On Monday 23 May 2011 21:47:57 Mauro Carvalho Chehab wrote: > Em 23-05-2011 16:17, Hans Petter Selasky escreveu: > > On Monday 23 May 2011 21:06:32 Mauro Carvalho Chehab wrote: > >> Em 23-05-2011 15:48, Hans Petter Selasky escreveu: > >>> On Monday 23 May 2011 20:14:45 Mauro Carvalho Chehab wrote: > >>>> Em 23-05-2011 11:37, Hans Petter Selasky escreveu: > >>>> > >>>> I don't have any ttusb device here, but I doubt that this would work. > >>> > >>> Hi, > >>> > >>> It is already tested and works fine. > >> > >> This will work for you, but it will likely break for the others. Your > >> patch is assuming that returning an error if selecting alt 1 is enough > >> to know that alt 0 should be used. > >> > >>> What I see is that interface 1 does not have an alternate setting like > >>> the driver code expects, while interface 0 does. So it is the opposite > >>> of what the driver expects. Maybe the manufacturer changed something. > >>> Endpoints are still the same. > >> > >> That sometimes happen. Or maybe you just need a different size. > >> > >>> Please find attached an USB descriptor dump from this device. > >> > >> Int 0, endpoint 0: > >> Interface 0 > >> > >> bLength = 0x0009 > >> bDescriptorType = 0x0004 > >> bInterfaceNumber = 0x0000 > >> bAlternateSetting = 0x0000 > >> bNumEndpoints = 0x0003 > >> bInterfaceClass = 0x0000 > >> bInterfaceSubClass = 0x0000 > >> bInterfaceProtocol = 0x0000 > >> iInterface = 0x0000 <no string> > >> > >> ... > >> > >> Endpoint 2 > >> > >> bLength = 0x0007 > >> bDescriptorType = 0x0005 > >> bEndpointAddress = 0x0082 <IN> > >> bmAttributes = 0x0001 <ISOCHRONOUS> > >> wMaxPacketSize = 0x0000 > >> bInterval = 0x0001 > >> bRefresh = 0x0000 > >> bSynchAddress = 0x0000 > >> > >> ... > >> > >> Interface 0 Alt 1 > >> > >> bLength = 0x0009 > >> bDescriptorType = 0x0004 > >> bInterfaceNumber = 0x0000 > >> bAlternateSetting = 0x0001 > >> bNumEndpoints = 0x0003 > >> bInterfaceClass = 0x0000 > >> bInterfaceSubClass = 0x0000 > >> bInterfaceProtocol = 0x0000 > >> iInterface = 0x0000 <no string> > >> > >> ... > >> > >> Endpoint 2 > >> > >> bLength = 0x0007 > >> bDescriptorType = 0x0005 > >> bEndpointAddress = 0x0082 <IN> > >> bmAttributes = 0x0001 <ISOCHRONOUS> > >> wMaxPacketSize = 0x0390 > >> bInterval = 0x0001 > >> bRefresh = 0x0000 > >> bSynchAddress = 0x0000 > > > > Hi, > > > >> Hmm... assuming that the driver is using ISOC transfers, the difference > >> between alt 0 and alt 1 is that, on alt0, the mwMaxPacketSize is 0 (so, > >> you can't use it for isoc transfers), while, on alt 1, wMaxPacketSize is > >> 0x390. > >> > >> What the driver should be doing is to select an alt mode where the > >> wMaxPacketSize is big enough to handle the transfer. > > > > I can write the code to do that. Summed up: > > > > 1) Search interface 0, for alternate settings that have an ISOC-IN and > > wMaxPacket != 0. Select this alternate setting. > > > > 2) Search interface 1, for alternate settings that have an ISOC-IN and > > wMaxPacket != 0. Select this alternate setting. > > > > 3) Done. > > > > Do you think this will work better? > > > >> Calculating what "big enough" is device-dependent, but, basically, a > >> 480 Mbps USB bus is capable of providing 800 isoc slots per interval. > >> If the packets are bigger, the max bandwidth is bigger. > > > > This is a FULL speed device, max 10MBit/second. > > Hmm... USB 1.1 devices are even more limited on the amount of used > bandwidth. The above procedure is better than the one you've proposed, but > yet you may not be able to receive channels with higher bandwidths. > > The usb "max" limit is lower than the maximum bandwidth. I think that full > speed provides 900 isoc slots per interval, but the interval for usb 1.1 is > higher (1s, while the interval for usb 2.0 is 125 us), but you need to > double check such constraints at the USB 1.1 and 2.0 specs, as I may be > wrong on that, as I read it a long time ago ;) Hi, There are 1000 frames per second when using Full Speed USB. I know the device cannot receive all streams, but it is very well suited for DVB radio. --HPS -- 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
