kcxt

me trying to understand linux display internals: "huh why does the display panel mode timing struct have a 'hskew' property?"

The doc-comment in the kernel:

Jan 21 at 3:41pmWeb
Show threadOzzelot Jan 21
@cas
blunder
Show threaddmi 💽 Jan 21
@cas i’m not sure i’m following - i’ve coded for at least one memory-mapped framebuffer which had each line aligned to %8, and the concept of horizontal skew makes perfect sense to me? is this something else?
Show threadkcxtJan 21
@domi that sounds like the right usecase, it's used in the qualcomm drivers so clearly it's used for something. it's just funny that whoever wrote the doc comment shared my bemusement at this being a thing for digital displays
Show threaddmi 💽 Jan 21
@cas oh! yeah i think i’ve had the same reaction the very first time, now that i think about it
Show threadSaffron🏳️‍⚧️Jan 21
@domi @cas this and a few other things are residual from analog display technology that stuck around. proprietary implementations are usually way worse in this fashion lol
Show threaddmi 💽 Jan 21
@spinach @cas i wouldn’t call them residual, lots of those values map 1:1 to current concepts. even vblank is still a thing
Show threadSaffron🏳️‍⚧️Jan 21
@domi @cas well yeah there's a good reason they stuck around
Show thread Ada Freya - NeptuwuniumJan 21
@cas If i were to guess this is probably a relic relating to CRT displays
Show threaddakkarJan 21
@[email protected] @cas yes, and X11 modelines
https://www.x.org/releases/current/doc/man/man5/xorg.conf.5.xhtml#:~:text=HSkew%20hskew has a not-terrible explanation
Show threadLilith Ashley Nyx Arson Jan 21
@cas skew?!
Show threadAriadne Conill 🐰Jan 30
@cas this is for analog CRT overscan where there is extra non-visible sections of each line for synchronization. digital signalling does not use this but it still exists for backwards compatibility