Hi
Am 22.05.26 um 16:01 schrieb Icenowy Zheng:
在 2026-05-22五的 15:43 +0200，Thomas Zimmermann写道：
Hi
Am 22.05.26 um 15:28 schrieb Ville Syrjälä:
[...]
But why does your HW use CRTC 1 in the first place.
Could be eg. the enabled outputs can't be driven with CRTC 0.
Yes, for many embedded display solutions the CRTC-connector map is
totally fixed.
I guess what you want to do is pick the first crtc from
modesets[]
which is enabled. Or perhaps even "pick the Nth enabled crtc
from
modesets[] based on the ioctl argument".
The enable-status of each CRTC could change later on, which might
lead
to problems.
Sound like a locking issue if someone is changing the configuration
at the same time we're trying to do the vblank wait here.
I mean that the connected outputs could change at a later point or we
could have multiple CRTCs in use. Today, someone in #intel-gfx
reported
a problem with panning if multiple CRTCs are in use.
Therefore picking a CRTC freely could be a problem. Let's say we
configure modes from one CRTC, but later wait/pan/flush with another
CRTC. I would not trust this to work correctly.
Hence, my suggestion is to select a primary CRTC during the fbdev
client's probe and use it for all later operations until the next
probe
happens. All other CRTCs would mirror the primary one.
What will happen if the "primary CRTC" is then disabled because of no
connected connectors can be driven with it?
This happens during a client hotplug event. We'd re-detect all
connectors, pick the CRTC/output with the lowest spec as new primary and
mirror it to all other connected outputs.
Best regards
Thomas
Thanks,
Icenowy
Best regards
Thomas
Picking the one CRTC/output with the lowest spec and
mirroring it to the others might work. This CRTC would then be
the one
to wait for.
Best regards
Thomas
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809,
AG Nürnberg)
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
