Re: [PATCH v3] media: add virtio-media driver

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

Em Tue, 17 Jun 2025 11:03:18 +0200
Mauro Carvalho Chehab <mchehab+huawei@kernel.org> escreveu:

> Em Tue, 17 Jun 2025 10:49:38 +0200
> Mauro Carvalho Chehab <mchehab+huawei@kernel.org> escreveu:
> 
> > Hi Alex,
> > 
> > Em Tue, 27 May 2025 23:03:39 +0900
> > Alexandre Courbot <gnurou@gmail.com> escreveu:
> >   
> > > > > > Btw, I was looking at:
> > > > > >
> > > > > >         https://github.com/chromeos/virtio-media
> > > > > >
> > > > > > (I'm assuming that this is the QEMU counterpart, right?)      
> > > > >
> > > > > crosvm actually, but QEMU support is also being worked on.      
> > > >
> > > > Do you have already QEMU patches? The best is to have the Kernel driver
> > > > submitted altogether with QEMU, as Kernel developers need it to do the
> > > > tests. In my case, I never use crosvm, and I don't have any Chromebook
> > > > anymore.      
> > > 
> > > IIRC Albert Esteve was working on this, maybe he can share the current status.    
> > 
> > Any news regards to it?
> >   
> > > Note that crosvm does not require a Chromebook, you can build and run
> > > it pretty easily on a regular PC. I have put together a document to
> > > help with that:
> > > 
> > > https://github.com/chromeos/virtio-media/blob/main/TRY_IT_OUT.md    
> > 
> > I started looking on it today. Already installed crossvm (I had to
> > install libcap-devel to build it). Still, I'm not familiar with
> > crossvm, which is a little be painful. In particular, how can I
> > enable network on it and speedup it? With suggested parameters,
> > it picked only one CPU, and very few memory on it:
> > 
> > 	# cat /proc/cpuinfo|grep processor
> > 	processor       : 0
> > 
> > 	# free
> >                total        used        free      shared  buff/cache   available
> > 	Mem:          221876       34780      139712         272       56096      187096
> > 	Swap:              0           0           0
> > 
> > I'd like to be able to compile things on it and use ssh/scp. So,
> > the VM needs more CPUs, more memory, more network and GPU.

Found how to setup cpus and memory, but didn't find a way to setup
network without running it as root. The gpu parameter has several
options. Not sure what backend works well for media apps like qv4l2,
camorama, X11, ...

