How do I use KMS mode?

RetroArch General
#1

Hi guys,

I installed RetroArch from the PPA on my Ubuntu 16.04 machine and now I’m trying to figure out how I use RetroArch with KMS mode. If I execute retroarch --features it says that KMS and EGL is supported, does that mean that RetroArch automatically starts in KMS mode if I start it from the console? (I haven’t installed any desktop environments or window managers yet.)

I’d also like to use EmulationStation but I’m not quite sure if I can start Retroarch in KMS mode from EmulationStation…

Can someone give me some info on this? The Wiki entry https://github.com/libretro/RetroArch/wiki/KMS-mode doesn’t really give me the infos I need.

Thanks in advance!

#2

if you have a compatible GPU driver (currently just the open source drivers are compatible with KMS), you should be able to launch RetroArch from an X-less console in DRM/KMS mode. I don’t think EmulationStation works without X, though.

#3

Alright thanks! I’m planning to connect my Retro PC to a CRT TV with the Ultimate SCART Adapter form Arcadeforge, so for my VGA to output 15Khz I’d need xrandr, is there still a way I can use KMS mode with that or do I need a custom EDID to perform that task? Can I use that EDID for 240p AND 480p?

#4

You’d need an EDID, AFAIK (that is, it’s the only solution I found when I sought to have RA via KMS on my arcade cab). Are you sure your TV can do 480p? Most can’t. If you’re doing an EDID, I suggest doing 3840x240 (my GPU would only do 1920x240), which covers most horizontal games/consoles just fine.

Here’s my blog post on creating a custom EDID: http://filthypants.blogspot.com/2014/11/creating-custom-edid-for-arcade-monitor.html

#5

That’s a good point, I’m planning to get a Bang & Olufsen MX 4000 from ebay and from the looks it doesn’t support 480p, but I couldn’t find anything about 480i, the whole CRT topic is relatively new to me… Apart from that I’ve already read that blog post of yours which is very detailed so thank you for that!

In the end my plan is to have a Retro PC connected to my CRT TV via the UMSA, which can use RetroArch in KMS mode and Dolphin + PCSX2 via an X server, I’m just not sure if the X server and the EDID can work well together . This could work theoretically, right?

#6

Yeah, should be fine, I think, though it’ll be a hassle hopping between X and no X.

#7

Indeed, but since there is no PCSX2 core and the Dolphin core didn’t work last time I tried there is no other way than switching X on and off.

Except if I also used X for RetroArch but I really wanted to use KMS mode, else I could switch to Windows and use the CRT_Emu driver and spare me the hassle of creating an EDID.

#8

I was never able to get CRT_Emu driver to cooperate when I tried it. I found xrandr plus an online modeline calculator to be a much easier way of handling that stuff. There was less black-box-magic involved.

#9

Yeah I also prefer Linux for all possible scenarios, I’ve also reconsidered about getting a NEC MultiSync FE2111SB-BK instead (found an auction on ebay starting at 1€), so I don’t have to fiddle around with 15Khz and don’t have to get the UMSA. So all I’d have to do is write a script to stop the X server when I use RetroArch and then start it again as soon as the process ends.

Do you know how well the current Dolphin core works? I’ve seen some commits happening in August, is it being actively developed again? Because if that’s the case, I’d maybe even switch to playing PS2 games on my PS3 so I could even use Lakka on my Retro PC.