Problem installing the "nouveau" driver

Simon Geard delgarde at ihug.co.nz
Wed Jun 30 02:14:07 PDT 2010


On Tue, 2010-06-29 at 10:25 -0500, alupu at verizon.net wrote:
> With "nouveau", my boot-up goes through these basic steps:
> 
> 1. The original/"regular" console sequence (80x25)

At this point, the display is under BIOS control, running in the default
text mode - the same as for GRUB, and (depending on your hardware), the
BIOS setup screen. Emphasis on the BIOS bit - no video driver involved,
this is entirely between the BIOS chip on the motherboard, and a
counterpart on the video card.

> 2. Nouveau is loaded by UDEV
> 3. At this point, the console goes blank for a sec or so.
>  The preceding messages are wiped out.

At this point, Nouveau takes over the video card from the BIOS - think
of it as rebooting the GPU. Nouveau can make far more effective use of
the card, but it does so very differently.

> 4. The remainder of the boot-up sequence proceeds and stays
> in 240x67 all the way to the prompt (and beyond).
> 5. I can never change the 240x67 resolution of the console
> text mode.

The key thing is that there's no such thing as a 240x67 resolution. What
you have is a combination of 1920x1080 pixels, and a font size that just
happens to fit 240 columns and 67 lines of text - no different from
running a full-screen terminal window under X. So if you want 80x25
under Nouveau (or any other framebuffer driver), you need the kernel to
use the right fonts to achieve that.

The 80x25 mode you boot in is special in that regard, because that
combination of pixels and fonts is implemented in the BIOS itself, as a
standard feature going back 20 years. And being provided by the BIOS,
it's not available if something else is driving the hardware.


An aside: One thing you might have noticed under the NVIDIA binaries. If
you switch from X to a console, it switches back to 80x25, since those
drivers are X only. When you switch back to X, they take over again, and
have to work out what state the hardware is in - occasionally you see
corruption (usually in OpenGL apps), where the drivers haven't gotten it
right. I've once seen black and white patterns reminiscent of a text
console appearing in textures, for example, as if the BIOS had put
something into video memory, and NVIDIA hadn't cleared it out again.

It's a driver bug when it happens, of course, but I mention it to
illustrate the conflict between BIOS and OS driving the hardware.


> BTW, the _exact_ steps of how to set a font in kernel which
> would take effect after "nouveau" is up, will be highly
> appreciated.

I've not tried it myself, but take a look in menuconfig under "Device
Drivers" -> "Graphics Support" -> "Console display driver support" ->
"Select compiled-in fonts". I think that if you pick something like "VGA
8x16", you'll get something like what you want. But like I said, I've
not tried it.

Simon.
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