vfb- what is the purpose of the virtual framebuffer?

Question

I have seen this config flag CONFIG_FB_VIRTUAL=y

• What does it do?
• How does it work?
• What is the relation between vfb and xvfb?

Answer 1

According to this page, it's for testing. It's a framebuffer that's in main memory instead of graphics memory, so you basically can't see it, but if your app environment needs a framebuffer for whatever reason and your hardware doesn't have graphics (not uncommon in embedded apps) then it can be useful.

xvfb is a very different beast. It creates its own virtual framebuffer in userspace for use as an X display. It can be used with programs that need an X connection (e.g. older versions of PhantomJS) but for some reason the system doesn't have an existing X display. It doesn't need any kind of support from the kernel to do this - it uses a framebuffer, but really a framebuffer is just a fancy term for a chunk of memory used for a graphical screen.