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I'm writing my own display server as an educational exercise. Where in the Linux kernel tree would I look for documentation on the console's graphical mode?

Basically, as I understand it, Xorg takes over the tty device and also takes over the raw hardware. How can I find documentation on duplicating that action?

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    From the tty side this article might be useful: linuxjournal.com/article/5896. It's dated so I don't know how much has changed but it looks like it would be relevant to your task.
    – slm
    Commented Oct 6, 2013 at 1:59
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    I don't have a full or direct answer so I'm posting as a comment. You may look at the various Wayland compositors that are available. Wayland is seen by many as the technology to supplant/render obsolete Xorg/XFree86. If you're just starting out you may use the study of Wayland as a general study of GUI's on Linux and if you feel like you really should break away from it for some reason, do so then.
    – Bratchley
    Commented Oct 6, 2013 at 1:59
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    Have you poked around here too? kernelnewbies.org
    – slm
    Commented Oct 6, 2013 at 2:01
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    Take a look to the Nano-X sources
    – Alex
    Commented Oct 6, 2013 at 8:13
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    Why don't you just use the framebuffer interface ([src]/Documentation/fb/api.txt)?
    – goldilocks
    Commented Oct 6, 2013 at 11:23

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Sorry for repeating but take a look to Nano-X sources.

git clone git://microwindows.org/microwin

In particular take a look to the files:

drivers/kbd_tty.c
drivers/scr_fb.c

What is done in the tty driver is very similar to what Xorg does, and The devfb driver is a very simple and clean implementation.

Linux's devfb frame buffers mostly rely on ioctl (eg: to set/get resolution) and mmap (to raw write/read pixels).

devfb is just one (easy and a bit more portable on linux) way to access the graphic hardware.

Xorg drivers instead are composed by a kernel driver and a Xorg user space interface between the driver and Xorg itself, and what happen between kernel and user side is really implementation-dependant (there isn't a standard).

You can also take a look to SDL or Directfb but Nano-X is the cleanest/easy and a display server itself, so probably could help you on other question that you'll surely meet.

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