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

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Date:	Thu, 8 Oct 2015 12:31:50 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Mikulas Patocka <mpatocka@...hat.com>,
	Michal Januszewski <spock@...too.org>
CC:	<linux-fbdev@...r.kernel.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	<linux-kernel@...r.kernel.org>
Subject: 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


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