UNX511/DSP912 - Lab 4: I/O Control - The Screen

Due: Sunday, June 9, 2024

In this lab you will make use of I/O control (ioctl) to get screen information. You will use ioctl's to get the fixed screen information and the variable screen information, from which can be derived the visual type, the accelerator (if any), the screen capabilities, the x-resolution, the y-resolution, and bits per pixel. You will direct all error messages to a file.

• The header file for the screen hardware can be included as: linux/fb.h.
  Be sure to include this header file in your C/C++ code.
• The device file for the screen hardware can be found at: /dev/fb0.
• You have to open this file as read only and non-blocking. For a list of open() flags, see Chapter 4 of The Linux Programming Interface.
• You will ask the user to make a selection from one of three options:
     1. Fixed Screen Info
     2. Variable Screen Info
     0. Exit
  
• For fixed screen info, use the ioctl FBIOGET_FSCREENINFO along with the structure
  struct fb_fix_screeninfo. Report the following fixed screen information:
  screen visual (see FB_VISUAL_),
  screen accelerator (see FB_ACCEL_), and
  screen capabilities (see FB_CAP_).
  Report the numbers for these in comments in Lab4.cpp.
• For variable screen info, use the ioctl FBIOGET_VSCREENINFO along with the structure
  struct fb_var_screeninfo. Report the following variable screen information:
  screen xresolution,
  screen yresolution, and
  bits per pixel.
  Report the numbers for these in comments in Lab4.cpp.
• Be sure to run your program as super-user.
• Any errors in the code should be streamed to the standard error channel cerr which should be redirected to a log file called Screen.log using dup2(). You can test your error logging by trying to run your program as a regular user.
• Be sure to make use of Linux's global variable errno by including the header file <errno.h>. The integer variable errno is set by system calls and some library functions in the event of an error to indicate what went wrong. Use errno with strerror() to give a text description of the error, as follows: strerror(errno). Be sure to include <string.h> for strerror(). For instance:
  

      ret = ioctl(.., ..., ...);
      if(ret<0) {
          cerr << strerror(errno) << endl;
      }
          

For documentation on struct fb_fix_screeninfo and struct fb_var_screeninfo, see fb.h.

For documentation on Frame Buffer (screen) ioctl's, see The Frame Buffer Device API.

For a tutorial on I/O control and device drivers in Linux, see Controlling Hardware with ioctls.

Lab Submission:

Be sure to include the numbers for your fixed and variable screen information in your Lab4.cpp.
Email me your Makefile and your Lab4.cpp file to: miguel.watler@senecapolytechnic.ca

NB: My last name is Watler, not Walter.