Question about hotplugging

Michel Dänzer michel at
Wed Aug 29 08:31:51 UTC 2018

On 2018-08-28 5:55 p.m., Mark van Rossum wrote:
> On my laptop I use Xorg with the intel driver on Debian.
> When I hotplug my 2560x1600 monitor, the desktop switches to that monitor.
> When I hotplug my 2560x1440 monitor, the desktop gets extended.
> Logs:
> Xorg (==) intel(0): Display hotplug detection enabled
> ....
> /usr/lib/gdm3/gdm-x-session: (II) intel(0): resizing framebuffer to
> 2560x1600
> /usr/lib/gdm3/gdm-x-session[2975]: (II) intel(0): switch to mode
> 2560x1600 at 59.9 on DP1 using pipe 0, position (0, 0), rotation normal,
> reflection none
> However, when I plug in a 2560x1440:
> gdm-x-session[1788]: (II) intel(0): resizing framebuffer to 4480x1440
> gdm-x-session[1788]: (II) intel(0): switch to mode 2560x1440 at 60.0 on DP1
> using pipe 1, position (1920, 0), rotation normal, reflection none
> This latter behaviour is not desired as it leads to occasional crashed.
> Question:
> - who does the mode-switching? (Xorg, driver, xinerama, gdm?)
> - how can I change the behaviour, so that when I hotplug the 2560x1440
> monitor, the framebuffer becomes 2560x1440 and not 4480x1440

It's up to your desktop environment. Xorg merely sends hotplug events to
interested clients, it doesn't automatically change the configuration in
any way.

Earthling Michel Dänzer               |     
Libre software enthusiast             |             Mesa and X developer

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