- Standard fbdev applications that use mmap but that do not
- report damage, may be able to work with this enabled.
- Disabled by default because of overhead and other issues.
-
-console Allow fbcon to attach to udlfb provided framebuffers. This
- is disabled by default because fbcon will aggressively consume
- the first framebuffer it finds, which isn't usually what the
- user wants in the case of USB displays.
+ Standard fbdev applications that use mmap but that do not
+ report damage, should be able to work with this enabled.
+ Disable when running with X server that supports reporting
+ changed regions via ioctl, as this method is simpler,
+ more stable, and higher performance.
+ default: fb_defio=1
+
+console Allow fbcon to attach to udlfb provided framebuffers.
+ Can be disabled if fbcon and other clients
+ (e.g. X with --shared-vt) are in conflict.
+ default: console=1
+
+shadow Allocate a 2nd framebuffer to shadow what's currently across
+ the USB bus in device memory. If any pixels are unchanged,
+ do not transmit. Spends host memory to save USB transfers.
+ Enabled by default. Only disable on very low memory systems.
+ default: shadow=1