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

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  Re: [PATCH] uvesafb: make scaling configurable on Nvidia cards Tomi Valkeinen <tomi.valkeinen@ti.com> - 2015-10-08 11:40 +0200
    Re: [PATCH] uvesafb: make scaling configurable on Nvidia cards Mikulas Patocka <mpatocka@redhat.com> - 2015-10-08 14:00 +0200
      Re: [PATCH] uvesafb: make scaling configurable on Nvidia cards Tomi Valkeinen <tomi.valkeinen@ti.com> - 2015-10-08 14:30 +0200
        Re: [PATCH] uvesafb: make scaling configurable on Nvidia cards Mikulas Patocka <mpatocka@redhat.com> - 2015-10-08 16:00 +0200

#1242118 — Re: [PATCH] uvesafb: make scaling configurable on Nvidia cards

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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

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#1242281

On Thu, 8 Oct 2015, Tomi Valkeinen wrote:

> 
> 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

Where do you think that this functionality should be added? To Nouveau? - 
Nouveau can't be used with nVidia binary driver, and this functionality is 
useful especially with nVidia binary driver (it allows to get nice console 
with sharp fonts).

BTW. I don't know if this BIOS function is supported on AMD or not. Could 
someone try it? I don't have an AMD card.

Mikulas
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#1242295

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On 08/10/15 14:51, Mikulas Patocka wrote:

>> 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
> 
> Where do you think that this functionality should be added? To Nouveau? - 
> Nouveau can't be used with nVidia binary driver, and this functionality is 
> useful especially with nVidia binary driver (it allows to get nice console 
> with sharp fonts).

I don't know where is should be. But with a quick look I don't see any
gfx card specific features in uvesafb, and the doc clearly says it's a
generic driver. So if we add this nvidia feature there, shall we add
other features for other cards also? It's a kind of slippery road.

So how does uvesafb work with nvidia driver? uvesafb is used for initial
console, and nvidia driver takes over later when (and if) it's loaded?
And it's not possible to change the scaling via nvidia's driver?

> BTW. I don't know if this BIOS function is supported on AMD or not. Could 
> someone try it? I don't have an AMD card.

Quick googling shows that 0x4f14 might be used by other gfx cards (Epia)
for something else. But I can't really say for sure. So in the minimum I
think the parameter should be renamed to "nvidia_scaling" or similar.

 Tomi

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#1242378

On Thu, 8 Oct 2015, Tomi Valkeinen wrote:

> 
> On 08/10/15 14:51, Mikulas Patocka wrote:
> 
> >> 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
> > 
> > Where do you think that this functionality should be added? To Nouveau? - 
> > Nouveau can't be used with nVidia binary driver, and this functionality is 
> > useful especially with nVidia binary driver (it allows to get nice console 
> > with sharp fonts).
> 
> I don't know where is should be. But with a quick look I don't see any
> gfx card specific features in uvesafb, and the doc clearly says it's a
> generic driver. So if we add this nvidia feature there, shall we add
> other features for other cards also? It's a kind of slippery road.
> 
> So how does uvesafb work with nvidia driver? uvesafb is used for initial
> console, and nvidia driver takes over later when (and if) it's loaded?
> And it's not possible to change the scaling via nvidia's driver?

The nvidia binary driver doesn't handle console, it only handles Xwindow. 
You can use either the VGA 80x25 text console or you can set graphics 
console with uvesafb - in both cases, the video card hardware scales the 
screen and the console font is blurry. The patch allows to turn off the 
scaling.

> > BTW. I don't know if this BIOS function is supported on AMD or not. Could 
> > someone try it? I don't have an AMD card.
> 
> Quick googling shows that 0x4f14 might be used by other gfx cards (Epia)
> for something else. But I can't really say for sure. So in the minimum I
> think the parameter should be renamed to "nvidia_scaling" or similar.

Someone should try the patch on AMD card and say if it can set scaling 
there.

Mikulas

>  Tomi
> 
> 
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