I'm pleased to announce a USB mini-summit at LinuxCon Vancouver. What: USB mini-summit When: Tuesday, August 16th, all day Where: At the conference venue, room TBD pending confirmation from Angela Brown. Proposed topics include USB virtualization, and improved bandwidth APIs between the USB core and drivers (especially webcam drivers). See the detailed topic list below. Anyone is also welcome to propose or show up with a USB related topic. MUSB? USB 3.0 gadget drivers? USB-IP? The USB mini-summit does overlap with the virtualization mini-summit by a day, but I'm hoping we can schedule talks so some of the virtualization folks can make it to the USB mini-summit. The other option was on Friday during the conference which was not ideal. Proposed topics: Topic 1 ------- The KVM folks suggested that it would be good to get USB and virtualization developers together to talk about how to virtualize the xHCI host controller. The xHCI spec architect worked closely with VMWare to get some extra goodies in the spec to help virtualization, and I'd like to see the other virtualization developers take advantage of that. I'd also like us to hash out any issues they have been finding in the USB core or xHCI driver during the virtualization effort. Topic 2 ------- I'd also like to get the V4L and audio developers who work with USB devices together with the core USB folks to talk about bandwidth management under xHCI. One of the issues is that since the xHCI hardware does bandwidth management, not the xHCI driver, a schedule that will take too much bandwidth will get rejected much sooner than any USB driver currently expects (during a call to usb_set_interface). This poses issues, since most USB video drivers negotiate the video size and frame rate after they call usb_set_interface, so they don't know whether they can fall back to a less bandwidth-intensive setting. Currently, they just submit URBs with less and less bandwidth until one interval setting gets accepted that won't work under xHCI. A second issue is that that some drivers need less bandwidth than the device advertises, and the xHCI driver currently uses whatever periodic interval the device advertises in its descriptors. This is not what the video/audio driver wants, especially in the case of buggy high speed devices that advertise the interval in frames, not microframes. There needs to be some way for the drivers to communicate their bandwidth needs to the USB core. We've known about this issue for a while, and I think it's time to get everyone in the same room and hash out an API. (I will send out an API proposal later this month.) Hope to see you there! Sarah Sharp -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
