Re: [PATCH] uvesafb: make scaling configurable on Nvidia cards

On 03/09/15 00:23, Mikulas Patocka wrote:

[ I sent this some times ago, but didn't get any response ]


Nvidia cards have a BIOS function 0x4f14 that allows to set flat panel
scaling. This patch adds a module parameter "scaling" that uses this
function to set the scaling. By default, the parameter is -1, so that the
driver doesn't attempt to call the scaling function.

This patch is useful when using the binary Nvidia graphics driver - in
that case, the console may be only in text mode or VESA mode. By default,
the video card does scaling that degrades font quality and changes aspect
ratio. This patch makes it possible to turn off the scaling and improve
font quality on the console.

The allowed values depend on VESA BIOS. On my card, the following values
are allowed:
-1	- do not change the scaling
0	- scale to full screen
1, 2	- don't scale
3	- scale and preserve aspect ratio
4	- scale with black border around

Example use:
echo 1 >/sys/module/uvesafb/parameters/scaling; fbset 1280x1024-60 -depth 32 -a
- this sets unscaled 1280x1024 video mode that has much sharper font than
  the scaled modes.

I have to say I don't know much about x86 video, but isn't uvesafb
supposed to be a generic driver? Adding nvidia specific features there
doesn't sound like a right way to handle this.

 Tomi