sandeepmhptr Offline

Registered User

Join Date: Nov 2008

Posts: 5

regarding fbset

Hi all,
I need to change the frame buffer resolution by using fbset on arm board having linux image.

when the board has just started the fbset command shows the current resolution as 720x480

I tried to change the resolution using
fbset -xres 40

but the ressolution to which the framebuffer was changed to was 320x240

Afteer that what ever value I give t
fbset -xres
the resolution is 320x240
the resolution does not chnge to previous value of 720x480 also.

I need to change to any resolution
I know that the kernel should support some specific resolutions, but in my case the resolution does not change back to original one also.
and I have only one resolutiion 320x240 to which I can change using fbset.

But I think I need to support more number of resolutions

Kindly suggest some solutions

Regards!
Sandeep Mohapatra

2009-02-06, 10:11 AM CST

sideways Offline

Registered User

Join Date: Oct 2004

Location: London, UK

Posts: 3,505

Are you using a vesa framebuffer? If so then fbset doesn't change settings for that, at least not in Fedora 10.

You don't say which linux you're using, I'll assume it's a fairly recent one. In fedora 10 there is a little utility called vbetest which you can install via yum, that can be used to test vesa modes, then if you find a suitable mode you add it to the kernel boot line in grub as 'vga=xxx' where xxx is the mode number + 512

eg on my machine I get

Code:

[r...@localhost ~]# vbetest
VBE Version 3.0
Intel(r) 82945GM Chipset Family Graphics Chip Accelerated VGA BIOS
[352] 1280x800 (256 color palette)
[353] 1280x800 (5:6:5)
[354] 1280x800 (8:8:8)
[358] 1280x800 (256 color palette)
[359] 1280x800 (5:6:5)
[360] 1280x800 (8:8:8)
[261] 1024x768 (256 color palette)
[279] 1024x768 (5:6:5)
[280] 1024x768 (8:8:8)
[274] 640x480 (8:8:8)
[276] 800x600 (5:6:5)
[277] 800x600 (8:8:8)
[257] 640x480 (256 color palette)
[259] 800x600 (256 color palette)
[273] 640x480 (5:6:5)
Type a mode number, or 'q' to quit -

and I use 'vga=866' in my kernel boot line (354+512) to get 1280x800 console reolution. The (8:8:8) means 24bit color depth

2009-02-09, 05:29 AM CST

sandeepmhptr Offline

Registered User

Join Date: Nov 2008

Posts: 5

fbset

hi I am using a board
ARM 926EJ
on that kernel image loaded is montavista linux 2.6.10
framebuffer is-> viafb framebuffer

I tried with vbetest, and the errror I got was
-sh: vbetest: not found

2009-02-09, 08:50 AM CST

sideways Offline

Registered User

Join Date: Oct 2004

Location: London, UK

Posts: 3,505

vbetest is available in the yum repositories for 32bit fedora (it will not run under x86_64), I don't know about montavista. You could try compiling the sourcecode vbetest.c, you'll need the lrmi library and header files, in fedora you would just type 'yum install lrmi-devel', then to compile the source use

Code:

gcc -o vbetest -llrmi vbetest.c

If you can boot a fedora livecd/usb you could run it from there just to get the supported vesa modes, and then edit grub.conf with the appropriate mode.

You can also pass vga=ask as an option at the grub boot screen, that will list vga text modes and vesa modes, but it sometimes misses some vesa modes (eg on widescreen laptops the 1280x800 modes are often not listed, whereas vbetest will show them)

[linuxkernelnewbies] regarding fbset - FedoraForum.org

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