Sis 315 graphics engine
1 / 16

SiS 315 Graphics Engine - PowerPoint PPT Presentation

  • Uploaded on

SiS 315 Graphics Engine . Introduction to some capabilities of graphics accelerator hardware. SVGA incompatibilities. SVGA manufacturers have different ways of implementing their accelerator features SiS provides 2D and 3D graphics engines Access is via memory-mapped i/o ports

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'SiS 315 Graphics Engine' - maddox

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Sis 315 graphics engine l.jpg

SiS 315 Graphics Engine

Introduction to some capabilities of graphics accelerator hardware

Svga incompatibilities l.jpg
SVGA incompatibilities

  • SVGA manufacturers have different ways of implementing their accelerator features

  • SiS provides 2D and 3D graphics engines

  • Access is via memory-mapped i/o ports

  • This requires a new Linux device-driver, to allow mapping the io-ports into user-space

  • A suitable driver is our ‘engine2d.c’

  • It only works with SiS graphics hardware

Sis policy l.jpg
SiS policy

  • SiS officials say it is not company policy to provide individuals with programming info

  • But some programming info is available in ‘unofficial’ sources (e.g., in-line comments by programmers who wrote ‘open source’ device-drivers for Linux XFree86 systems)

  • Not everything is fully explained, though

  • So a lot of ‘trial-and-error’ is necessary!

Where to look for info l.jpg
Where to look for info

  • The source-code for drivers distributed with the Linux kernel can be found in: /usr/src/local/linux/drivers/video/sis

  • Recent versions of the SVGALIB package have some SiS-specific code you can view

  • There is also a website maintained by the author of the SiS driver for Linux (Thomas Winischhofer):

Linux kernel modules l.jpg
Linux kernel modules

  • Linux permits installing new kernel code at runtime (i.e., without recompiling kernel)

  • A system administrator can install/remove kernel modules, and may grant users this same privilege (by adjusting permissions on the ‘insmod’ and ‘rmmod’ commands)

  • Modules are written in the C language (not C++) and include special header-files that are distributed with the kernel source-code

Module requirements l.jpg
Module requirements

  • Must define __KERNEL__ and MODULE before any #include statements

  • Must have: #include <linux/module.h>

  • Maybe others: e.g., #include <linux/pci.h>

  • Must have these two public functions: int init_module( void ); void cleanup_module( void );

  • Usually device-specific function(s), too

Driver module structure l.jpg
Driver-Module Structure

// filename and module abstract

#include ---------

#define -----------

typedef -------------

static data objects

This is the device-driver core





struct file_operations


These are for module mgmt



Our engine2d c module l.jpg
Our ‘engine2d.c’ module

  • Our module only needs one extra function: int my_mmap( );

  • Also needs a ‘struct file_operations’ object: struct file_operations my_fops;

  • The ‘init_module()’ function will install that structure-object in kernel-space, together with executable code which it references

  • The ‘cleanup_module()’ function removes that code and data after we’re finished

How it works l.jpg
How it works



int $0x80














Pentium s page tables l.jpg
Pentium’s Page-Tables

  • Our driver’s ‘mmap’ method calls a kernel procedure that knows how to setup some new entries in the CPU’s page-directory and page-table data-structures which give the effect of mapping the GPU’s i/o-ports into an application’s virtual address-space

  • Then the program can read or write these i/o-ports as if they were memory-locations

The pci interface l.jpg
The PCI Interface

  • The graphics hardware connects with the CPU using the AGP bus, conforming to a standard PCI-bus programming interface

  • Linux kernel functions can be called from our ‘init_module()’ to query the GPU chip

    • Identify the chip’s make and model

    • Get physical address for its i/o-memory

    • Determine the length of the i/o-memory

Linux device nodes l.jpg
Linux device-nodes

  • Linux treats devices as if they were files

  • We must create a device-file for our GPU

  • Device-files normally go in ‘/dev’ directory

  • We invent a filename for our device-file

  • We pick an unused device id-number

  • A system administrator creates the file: root# mknod /dev/sismmio c 101 0 root# chmod a+rw /dev/sismmio

Our sisaccel cpp demo l.jpg
Our ‘sisaccel.cpp’ demo

  • We have written a short demo-program

  • It uses the SiS 315’s 2D graphics engine

  • It fills some rectangles with a solid color

  • It also shows how to draw a line-segment

  • These operations could be done, as we know, with software algorithms – but it’s faster to let the hardware do it instead

  • You are invited to experiment further!

Include sisaccel h l.jpg
#include “sisaccel.h”

  • This header defines symbolic names for some of the 2D engine’s i/o addresses

  • Accelerator commands involve writing the values for various parameters to these i/o port-addresses, concluding with a value that encodes a desired engine ‘command’

  • Some Extended Sequencer registers must be initialized beforehand, to enable engine

Truecolor graphics l.jpg
Truecolor Graphics

  • We used VESA graphics mode 0x413B

  • Screen-resolution is 800x600

  • Pixels are 32-bits in size (‘Truecolor’)

  • Recall the Truecolor pixel-format:





Alpha channel

Makefile l.jpg

  • In order to compile the ‘engine2d.c’ driver, we recommend using the ‘Makefile’ on our class website (copy it to your directory): $ make engine2d.o

  • Be sure you compile it BEFORE you try to run the ‘gpuaccel.cpp’ demo-program

  • Don’t forget that your IOPL needs to be 3 e.g., run the ‘iopl3’ program first