Haptic fails to rumble after stdout is used by another call

[geniot]

I'm using SDL2 bindings for GoLang. I'm also cross compiling for a MIPS device (PocketGo handheld console). Strangely when I use stdout haptic stops working. Eg.:

        cmd := exec.Command("amixer", "sget", "Master")
        res, _ := cmd.Output()

It seems that haptic's implementation depends on the usage of stdout. Is there a suggested way to deal with that?

[icculus]

It feels like there might be more going on here. A small test program that reproduces the issue would be very helpful to verify the problem.

[geniot]

Ok, here goes. The GoLang code:

package main

import (
    "github.com/veandco/go-sdl2/sdl"
    "os/exec"
    "strconv"
)

const (
    GCW_BUTTON_L2    = sdl.K_PAGEUP   //rumble
    GCW_BUTTON_R2    = sdl.K_PAGEDOWN //exec output
    GCW_BUTTON_START = sdl.K_RETURN   //quit
)

func main() {
    sdl.Init(sdl.INIT_EVERYTHING)
    window, _ := sdl.CreateWindow(
        "haptic_fail_test",
        sdl.WINDOWPOS_UNDEFINED,
        sdl.WINDOWPOS_UNDEFINED,
        320,
        240,
        sdl.WINDOW_SHOWN|sdl.WINDOW_BORDERLESS)
    defer window.Destroy()

    var haptic *sdl.Haptic
    numHaptics, _ := sdl.NumHaptics()
    if numHaptics > 0 {
        println("Haptics: " + strconv.Itoa(numHaptics))
        println(sdl.HapticName(0))
        haptic, _ = sdl.HapticOpen(0)
        haptic.RumbleInit()
        defer haptic.Close()
    }

    var running = true
    for running {
        for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
            switch t := event.(type) {
            case *sdl.KeyboardEvent:
                if t.State == sdl.PRESSED {
                    if t.Keysym.Sym == GCW_BUTTON_L2 {
                        var err = haptic.RumblePlay(0.33, 500)
                        if err != nil {
                            println(err.Error())
                        }
                    }
                    if t.Keysym.Sym == GCW_BUTTON_R2 {
                        cmd := exec.Command("amixer", "sget", "Master")
                        res, _ := cmd.Output()
                        println(string(res))
                    }
                    if t.Keysym.Sym == GCW_BUTTON_START {
                        running = false
                    }
                }
            }
            break
        }
    }
    sdl.Delay(1000 / 60)

}

The build.sh:

CC='/opt/gcw0-toolchain/usr/bin/mipsel-gcw0-linux-uclibc-gcc' \
 CGO_CFLAGS='-I/opt/gcw0-toolchain/usr/mipsel-gcw0-linux-uclibc/sysroot/usr/include
  -D_REENTRANT' \
 CGO_ENABLED=1 \
 CGO_LDFLAGS='-L/opt/gcw0-toolchain/usr/mipsel-gcw0-linux-uclibc/sysroot/usr/lib -lSDL2' \
 GOARCH=mipsle \
 GOMIPS=softfloat \
 GOOS=linux \
 PKG_CONFIG='/opt/gcw0-toolchain/usr/bin/pkg-config' \
 go build -o tmp/hapticfail.gcw main.go

ldd output:

POCKETGO2V2:/media/data/local/home # ldd hapticfail.gcw 
    libSDL2-2.0.so.0 => /usr/lib/libSDL2-2.0.so.0 (0x77460000)
    libpthread.so.0 => /lib/libpthread.so.0 (0x7743a000)
    libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x77404000)
    libc.so.0 => /lib/libc.so.0 (0x7739e000)
    libm.so.0 => /lib/libm.so.0 (0x77383000)
    libdl.so.0 => /lib/libdl.so.0 (0x7736f000)
    librt.so.0 => /lib/librt.so.0 (0x7735b000)
    ld-uClibc.so.0 => /lib/ld-uClibc.so.0 (0x77573000)

The console log (execution on PocketGo):

POCKETGO2V2:/media/data/local/home # ./hapticfail.gcw 
The path /dev/dri/ cannot be opened or is not available
The path /dev/dri/ cannot be opened or is not available
fbdev_display succesful
Kernel: Vivante GPL kernel driver 4.6.6.1381
Physical address of internal memory: 00000000
* Video memory:
  Internal physical: 0x00000000
  Internal size: 0x00000000
  External physical: 00000000
  External size: 0x00000000
  Contiguous physical: 0x8c7efb00
  Contiguous size: 0x00400000
Succesfully opened device
native_fbdev: 2 buffers of 320x240
Framebuffer format: 6, flip_rb=0
Framebuffer format: 6, flip_rb=0
Haptics: 1
pwm-haptic (0x0,0x0)
Simple mixer control 'Master',0
  Capabilities: volume
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: 0 - 255
  Front Left: 56 [22%]
  Front Right: 56 [22%]

Simple mixer control 'Master',0
  Capabilities: volume
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: 0 - 255
  Front Left: 56 [22%]
  Front Right: 56 [22%]

Haptic: Error updating the effect: Invalid argument
Haptic: Error updating the effect: Invalid argument

I pressed L2 a couple of times to make sure rumble works. Then I pressed R2 - I saw exec output in the console. Then I pressed L2 again (2 times). You can see "Error updating the effect".

On PocketGo I entered the terminal mode (disabled UI). Here is how my screen looks like after all these presses:

5,5,6,5 - five appears on L2, six on R2.

I tried the same without calling cmd.Output():

exec.Command("amixer", "sget", "Master")
//res, _ := cmd.Output()
//println(string(res))

Rumble keeps working. So it's the cmd.Output() call that breaks the Haptic for some reason. Do you have any suggestions how to fix this? Thanks.

[slouken]

SDL 2.0 is now in maintenance mode, and all inactive issues are being closed. If this issue is impacting you, please feel free to reopen it with additional information.