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Message-ID: <20250618170500.1e60aacf@sal.lan> Date: Wed, 18 Jun 2025 17:05:00 +0200 From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org> To: "Alexandre Courbot" <gnurou@...il.com> Cc: "Albert Esteve" <aesteve@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, "Mauro Carvalho Chehab" <mchehab@...nel.org>, "Hans Verkuil" <hverkuil@...all.nl>, "Jason Wang" <jasowang@...hat.com>, "Xuan Zhuo" <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez <eperezma@...hat.com>, <gurchetansingh@...gle.com>, <daniel.almeida@...labora.com>, <adelva@...gle.com>, <changyeon@...gle.com>, <nicolas.dufresne@...labora.com>, <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>, <virtualization@...ts.linux.dev> Subject: Re: [PATCH v3] media: add virtio-media driver Em Wed, 18 Jun 2025 23:27:13 +0900 "Alexandre Courbot" <gnurou@...il.com> escreveu: > On Tue Jun 17, 2025 at 7:20 PM JST, Mauro Carvalho Chehab wrote: > > Em Tue, 17 Jun 2025 11:03:18 +0200 > > Mauro Carvalho Chehab <mchehab+huawei@...nel.org> escreveu: > > > >> Em Tue, 17 Jun 2025 10:49:38 +0200 > >> Mauro Carvalho Chehab <mchehab+huawei@...nel.org> escreveu: > >> > >> > Hi Alex, > >> > > >> > Em Tue, 27 May 2025 23:03:39 +0900 > >> > Alexandre Courbot <gnurou@...il.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, ... > > I'm afraid getting GPU and graphics in general to work is more involved > and tricky on a regular Linux setup (crosvm was primarily designed for > ChromeOS). If you really need it I can do some more research; most of my > tests have been done using v4l2-ctl or ffmpeg and saving the output on > disk for later inspection. It was actually easier than what I expected, but it had to run as root. Due to that, I had to move it to a test machine that I use just for such kind of tests. I updated it to the Ubuntu version 24.10, but crossvm refused to build even. I end needing to install rust via rustup, as only version 1.81.0 had what it is required to run with the needed features (network, media and gpu). > >> > 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 > > These logs look ok to me: the MMAP tests are failing on the host, so > they are also expected to fail on the guest (still I expect regular > streaming to work on both). USERPTR is not supported on the guest, as > per your request to not support this memory type in new drivers. DMABUF > is not supported at all at the moment. In the specific case of a virtio driver, while it is OK for the first versions to support MMAP only, USERPTR support could make sense, as this is not a real driver for a certain hardware, but instead it is replicating at the guest whatever the host driver has, which may or may not have MMAP. That's said, I don't recall any driver with USERPTR and without MMAP those days. I did a quick check: VB2 devices always seem to have MMAP. - There is one case where only read ioctl is supported: pvrusb2, which is probably not interesting enough those days, but IMHO, for the few cases where a device can't be used at the guest due to the lack of a compatible streaming API, virtio-media should not expose it to the guest and/or issue an error or warning. > If the host cannot pass compliance, the guest will inevitably suffer > from the same shortcomings. :) But at least on the devices I tested I > was still able to stream something onto the disk and the result was > correct. Makes sense. I'll do some tests later and check how it works with a GUI app and some real devices. Regards, Mauro
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