program with frame buffer
Ubuntu 9.10, I have /dev/fb0.
I try a tutorial c source code, and it works on the
embedded board, and works on the PC in my lab as well,
but on my own PC (Ubuntu 9.10) I met the following problem
fd=open("/dev/fb0",O_RDWR); is OK
ioctl(fd,FBIOGET_VSCREENINFO,&vinfo); always fails
My task is to draw a point or line,
and I know something about frame buffer.
Thanks, and here is the output of perror()
Error reading fixed information.
: Bad file descriptor
Then I added printf("fbfd=%d\n",fbfd);
it returned fbfd=-1;
so open() fails ,
I wondered why open() fails, as I said
I have /dev/fb0, so it lacks the right device driver?
vga16fb 12456 0
vgastate 9628 1 vga16fb
fbcon 36640 72
tileblit 2460 1 fbcon
font 8124 1 fbcon
bitblit 5372 1 fbcon
vesafb 5696 1
sorry for my English, this is the first time I post on an English bbs
I change to root, and it works.
$ ls -l /dev/fb0
crw-rw---- 1 root video 29, 0 2009-11-07 21:21 /dev/fb0
On another note, you can still open the file if you add yourself to the group 'video' by placing your name on the 'video' line of /etc/group. For example, to add myself to 'video' on my system, the following line:
This is a much, much safer option than running your program as root, lest you do any permanent damage to your system.
Thanks a lot.
Now I can draw a point, a line and a circle both on the arm board in my lab and on my own computer.
That afternoon I added myself to video group but still failed, so I turned to use sudo .
Today I ran the program without root and succeeded.
And by running the command 'groups', I see 'video'.
I add a new user ,lwhat, and add him to video group, and run 'groups', I cannot see video.
Then I log off and login ,and lwhat is in the group video and of course is able to run the frame buffer program.
I guess I should exit and login to allow the changes to happen.
This is exactly what I want to do. Iwhat, can you provide some more information on how you drew a point, line and circle on the arm and PC?
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