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Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 4:39 am
by JetForMe
I'm trying to use SDL2 without X11 or all the overhead of a desktop/window manager. So far I haven't been able to create an SDL2 window, but some helpers online have told me to enable the "Full KMS" driver. I attempted to do so with raspi-config, but there's no option for it, only "legacy" and "fake." They said they were able to select full KMS with the full Buster installer, but I want to avoid that if I can.

I've got the current Buster Lite installed:

Code: Select all

$ raspinfo
System Information
------------------

Raspberry Pi 4 Model B Rev 1.1
PRETTY_NAME="Raspbian GNU/Linux 10 (buster)"
NAME="Raspbian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"

Raspberry Pi reference 2019-07-10
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 175dfb027ffabd4b8d5080097af0e51ed9a4a56c, stage2

Linux rpi4 4.19.66-v7l+ #1253 SMP Thu Aug 15 12:02:08 BST 2019 armv7l GNU/Linux
Hardware	: BCM2835
Revision	: c03111
Serial		: 1000000060018b86
Throttled flag  : throttled=0x50005
Camera          : supported=0 detected=0

Videocore information
---------------------

Aug 15 2019 12:03:51 
Copyright (c) 2012 Broadcom
version 9f8431fb7839c7f00f52b81f5822ddab2b31d0db (clean) (release) (start)

alloc failures:     0
compactions:        0
legacy block fails: 0
Is there a way to get full KMS support without including X11 and all that extra baggage? Thanks!

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 5:08 am
by cjan
in my raspi-config, there is Full KMS option.

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 5:25 am
by JetForMe
Just to be clear…you've got Raspbian Buster Lite dated 2019-07-10 installed?

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 5:31 am
by cjan
JetForMe wrote:
Wed Aug 28, 2019 5:25 am
Just to be clear…you've got Raspbian Buster Lite dated 2019-07-10 installed?
yep, or you can upgrade raspi-config just in case.

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 5:39 am
by JetForMe

Code: Select all

$ sudo apt upgrade raspi-config
Reading package lists... Done
Building dependency tree       
Reading state information... Done
raspi-config is already the newest version (20190709).

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 5:42 am
by cjan
or, edit config.txt
dtoverlay=vc4-fkms-v3d to dtoverlay=vc4-kms-v3d

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 6:12 am
by JetForMe
Alas, that doesn't work. I don't get any of the boot console display, and although I can ssh into the machine, SDL2 won't even initialize now, whereas before it would initialize but fail to create a window. I actually got it to work with fake KMS, but I'd like to get full KMS. I must be missing pieces (or there's more to the config than just that one line).

EDIT: I do see the boot log, but once it gets to what I presume would be the login prompt, the screen goes dark.

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 6:17 am
by JetForMe
I put the middle Raspbian (Raspbian Buster with desktop, but not with recommended software) on another SD card, and that, too, only offers legacy and fake KMS.

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 6:55 am
by 6by9
I'm guessing you're on a pi4. The relevant kernel driver mods have not been made to drive the new hardware via vc4-kms-v3d yet, therefore there is no full option.

Re: Full KMS in Buster Lite?

Posted: Wed Aug 28, 2019 8:14 am
by JetForMe
Ah yes, it’s a Pi 4 (as shown in the output of raspinfo included above). I didn’t realize the distro would lack components for Pi 4.