On Friday, October 30, 2020 9:09 AM, Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > On Thu, 29 Oct 2020 21:53:34 +0100 > Marcin Kocur marcin2006@xxxxxxxxx wrote: > > > Hello, > > this is the output of turning off and on my display (using power button): > > ... > > > The monitor was visible in xrandr as DP-2, after power off and on it's > > visible as DP-3 (DP-2 is still there "disconnected"). > > It's troublesome for: > > > > - GUI display configurators > > > > - scripting > > > > - for Xorg configuration which stops to work: > > > > > > Section "Monitor" > > Identifier "DP-2" > > Option "Primary" "true" > > EndSection > > Is this a bug or a feature? > > Hi, > > this is how the kernel DRM sub-system works. The connector names are > not persistent in general, just like you can't expect that the same gfx > card appears always at the same /dev/dri/cardN node if you have > several. By default, cardN nodes are assigned in the order of which > driver instance happens to initialize first and it can be random. > > Usually hard-wired (in hardware) connectors just happen to always be > discovered in the same order, and if you only have a single gfx card in > your machine, the connector naming is practically persistent. This is > an accident. It is not guaranteed if you have multiple cards or you > have MST connectors. > > MST connectors can appear and disappear dynamically. There is a KMS > property that attempts to reflect something about the MST topology so > that you might have some hope to match a "connector", but this is not > in the connector name. The concept of a persistent connector is > problematic if the connector is in a MST monitor for daisy-chaining > more monitors - you can always unplug the first monitor making the > connector disappear (not just become disconnected). > > If you want reliable monitor matching, monitor serial number (if > present) would be a more reliable method. I'm not sure Xorg config has > matching rules for that though, but I suppose RandR based configuration > utilities could do it. > > If you want to discuss this further, dri-devel mailing list is the > place - Cc'd. Nothing to do with systemd here, nor even with udev. If you really want to reliably match the physical connector, this proposal from Ville may help: https://lists.freedesktop.org/archives/dri-devel/2019-June/221902.html In fact, MST connectors already all have a PATH prop. What we're missing is a PATH prop for other connectors as well. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
