On Sun, Jul 12, 2026 at 9:10 AM Mauro Carvalho Chehab <[email protected]> wrote: > > On Mon, 22 Jun 2026 16:43:35 -0400 > Brian Daniels <[email protected]> wrote: > > > From: Alexandre Courbot <[email protected]> > > > > Add the first version of the virtio-media driver. > > > > This driver acts roughly as a V4L2 relay between user-space and the > > virtio virtual device on the host, so it is relatively simple, yet > > unconventional. It doesn't use VB2 or other frameworks typically used in > > a V4L2 driver, and most of its complexity resides in correctly and > > efficiently building the virtio descriptor chain to pass to the host, > > avoiding copies whenever possible. This is done by > > scatterlist_builder.[ch]. > > > > This version supports MMAP buffers, while USERPTR buffers can also be > > enabled through a driver option. DMABUF support is still pending. > > In practice, USERPTR was used on several drivers that wanted to > share buffers between V4L2 and GPU (so, a previous approach before > DMABUF implementation). > > On my tests with this driver, I was unable use a 1080p camera with > V4L2 and GPU on crossvm. Lower resolutions worked. No idea if this > was a limitation of crossvm (I only used it to test this driver) > or if it is due to a poor MMAP implementation. > > > > > Compliance Testing > > > > This was tested using v4l2-compliance. Since virtio-media serves as > > a proxy to host devices for the guest VMs, we expect the guest > > compliance test to essentially match the host compliance test for the > > same device. > > > > NOTE: v4l2-compliance changes its test behavior depending on the driver > > name. In the guest, the driver name for virtio-media proxied-devices is > > always "virtio-media", even if the actual host device has a driver name > > of e.g. "uvcvideo". To ensure the test is consistent between the host > > and the guest, I created a patch for the v4l2-compliance tool that > > allows you to override the driver name. All test results that follow use > > this patch: > > https://lore.kernel.org/r/[email protected]/ > > As mentioned before, please submit this with their rationale in > separate as a [PATCH v4l-utils] to linux-media ML. > > > > > All tests used a Logitech USB Webcam C925e. > > Please test it displaying inside crossvm - or even better to QEMU if > you manage to add virtio-media support to it. > > Being at QEMU makes a lot easier for everyone to test it.
Hi, Regarding the QEMU support mention, I created this series in QEMU to add the virtio-media PCI device: https://lore.kernel.org/all/[email protected]/ Testing was done using an older driver version at https://github.com/chromeos/virtio-media/tree/main/driver as described in the cover letter. But I can try testing it with this series. Either way, the procedure for using QEMU is in the cover letter, so anyone can try it. BR, Albert. > > > Thanks, > Mauro >
