Hi Sarah, Em Tue, 1 Oct 2013 13:45:54 -0700 Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> escreveu: > On Tue, Oct 01, 2013 at 10:01:08PM +0300, Xenia Ragiadakou wrote: > > Hi Sarah, > > > > I read the mail on 'possible conflict between xhci_hcd and a patched > > usbhid'. > > For reference to others: > http://marc.info/?l=linux-usb&m=138064948726038&w=2 > http://marc.info/?l=linux-usb&m=138065201426880&w=2 > > > I looked in xhci and the problem arises in xhci_queue_intr_tx() when > > if (xhci_interval != ep_interval) { > > ... > > urb->interval = xhci_interval; > > } > > > > right? > > Yes. The underlying problem is that the xHCI host sets up the endpoint > contexts during the Configure Endpoint command, using the interval from > the device's endpoint descriptors. It also uses the endpoint descriptor > wMaxPacketSize, which can be wrong as well. If the device driver wants > to use a different urb->interval than is in the endpoint descriptor, the > xHCI driver will simply ignore it. > > (I'm Ccing the linux-media list, as I've discussed some of these devices > with broken descriptors before.) > > > When you say a new API, what do you mean? New functions in usbcore > > to be used by usb device drivers? > > Yes. You would export the function in the USB core, and put a prototype > in a USB include file (probably in include/linux/usb.h). Let's say that > function is called usb_change_ep_bandwidth. > > Drivers could call into that function when they needed to change either > the bInterval or wMaxPacketSize of a particular endpoint. This could be > during the driver's probe function, or before switching alternate > interface settings, or even after the alt setting is in place, but > userspace dictates the driver use a different bandwidth. > > Drivers should pass usb_change_ep_bandwidth a pointer to the endpoint > they need to change, along with the bInterval and wMaxPacketSize values > they would like the endpoint to have. Those values could be stored as > new values in struct usb_host_endpoint. Let me see if I understand the changes at the media drivers. So, please correct me if I got it wrong. I'm yet to get any USB 3.0 media device, although it is common to connect an USB 1.1 or USB 2.0 device on a USB 3.0 host port. So, for example, on this device: Bus 003 Device 002: ID 2040:6600 Hauppauge Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 64 idVendor 0x2040 Hauppauge idProduct 0x6600 bcdDevice 0.69 iManufacturer 16 iProduct 32 HVR900H iSerial 64 4031932745 ... Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x83 EP 3 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0004 1x 4 bytes bInterval 1 ... connected via this BUS device: Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 9 Hub bDeviceSubClass 0 Unused bDeviceProtocol 1 Single TT bMaxPacketSize0 64 idVendor 0x1d6b Linux Foundation idProduct 0x0002 2.0 root hub bcdDevice 3.11 iManufacturer 3 Linux 3.11.2-201.fc19.x86_64 xhci_hcd iProduct 2 xHCI Host Controller iSerial 1 0000:00:14.0 In such situation, and assuming that the USB tables are correct, there's nothing that needs to be done there, as bInterval/wMaxPacketSize are correct for USB 2.0. So, there's no need to call usb_change_ep_bandwidth(). If so, then usb_change_ep_bandwidth() as a quirk, if bInterval or wMaxPacketSize were improperly filled. Right? -- Cheers, Mauro -- 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
