WIP: Debug failure to call create_buffer_object() on Intel iGPU

[strohel]

Just some WIP debugging to see if I can get just-gl running on Intel iGPU with i915 driver.

Relates to #4.

Currently I'm getting:

prelude

``` [src/main.rs:89] gpu.get_driver().expect("Failed to get GPU driver info") = Driver { name: "i915", date: "20201103", desc: "Intel Graphics", } [src/main.rs:90] gpu.get_bus_id().expect("Failed to get GPU bus ID") = "" Connectors: eDP-1, Connected=✅ HDMI-A-1, Connected=❌ DP-1, Connected=❌ DP-2, Connected=❌ DP-3, Connected=❌ DP-4, Connected=❌ Using connector: eDP-1 Using mode: Mode { name: "1920x1200", clock: 156100, size: (1920, 1200), hsync: (1936, 1952, 2104), vsync: (1203, 1217, 1236), hskew: 0, vscan: 0, vrefresh: 60, mode_type: PREFERRED | DRIVER } [src/main.rs:125] encoder = Info { handle: encoder::Handle( 235, ), enc_type: TMDS, crtc: Some( crtc::Handle( 80, ), ), pos_crtcs: 15, pos_clones: 1, } [src/main.rs:132] crtc = Info { handle: crtc::Handle( 80, ), position: ( 0, 0, ), mode: Some( Mode { name: "1920x1200", clock: 156100, size: ( 1920, 1200, ), hsync: ( 1936, 1952, 2104, ), vsync: ( 1203, 1217, 1236, ), hskew: 0, vscan: 0, vrefresh: 60, mode_type: PREFERRED | DRIVER, }, ), fb: Some( framebuffer::Handle( 289, ), ), gamma_length: 256, } ```

Is AB24 format supported for SCANOUT | WRITE usage: true
Is AR24 format supported for SCANOUT | WRITE usage: true
Is BG24 format supported for SCANOUT | WRITE usage: false
Is BA24 format supported for SCANOUT | WRITE usage: false
Is BX24 format supported for SCANOUT | WRITE usage: false
Is RG24 format supported for SCANOUT | WRITE usage: false
Is R8A8 format supported for SCANOUT | WRITE usage: false
Is RA24 format supported for SCANOUT | WRITE usage: false
Is RX24 format supported for SCANOUT | WRITE usage: false
Is XB24 format supported for SCANOUT | WRITE usage: true
Is XR24 format supported for SCANOUT | WRITE usage: true
gbm.create_buffer_object(width: 1920, height: 1200, format: AR24, usage: SCANOUT | WRITE)
thread 'main' panicked at src/main.rs:155:90:
called `Result::unwrap()` on an `Err` value: Os { code: 22, kind: InvalidInput, message: "Invalid argument" }

Which puzzles me, because the format and usage combination is claimed to be supported.

[mbernat]

Yeah, I don't think the formats are the issue here, we're probably not initializing something else correctly.

It would be nice to get more debug info from DRM/GBM when something goes wrong. With strace you can see a bit more but I'm afraid we'd have to read kernel code to figure out what goes wrong.

[PabloMansanet]

Just to add another data point, I'm having this exact same issue. Will investigate as well!

[PabloMansanet]

I've looked into this for a bit and I didn't really get anywhere. libgbm is a bit underdocumented, and from the examples I find it looks like we should be able to call gbm_bo_create pretty much exactly as we're doing. I might try an equivalent C example tomorrow.