Fix support linux + riscv64

[lab37]

go build
        package github.com/AlexxIT/go2rtc
        imports github.com/AlexxIT/go2rtc/internal/v4l2
        imports github.com/AlexxIT/go2rtc/pkg/v4l2/device: C source files not allowed when not using cgo or SWIG: 
        videodev2_arch.c

[AlexxIT]

What's your hardware? Do you need V4L2 or I can just disable it?

[lab37]

This hardware: https://www.bit-brick.com/
bit_brick_k1 board
os: bianbu
No need V4L2, but I have no idea about how to disable it.
thank you very much.

[nakata5321]

Hi, I want to do the same—create a port for RISC-V.

I have a StarFive VisionFive 2 board running Ubuntu 24.04, which I installed from this source.

I tried building the binary on my board by following the GitHub Actions workflow but encountered the same error:

go build -ldflags "-s -w" -trimpath
        package github.com/AlexxIT/go2rtc
        imports github.com/AlexxIT/go2rtc/internal/v4l2
        imports github.com/AlexxIT/go2rtc/pkg/v4l2/device: C source files not allowed when not using cgo or SWIG: 
        videodev2_arch.c

To fix this, I set the environment variable:

export CGO_ENABLED=0

as done here.

However, I then ran into an issue with the V4L2 package.

From what I understand, in order to build this package, I need to provide a file named videodev2_riscv64.go, similar to how it's done for other platforms.

But I’m unsure where to find the necessary information to create this file.
@AlexxIT, could you help me understand where to get the details used in videodev2_<PLATFORM>.go files?

I’m not sure if I absolutely need the V4L2 package at this stage, but I’d like to compile a fully functional binary.

P.S. for now to build binary I copy all data from videodev2_arm.go to videodev2_riscv64.go and it seems fine.

[AlexxIT]

If you want V4L2 support on riscv64 - you should build helper binary and run it on your platform
https://github.com/AlexxIT/go2rtc/blob/master/pkg/v4l2/device/README.md

Binary will output content of videodev2_<PLATFORM>.go file.

[AlexxIT]

Fixed in master version.

[nakata5321]

If you want V4L2 support on riscv64 - you should build helper binary and run it on your platform https://github.com/AlexxIT/go2rtc/blob/master/pkg/v4l2/device/README.md

Binary will output content of videodev2_<PLATFORM>.go file.

Got it!

Create this file and make PR with it - #1651