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. > You're able to see the amount of packets per interval by doing a cat > /proc/bus/usb/devices: > > T: Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#= 1 Spd=480 MxCh= 8 > B: Alloc= 0/800 us ( 0%), #Int= 0, #Iso= 0 > > The "B:" line above shows the USB bandwidth usage. Do you need this information to proceed with the patch? --HPS -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
