UM0851 datasheet(160/245 Pages) STMICROELECTRONICS

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Accelerator engine device drivers

UM0851

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Doc ID 16604 Rev 2

munmap(adrs, size);

adrs: is address of mapped memory

size: is size of mapped memory

On success zero is returned otherwise, -1 is returned on error and errno is set appropriately.

After unmapping memory, you must close JPEG nodes. Use the following system call to do

this:

close(fd);

Close returns zero on success, or -1 if error occurred, errno is set appropriately. This

function must be called both for read and write nodes.

JPEG codec usage

JPEG read and write are not synchronized enough, for example, one chunk of input data

may produce output data varying in size. Due to this, you need to write and read

simultaneously to JPEG driver, otherwise JPEG codec may be wasting time sitting idle. It is

recommended to use two processes or threads to read and write data simultaneously from

the JPEG driver. This will increase speed of JPEG processing. The following example is for

encoding/decoding a JPEG image. Here input data is read by application from a file and is

passed to JPEG driver. After that, it is processed by JPEG codec based no processing type

(encoding/decoding), and output data is read by application again.

#include <sys/mman.h>

#include "include/linux/spr_jpeg_syn_usr.h"

struct jpeg_info jpeg_info;

volatile unsigned char *wbuf[2] = {NULL, NULL}, *rbuf[2] = {NULL, NULL};

unsigned int wsize = 4*4096, rsize = 4*4096;

unsigned int ssize = XXX;/* set size of input data here */

int rfd, wfd, cur_rbuf = 1, cur_wbuf = 1;

pid_t pid;

void jpegread()

{

int size = 0, status;

/* while encoding/decoding is not over */

{

shuffle_buf(cur_rbuf);

if((status = ioctl(rfd, JPEGIOC_GET_OUT_DATA_SIZE, &size)) != 0)

return -1;

/* Add code here for manipulating decoded data present in rbuf[cur_rbuf] */

}while(size == rsize);

/* get jpeg info after encoding/decoding is over */

ioctl(rfd, JPEGIOC_GET_INFO, &jpeg_info);

/* unmap buf */

munmap((char *)rbuf[0], 2*rsize);

close(rfd);

}

void jpegwrite()

UM0851 Datasheet(PDF) 160 Page - STMicroelectronics

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