We are currently migrating Bugzilla to GitHub issues.
Any changes made to the bug tracker now will be lost, so please do not post new bugs or make changes to them.
When we're done, all bug URLs will redirect to their equivalent location on the new bug tracker.

Bug 5364 - Raspberry pi 4 won't recognize the second display (kmsdrm video driver)
Summary: Raspberry pi 4 won't recognize the second display (kmsdrm video driver)
Status: WAITING
Alias: None
Product: SDL
Classification: Unclassified
Component: *don't know* (show other bugs)
Version: 2.0.12
Hardware: ARM Linux
: P2 normal
Assignee: Ryan C. Gordon
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-11-24 13:13 UTC by svenvd.github
Modified: 2020-11-24 15:37 UTC (History)
1 user (show)

See Also:

Attachments
Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description svenvd.github 2020-11-24 13:13:44 UTC 
Hi,

SDL (SDL_GetNumVideoDisplays) does not recognize the second display on a raspberry pi 4 when running with no X11(kmsdrm video driver). Higher level libraries,like pygame thus can not assign a display for particular output.

More information can be found here.

https://github.com/pygame/pygame/issues/2356

Thanks
Comment 1 Dan Lawrence 2020-11-24 13:31:49 UTC 
You can see that the kmsdrm driver is just assuming a single display here, in multiple lines like this one:

    dispdata = (SDL_DisplayData *)SDL_GetDisplayDriverData(0); //viddata->devindex);

meanwhile other video drivers that do have multi_display support do things like:

    SDL_DisplayData *pData =(SDL_DisplayData*)SDL_GetDisplayDriverData(displayIndex);


Looking back on this thread when the driver was first created:

https://discourse.libsdl.org/t/kms-drm-context-for-the-gl-gles-renderer/21813/11

it seems it was discussed and multiple displays being 'out of scope' was mentioned.
Comment 2 Sam Lantinga 2020-11-24 15:37:16 UTC 
Multiple displays are no longer out of scope. I don't have a test setup for this, does anyone have a patch they'd like considered for inclusion that supports this?