Re: [PATCH v5] drm/fb-helper: pass physical dimensions to fbdev

[David Lechner]

On 08/04/2017 04:53 PM, Laurent Pinchart wrote:
> Hi David,
>
> Thank you for the patch.
>
> On Friday 04 Aug 2017 11:25:24 David Lechner wrote:
> > The fbdev subsystem has a place for physical dimensions (width and height
> > in mm) that is readable by userspace. Since DRM also knows these
> > dimensions, pass this information to the fbdev device.
>
> I'm curious, what's your use case for this ? What userspace software do you
> use that is still based on fbdev and needs screen dimensions ?


I have dug up an old graphics library called GRX[1] and modernized 
it[2]. So, I am using the screen dimensions to make it DPI-aware so that 
the font on my 2.4" screen looks the same size as my 2.8" screen when 
both are 320x240 pixels. Until this year, all of the displays I have 
only have fbdev drivers.

[1]: http://grx.gnu.de
[2]: https://github.com/ev3dev/grx