt_dma.h"# include "alt_types.h"# include <system.h>

/* flag used to indicate the transaction is complete */

volatile int dma_complete = 0;

/* function that is called when the transaction completes */

void dma_done (void* handle, void* data)

{

dma_complete = 1;

}

int main (void)

{

alt_u8 buffer[32];

alt_dma_rxchan rx;

FILE *fp;

fp=fopen("dev/uart","r");

/* Obtain a handle for the device */

if ((rx = alt_dma_rxchan_open ("/dev/dma")) == NULL)

{

printf ("Error: failed to open device\n");

exit (1);

}

else

{

/* Post the receive request */

if (alt_dma_rxchan_ioctl(rx,ALT_DMA_RX_ONLY_ON ,NULL)<0)

printf("error set\n");

if (alt_dma_rxchan_prepare (rx, buffer, 32, dma_done, NULL) < 0)

{

printf ("Error: failed to post receive request\n");

exit (1);

}

/* Wait for the transaction to complete */

while (!dma_complete);

printf ("Transaction complete\n");

alt_dma_rxchan_close (rx);

}

return 0;

}

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