> > 
> > Btw, on a quick test with v4l2-compliance, something looks weird:
> > I started a camera application at the host. Still, v4l2-compliance
> > said successfully excecuted mmap:
> > 
> > Streaming ioctls:
> >         test read/write: OK (Not Supported)
> >         test blocking wait: OK
> >         test MMAP (no poll): OK                           
> >         test MMAP (select): OK                            
> >         Vide[2025-06-17T08:44:49.177972817+00:00 ERROR virtio_media::ioctl] VIDIOC_REQBUFS: memory type DmaBuf is currently unsupported
> > [2025-06-17T08:44:49.178164554+00:00 ERROR virtio_media::ioctl] VIDIOC_REQBUFS: memory type DmaBuf is currently unsupported
> > o Capturtest MMAP (epoll): OK                             
> >         test USERPTR (no poll): OK (Not Supported)
> >         test USERPTR (select): OK (Not Supported)
> >         test DMABUF (no poll): OK (Not Supported)
> >         test DMABUF (select): OK (Not Supported)
> > 
> > Which doesn't make any sense, as the host OS should not allow access
> > to mmap while streaming.  
> 
> Ah, this was with the "simple" device, not with the proxy one.
> With the proxy one, I'm getting:
> 
> # v4l2-ctl --all
> Driver Info:
>         Driver name      : virtio-media
>         Card type        : usb video: usb video
>         Bus info         : platform:virtio-media
>         Driver version   : 6.15.0
>         Capabilities     : 0x84200001
>                 Video Capture
>                 Streaming
>                 Extended Pix Format
>                 Device Capabilities
>         Device Caps      : 0x04200001
>                 Video Capture
>                 Streaming
>                 Extended Pix Format
> Priority: 2
> Video input : 0 (Camera 1: ok)
> Format Video Capture:
>         Width/Height      : 1280/720
>         Pixel Format      : 'MJPG' (Motion-JPEG)
>         Field             : None
>         Bytes per Line    : 0
>         Size Image        : 1843200
>         Colorspace        : sRGB
>         Transfer Function : Rec. 709
>         YCbCr/HSV Encoding: ITU-R 601
>         Quantization      : Default (maps to Full Range)
>         Flags             : 
> Crop Capability Video Capture:
>         Bounds      : Left 0, Top 0, Width 1280, Height 720
>         Default     : Left 0, Top 0, Width 1280, Height 720
>         Pixel Aspect: 1/1
> Selection Video Capture: crop_default, Left 0, Top 0, Width 1280, Height 720, Flags: 
> Selection Video Capture: crop_bounds, Left 0, Top 0, Width 1280, Height 720, Flags: 
> Streaming Parameters Video Capture:
>         Capabilities     : timeperframe
>         Frames per second: 30.000 (30/1)
>         Read buffers     : 0
> 
> User Controls
> 
>                      brightness 0x00980900 (int)    : min=-128 max=127 step=1 default=-11 value=-11
>                        contrast 0x00980901 (int)    : min=0 max=255 step=1 default=148 value=148
>                      saturation 0x00980902 (int)    : min=0 max=255 step=1 default=180 value=180
>                             hue 0x00980903 (int)    : min=-128 max=127 step=1 default=0 value=0
> 
> # v4l2-compliance -d0 -s
> 
> Streaming ioctls:
>         test read/write: OK (Not Supported)
>         test blocking wait: OK
>                 fail: v4l2-test-buffers.cpp(1345): node->streamon(q.g_type()) != EINVAL
>         test MMAP (no poll): FAIL
>                 fail: v4l2-test-buffers.cpp(1345): node->streamon(q.g_type()) != EINVAL
>         test MMAP (select): FAIL
>                 fail: v4l2-test-buffers.cpp(1345): node->streamon(q.g_type()) != EINVAL
>         test MMAP (epoll): FAIL
>         test USERPTR (no poll): OK (Not Supported)
>         test USERPTR (select): OK (Not Supported)
> [2025-06-17T08:55:20.768760714+00:00 ERROR virtio_media::ioctl] VIDIOC_REQBUFS: memory type DmaBuf is currently unsupported
>         test DMABUF (no poll): OK (Not Supported)
> [2025-06-17T08:55:20.769745707+00:00 ERROR virtio_media::ioctl] VIDIOC_REQBUFS: memory type DmaBuf is currently unsupported
>         test DMABUF (select): OK (Not Supported)
> 
> At the host, I'm getting:
> 
> Streaming ioctls:
>         test read/write: OK (Not Supported)
>         test blocking wait: OK
>                 fail: ../utils/v4l2-compliance/v4l2-test-buffers.cpp(1346): node->streamon(q.g_type()) != EINVAL
>         test MMAP (no poll): FAIL
>                 fail: ../utils/v4l2-compliance/v4l2-test-buffers.cpp(1346): node->streamon(q.g_type()) != EINVAL
>         test MMAP (select): FAIL
>                 fail: ../utils/v4l2-compliance/v4l2-test-buffers.cpp(1346): node->streamon(q.g_type()) != EINVAL
>         test MMAP (epoll): FAIL
>         test USERPTR (no poll): OK                        
>         test USERPTR (select): OK                         
>         test DMABUF: Cannot test, specify --expbuf-device
> 
> The device I'm using for test is a UVC HDMI capture board:
> 
> 	Bus 005 Device 008: ID 534d:2109 MacroSilicon usb video
> 
> Thanks,
> Mauro



Thanks,
Mauro