UM0851 datasheet(154/245 Pages) STMICROELECTRONICS

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Giải thích chi tiết về linh kiện	SPEAr is a family of highly customizable ARM-based embedded

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Accelerator engine device drivers

UM0851

154/245

Doc ID 16604 Rev 2

Figure 41.

JPEG driver framework

The JPEG driver exposes two device nodes to the user application, jpegread and jpegwrite.

You can write input data to the jpegwrite node and get output data from the jpegread node.

You can write/read data to/from jpeg chunk by chunk. This means that you do not need very

big buffers for input and output data. You can take buffers of small size and write/read data

to/from JPEG again and again. The following sections describe usage of JPEG driver in

detail. Note that the sections are in the sequence in which JPEG driver is required to be

programmed.

Using the JPEG codec in Linux

To access the JPEG driver-specific data types in user applications, include

<linux/spr_jpeg_syn_usr.h>. The JPEG device is allocated major number dynamically. To

obtain the major number of the JPEG device, run the following command after board boot-

up:

cat /proc/devices

Character devices:

1 mem

2 pty

3 ttyp

4 /dev/vc/0

4 tty

4 ttyS

5 /dev/tty

5 /dev/console

5 /dev/ptmx

7 vcs

9 st

10 misc

13 input

Linux Char device framework

DMAC

JPEG controller

Kernel

space

Hardware

User

space

JPEG Codec

JPEG controller driver

User application

DMA controller

driver

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