Linux – Setting the video output for the framebuffer device

I can address your question, having previously worked with the Linux FB.

How Linux Does Its FB.

1. First you need to have FrameBuffer support in your kernel, corresponding to your hardware. Most modern distributions have support via kernel modules. It does not matter if your distro comes preconfigured with a boot logo, I don't use one and have FB support.

2. It does not matter if you have a dedicated graphics card, integrated will work as long as the Hardware Framebuffer is supported.

3. You don't need X, which is the the most enticing aspect of having the FrameBuffer. Some people don't know better, so they advocated some form of X to workaround their misunderstandings.

4. You don't need to work with the FB directly, which many people incorrectly assume. A very awesome library for developing with FrameBuffer is DirectFB it even has some basic acceleration support. I always suggest at least checking it out, if you are starting a full-featured FB based project (Web Browser, Game, GUI ...)

Specific To Your Hardware

1. Use the Vesa Generic FrameBuffer, its modules is called vesafb. You can load it, if you have it available, with the commands modprobe vesafb. many distributions preconfigure it disabled, you can check in /etc/modprobe.d/. blacklist vesafb might need to be commented out with a #, in a blacklist-framebuffer.conf or other blacklist file.

2. The Best option, is a Hardware specific KMS driver. The main one for Intel is Intel GMA, not sure what its modules are named. You will need to read up about it from your distro documents. This is the best performing FB option, I personally would always go KMS first if possible.

3. Use the Legacy Hardware specific FB Drivers, Not recommended as they are sometimes buggy. I would avoid this option, unless last-resort necessary.

I believe this covers all your questions, and should provide the information to get that /dev/fb0 device available. Anything more specific would need distribution details, and if you are somewhat experienced, RTFM should be all you need. (after reading this).

I hope I have helped, Your lucky your asking about one of my topics! This is a neglected subject on UNIX-SE, as not everybody (knowingly) uses the Linux FrameBuffer.

NOTE: UvesaFB Or VesaFB?

You may have read people use uvesafb over vesafb, as it had better performance. This WAS generally true, but not in a modern distro with modern Hardware. If your Graphics Hardware supports protected mode VESA (VESA >= 2.0 ), and you have a somewhat recent kernel vesafb is now a better choice.

Since nobody's answered yet, and after tedious hours of googling and testing, I got some grasp of the subject, I'm going to answer it...

Since framebuffer device interface is a quite general one, there could be more fb devices in principle. However, as the VESA driver I used provides a direct connection between a certain hardware device and the framebuffer device file, it doesn't make sense to have more of them than one has real devices.

There's a driver for virtual framebuffer devices, vfb. (Note: different from xvfb which is a virtual framebuffer for X) I haven't tested this myself, but one could have as many fb devices as one wants using the virtual device. I also think that nothing in principle prevents one from piping a virtual device to hardware framebuffer device, allowing to build a framebuffer multiplexer

About the connection between framebuffers and tty's: there is none. The framebuffer is simply drawn to the screen, disregarding anything.

What got me originally confused is the behavior of fbi image viewer. It turns out that it cleverly checks whether the tty it's running in is open or not, and draws to the framebuffer or not according to that. (That's why it refuses to run over SSH, unlike mplayer – it doesn't accept a pseudo terminal.) But the multiplexer-like functionality has got NOTHING to do with the framebuffer itself.

If there's multiple processes writing to framebuffer, they do not block each other. It turns out that my earlier problems (crashes and such) using multiple fb programs simultaneously were not even about the framebuffer at all. Take fbterm terminal and run mplayer from it: no problem. The fbterm and fbcon terminals and the fbi image viewer draw to buffer only when something is updated, so the mplayer dominates the screen virtually 100% of the time. But if you try to run two mplayers, you are going to get a view that flickers showing frames of the one and the other, as they try to draw to the buffer having a race condition.

Some useful links:

http://moi.vonos.net/linux/framebuffer-drivers/

https://www.kernel.org/doc/Documentation/fb/framebuffer.txt