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

From: David Lechner
Date: Sat Aug 05 2017 - 11:58:03 EST

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.